[PATCH] WIP: drm/dp_mst: Add support for dumping topology ref histories from debugfs
Lin, Wayne
Wayne.Lin at amd.com
Wed Mar 16 10:46:11 UTC 2022
[Public]
> -----Original Message-----
> From: Lyude Paul <lyude at redhat.com>
> Sent: Wednesday, March 16, 2022 8:48 AM
> To: Lin, Wayne <Wayne.Lin at amd.com>
> Cc: dri-devel at lists.freedesktop.org; amd-gfx at lists.freedesktop.org
> Subject: Re: [PATCH] WIP: drm/dp_mst: Add support for dumping topology ref histories from debugfs
>
> (Adding this back to the dri-devel mailing list since I didn't notice it got
> dropped from there)
>
> Hm, some comments on this issue down below. Sorry for the delayed response, I
> was going to try this right after I finished the MST legacy removal but that's
> ending up taking longer than I hoped.
>
> On Tue, 2022-03-08 at 01:46 +0000, Lin, Wayne wrote:
> > [AMD Official Use Only]
> >
> > Oops...
> > I didn't notice that I replied to wrong mail previously : P
> > Sorry for the confusion and reply to the correct thread.
> >
> > Good day!
> > I probably know why you can't reproduce the issue there. Please refer to the
> > attached
> > patch file which makes me easier to explain this.
> >
> > In dm_dp_mst_get_modes(), we will create a new dc_sink by calling
> > dc_link_add_remote_sink() and add that dc_sink into the array dc_link-
> > >remote_sinks[].
> > However, if we find that aconnector->dc_sink is not null, then we won't
> > create a new
> > dc_sink for that aconnector and won't add the sink to the array dc_link-
> > >remote_sinks[].
> >
> > When the issue that I mentioned before occurs, we won't be able to release
> > the dc_sink
> > for the aconnector when we unplug the sst monitor. Hence, we can't create
> > new dc_sink
> > for the latter on connected new stream sink of that port. Which leads to two
> > issues
> > 1. Unplug monitor and plug in another monitor "to the same port"
> > => Since we use the same dc_sink to reflect the capability of the new
> > connected stream
> > sink, we might send out inappropriate stream to the new connected sink.
> > 2. Because we can't release dc_sink in the array dc_link->remote_sinks[],
> > when we
> > plug/unplug sst monitor to more than 4 different mst port, we will break the
> > criteria
> > "dc_link->sink_count >= MAX_SINKS_PER_LINK" in
> > link_add_remote_sink_helper().
>
> Ok, a lot of this seems to be happening in amdgpu which certainly explains why
> I had so much trouble following along with this originally (also, having
> learned a bit more about how DC works definitely has helped a bit). I already
> see a bunch of issues though with how this code is structured that would
> definitely break things, though note I haven't sat down and tried this on a
> real machine yet - will try tomorrow.
>
> So - it seems like dc_sink == a bunch of hotplugging state for a dm connector,
> which actually tells me for one that this is definitely the wrong spot for
> this code. get_modes() really should just handle filling out DRM modes and
> pretty much nothing else, because callers from DRM aren't going to expect
> side-effects like this when get_modes() is called - which could potentially
> lead to all sorts of weirdness down the line if the DRM call paths that use
> this ever change. i915 and nouveau have good examples of what these functions
> should typically look like, and amdgpu actually seems to mostly follow this
> advice for it's other get_modes() callback.
>
> Note there's also another problem here: the assumption "no EDID ==
> disconnected" isn't correct. It's totally possible to run into EDID-less
> displays if the display is some ancient pre-historic relic, or if the ROM (or
> EEPROM? can't remember what type of chip computer displays tend to use...) chip
> in the monitor containing the EDID has died. Note that the second situation is
> suprisingly more common then one might think! I ran into a 140Hz 4k ASUS
> display where this happened, and I know another friend of mine who had the ROM
> in their display die randomly as well.
>
> So with this being said: I, think the solution here is actually just to
> add/remove dc_sink from dm_dp_mst_detect() based on the CSN, and drop the
> calls from get_modes()? detect() should always be called before the connector
> has been removed, and we could use the return status from
> drm_dp_mst_detect_port() in order to tell whether or not we should add/remove
> the dc_sink.
Thank you Lyude for guiding me through! After your elaboration, I think I roughly
know the idea from drm perspective now. Let me get through this and will get back
to you.
>
> If you don't get to it first tomorrow, I'll see if I can reproduce this
> locally and try writing up a patch.
>
> Also a final note: I don't think it's a good idea in general for there to be a
> fixed size array of dc_sinks like this. Those probably should just be stored
> somehow on a per-connector basis. I say this because in addition to the fact
Understand and agree with that. I plan to remove the constraint as well. Thanks!
> MST connectors aren't destroyed immediately (which could lead to a situation
> where we have more then 6 connected MST ports briefly before their destructors
> run, e.g. during suspend/resume reprobing).
>
> Also, one question below:
> >
> > Anyway, these are my steps to reproduce the issue.
> > I use a startech mst 1to4 mst hub, a sst monitor and a mst monitor.
> >
> > 1. boot up with sst monitor connected to the hub and plug the hub to the
> > system.
> > 2. unplug/plug sst monitor to all left three different DP output ports.
> > Which is used to
> > Pollute all four aconnectors to have them keep the stale dc_sinks.
> > 3. plug in the mst monitor to arbitrary ports. Since the new connected mst
> > monitor will
> > have us add new mst port to the topology and attach a new aconnector for
> > that mst port,
> > we'll try to create a new dc_sink to that new aconnector and break the
> > sink_count
> > limitation. As you can see in the log the error message : "*ERROR* Unable to
> > add a
> > remote sink"
> >
> > (Note that different hub might influence the result. Some hubs will pull
> > down the HPD
> > when there is no monitor connected to its downstream ports which will run
> > into different
> > code flow)
>
> by "pull down" I assume you mean doing a long HPD instead of short (or vice
> versa?).
Yes, long HPD!
Thanks for your help Lyude!
>
> >
> > I also attach the dmesg log under different debug level (0x104 & 0x116) for
> > your reference.
> >
> > Please let me know if you can reproduce then : )
> >
> > Sorry about that Lyude and hope this time I send to the right thread..
> > Really appreciate for your help!!!
> >
> > Regards,
> > Wayne
> > > -----Original Message-----
> > > From: Lyude Paul <lyude at redhat.com>
> > > Sent: Wednesday, March 2, 2022 9:10 AM
> > > To: Lin, Wayne <Wayne.Lin at amd.com>
> > > Subject: Re: [PATCH] WIP: drm/dp_mst: Add support for dumping topology ref
> > > histories from debugfs
> > >
> > > Ran into some issues with my system yesterday (hooray being the first to
> > > find
> > > a rather annoying zsh bug that broke my scripts!), but I've finally got
> > > things
> > > setup. I'm not able to reproduce this issue though (I've tried hotplugging
> > > the
> > > way you mentioned here, but nothing seems to leak), which makes me think
> > > there's something special in your setup we might not have noticed.
> > >
> > > Do you think you could get some drm logs with drm.debug=0x116
> > > log_buf_len=50M
> > > from when this happens so I can get a better idea of the drm events
> > > leading up
> > > to this? Also, if you've been testing this in a GUI could you confirm
> > > whether
> > > this happens when you're just in a plain old VT?
> > >
> > > On Mon, 2022-02-28 at 16:43 -0500, Lyude Paul wrote:
> > > > Alright - starting to look into this now and setting up a system to try
> > > > reproducing this, will let you know as soon as I've got results. Sorry
> > > > again
> > > > about all of the delays
> > > >
> > > > On Fri, 2022-02-25 at 15:47 -0500, Lyude Paul wrote:
> > > > > I didn't get a chance yet, but I've gotten through most of my backlog
> > > > > now.
> > > > > Sorry about the delay - I've been catching up since I had to take two
> > > > > weeks
> > > > > off work very unexpectedly. I'll put aside time to look at this first
> > > > > thing
> > > > > monday.
> > > > >
> > > > > On Fri, 2022-02-25 at 01:33 +0000, Lin, Wayne wrote:
> > > > > > [AMD Official Use Only]
> > > > > >
> > > > > > Hi Lyude,
> > > > > >
> > > > > > Good day!
> > > > > > Sorry to bother you, but would like to know if you can reproduce the
> > > > > > issue?
> > > > > >
> > > > > > Thanks!
> > > > > >
> > > > > > Regards,
> > > > > > Wayne
> > > > > >
> > > > > > > -----Original Message-----
> > > > > > > From: Lyude Paul <lyude at redhat.com>
> > > > > > > Sent: Thursday, February 3, 2022 4:12 AM
> > > > > > > To: Lin, Wayne <Wayne.Lin at amd.com>
> > > > > > > Cc: dri-devel at lists.freedesktop.org
> > > > > > > Subject: Re: [PATCH] WIP: drm/dp_mst: Add support for dumping
> > > > > > > topology
> > > > > > > ref
> > > > > > > histories from debugfs
> > > > > > >
> > > > > > > JFYI I should be able to respond to this soon, I think I'm
> > > > > > > following
> > > > > > > your
> > > > > > > issue a bit more (haven't gotten to go through the patches too so
> > > > > > > I'm
> > > > > > > probably
> > > > > > > going to see if I can reproduce it locally as well. Sorry for the
> > > > > > > delay
> > > > > > > -
> > > > > > > dealing with some X.org stuff and work issues at the moment
> > > > > > >
> > > > > > > On Tue, 2022-01-25 at 08:32 +0000, Lin, Wayne wrote:
> > > > > > > > [Public]
> > > > > > > >
> > > > > > > > Hey Lyude,
> > > > > > > >
> > > > > > > > Sorry, just got chance to get back to this and BIG THANKS to
> > > > > > > > elaborating
> > > > > > > > in
> > > > > > > > such details!
> > > > > > > > Following are some of my comments : )
> > > > > > > >
> > > > > > > > > -----Original Message-----
> > > > > > > > > From: Lyude Paul <lyude at redhat.com>
> > > > > > > > > Sent: Wednesday, January 19, 2022 9:59 AM
> > > > > > > > > To: Lin, Wayne <Wayne.Lin at amd.com>
> > > > > > > > > Cc: dri-devel at lists.freedesktop.org
> > > > > > > > > Subject: Re: [PATCH] WIP: drm/dp_mst: Add support for dumping
> > > > > > > > > topology
> > > > > > > > > ref
> > > > > > > > > histories from debugfs
> > > > > > > > >
> > > > > > > > > Hey - so, the original issue here was that payloads were not
> > > > > > > > > always
> > > > > > > > > deleted when we expected them to be - correct?
> > > > > > > >
> > > > > > > > Actually, what I was trying to do is not relevant to payload
> > > > > > > > maintenance.
> > > > > > > > What I wanted to do is having a way to notify
> > > > > > > > amdgpu to release its enumerated resource "dc_sink" when unplug
> > > > > > > > event
> > > > > > > > occurs. Currently, under specific scenarios,
> > > > > > > > we can't release remote "dc_sink" and ends up can't allocate
> > > > > > > > resource
> > > > > > > > for
> > > > > > > > new connected monitors. I'll explain the scenario
> > > > > > > > underneath.
> > > > > > > >
> > > > > > > > So, get back to the main issue that I was trying to solve when I
> > > > > > > > pushed
> > > > > > > > the
> > > > > > > > patchset:
> > > > > > > >
> > >
> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.kernel.org%2Fproject%2Fdri&data=04%7C01%7Cw
> ayne.lin%40amd.com%7Cd77e829cfd3a466e25e508da06e6a9dd%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637829885024
> 474689%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sda
> ta=MvKilTT1CkBqZVK1N24JyNPjiPYORV%2FsCwvEzwx%2FIAk%3D&reserved=0
> > > ayne.lin%40amd.com%7Cbbc27043edc04bf8067c08d9fbe9620c%7C3dd8961fe4884e608e
> > > 11a82d994e183d%7C0%7C0%7C6378178020798
> > > 98960%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6
> > > Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdat
> > > a=RVUc8KgTO3mhFL9qemshHJqiyXJs%2Fvytx21AMyUaW%2Bs%3D&reserved=0
> > > > > > > > -
> > > > > > > devel%2Fcover%2F20210720160342.11415-1-
> > > > > > > Wayne.Lin%40amd.com%2F&data=04%7C01%7Cwayne.lin%40amd.com%7C2e
> > > > > > > 19d9
> > > > > > > 32
> > > > > > > 1b
> > > > > > > 5f4e948c1208d9e6884f24%7C3dd8961fe488
> > > > > > > 4e608e11a82d994e183d%7C0%7C0%7C637794295422403301%7CUnknown%7CTWFp
> > > > > > > bGZs
> > > > > > > b3
> > > > > > > d8
> > > > > > > eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiL
> > > > > > > CJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=rvtwQioO3pT1BoHb7S5
> > > > > > > 32ms
> > > > > > > Ra
> > > > > > > 61
> > > > > > > gP1vIyE8AB7M9I4E%3D&reserved=0
> > > > > > > >
> > > > > > > > I was trying to fix some problems that I observed after these 2
> > > > > > > > patches
> > > > > > > > * 09b974e8983 drm/amd/amdgpu_dm/mst: Remove -
> > > > > > > > >destroy_connector()
> > > > > > > > callback
> > > > > > > > * 72dc0f51591 drm/dp_mst: Remove
> > > > > > > > drm_dp_mst_topology_cbs.destroy_connector
> > > > > > > >
> > > > > > > > With above patches, it changes our flow to remove dc_sink (by
> > > > > > > > calling
> > > > > > > > dc_link_remote_sink()) when connector is about to be
> > > > > > > > destroyed. And let's see below use cases:
> > > > > > > > a). Disconnection happens between mst branch devices
> > > > > > > > e.g.
> > > > > > > > src - 1st_mstb - 2nd_mstb - sst_monitor => src - 1st_mstb
> > > > > > > > (disconnect)
> > > > > > > > 2nd_mstb - sst_monitor
> > > > > > > >
> > > > > > > > In above case, after receiving CSN, we will put topology
> > > > > > > > reference
> > > > > > > > count
> > > > > > > > of
> > > > > > > > 2nd mstb and its port which connected to the sst monitor.
> > > > > > > > As you suggested before, we will destroy 2nd mst branch device
> > > > > > > > and
> > > > > > > > its
> > > > > > > > all
> > > > > > > > ports due to there is no more mst path can route to them.
> > > > > > > > As the result of that, we at end call
> > > > > > > > drm_dp_delayed_destroy_port()
> > > > > > > > and
> > > > > > > > unregister/put the drm connector and eventually call
> > > > > > > > dc_link_remote_sink() to release the dc_sinck we enumerate for
> > > > > > > > the
> > > > > > > > specific
> > > > > > > > stream sink of sst_monitor.
> > > > > > > >
> > > > > > > > However, in below case:
> > > > > > > > b). Disconnection happens between mst branch devices and SST
> > > > > > > > monitor
> > > > > > > > e.g.
> > > > > > > > src - 1st_mstb - sst_monitor => src - 1st_mstb (disconnect)
> > > > > > > > sst_monitor
> > > > > > > >
> > > > > > > > In this case, which is the case having problem, it definitely
> > > > > > > > won't
> > > > > > > > decrease
> > > > > > > > the topology references count of the port of 1st_mstb which
> > > > > > > > was connected to the sst monitor to zero since the port is still
> > > > > > > > existing in
> > > > > > > > the topology. Same as the malloc reference since the port can't
> > > > > > > > get
> > > > > > > > destroyed. Hence, the port still exists and we won't call
> > > > > > > > drm_dp_delayed_destroy_port() to unregister and put the drm
> > > > > > > > connector.
> > > > > > > > As
> > > > > > > > the
> > > > > > > > result of that, we can't release corresponding remote dc_sink
> > > > > > > > under
> > > > > > > > this
> > > > > > > > case. And after few times hotplugs, we can't create any new
> > > > > > > > dc_sink since the number of stream sink is exceeding our
> > > > > > > > limitation.
> > > > > > > >
> > > > > > > > Hence, what I'm thinking here is to register a callback function
> > > > > > > > for
> > > > > > > > notifying us that the remote sink is detached. This just aligns
> > > > > > > > what
> > > > > > > > we
> > > > > > > > do
> > > > > > > > for handling long HPD event (unplug monitor from system) of
> > > > > > > > legacy
> > > > > > > > DP
> > > > > > > > (none
> > > > > > > > mst). For which case, once we detect long HPD event
> > > > > > > > indicating the monitor is detached, we will immediately try to
> > > > > > > > release
> > > > > > > > the
> > > > > > > > dc_link->local_sink and fire hotplug event to upper layer.
> > > > > > > > Same as here, once receives a CSN message notifying a drm
> > > > > > > > connector
> > > > > > > > is
> > > > > > > > changed from connected to disconnected, trigger the callback
> > > > > > > > function and we can try to release the dc_sink resource.
> > > > > > > >
> > > > > > > > >
> > > > > > > > > If I'm remembering that correctly, then (and I'm not 100% sure
> > > > > > > > > on
> > > > > > > > > this
> > > > > > > > > yet) I might already have noticed something very possibly
> > > > > > > > > wonky in
> > > > > > > > > how we handle payload allocations currently, that I found
> > > > > > > > > while
> > > > > > > > > working on
> > > > > > > > > the non-atomic removal branch that I linked to you in my
> > > > > > > > > previous response. Basically, in the
> > > > > > > > > step1() function it looks like that we follow this general
> > > > > > > > > flow
> > > > > > > > > with
> > > > > > > > > updating
> > > > > > > > > payloads:
> > > > > > > > >
> > > > > > > > > * Loop through proposed payloads and compare to previously
> > > > > > > > > programmed
> > > > > > > > > payloads
> > > > > > > > > - If a payload has a different allocation then it
> > > > > > > > > previously
> > > > > > > > > did,
> > > > > > > > > update the
> > > > > > > > > payload
> > > > > > > > > - If the payload is new, create it
> > > > > > > > > - If a payload no longer has an allocation, remove the
> > > > > > > > > payload
> > > > > > > > >
> > > > > > > > > At first glance this seems totally correct - but I'm not
> > > > > > > > > actually
> > > > > > > > > entirely
> > > > > > > > > convinced it is? Particularly because it seems like the order
> > > > > > > > > in
> > > > > > > > > which
> > > > > > > > > we do creation/deletion of payloads is totally arbitrary. To
> > > > > > > > > explain
> > > > > > > > > what
> > > > > > > > > I mean by that, consider a state transition like this:
> > > > > > > > >
> > > > > > > > > vcpi_slots=15 vcpi_slots=35 vcpi_slots=14
> > > > > > > > > > 1 | 2 |xxxxxxxx|
> > > > > > > > >
> > > > > > > > > Let's say we want to increase payload #1 from 15 to 50, and
> > > > > > > > > disable
> > > > > > > > > payload #2 in the same atomic commit on DRM's side. If the
> > > > > > > > > order
> > > > > > > > > we
> > > > > > > > > update payloads is entirely arbitrary, we could end up doing
> > > > > > > > > this:
> > > > > > > > >
> > > > > > > > > * Increase VCPI slots payload #1 from 15->50 (total VCPI
> > > > > > > > > slots=99,
> > > > > > > > > overflow!)
> > > > > > > > > * Decrease VCPI slots payload #2 from 35->0 (total VCPI
> > > > > > > > > slots=50)
> > > > > > > > >
> > > > > > > > > Notice on the first step, we've technically overflowed the
> > > > > > > > > available
> > > > > > > > > number of VCPI slots in the payload table. This is still
> > > > > > > > > before
> > > > > > > > > step
> > > > > > > > > 2
> > > > > > > > > though, and I could be totally wrong here - perhaps this is
> > > > > > > > > entirely
> > > > > > > > > OK in
> > > > > > > > > the real world, and we're allowed to overflow VC slots as long
> > > > > > > > > as
> > > > > > > >
> > > > > > > > I think it's forbidden to allocate time slots beyond 64 when
> > > > > > > > we're
> > > > > > > > updating
> > > > > > > > payload ID table of the branch in the real world. Branch
> > > > > > > > probably
> > > > > > > > will NACK the DPCD write.
> > > > > > > >
> > > > > > > > > we repair the issue before step 2. But so far I can't seem to
> > > > > > > > > find
> > > > > > > > > anything in the DP 2.0 spec that explicitly states this would
> > > > > > > > > be
> > > > > > > > > OK
> > > > > > > > > -
> > > > > > > > > which
> > > > > > > > > makes me think we might fail some payload allocations if we
> > > > > > > > > don't
> > > > > > > > > always
> > > > > > > > > ensure we avoid overflows in between VC payload table changes
> > > > > > > >
> > > > > > > > Agree.
> > > > > > > > For amdgpu, I think we always do deallocation (call hws-
> > > > > > > > > funcs.reset_hw_ctx_wrap()) before allocation
> > > > > > > > (apply_single_controller_ctx_to_hw()).
> > > > > > > >
> > > > > > > > > Note that avoiding overflows would be as simple as just making
> > > > > > > > > sure
> > > > > > > > > we
> > > > > > > > > send all VC payload table changes that free VC slots before
> > > > > > > > > sending
> > > > > > > > > any that take new slots.
> > > > > > > > >
> > > > > > > > > Again - I haven't actually confirmed this yet and am hoping to
> > > > > > > > > test
> > > > > > > > > stuff
> > > > > > > > > like this very soon as I'm pretty close finishing up the
> > > > > > > > > initial
> > > > > > > > > attempt
> > > > > > > > > at removing the non-atomic MST code in the DRM helpers now. If
> > > > > > > > > my
> > > > > > > > > theory
> > > > > > > > > ends up being correct here, I can fix this in my rewrite of
> > > > > > > > > the
> > > > > > > > > MST payload management code. But I figured it might be worth
> > > > > > > > > mentioning in
> > > > > > > > > the mean time in case you think it might be relevant to the
> > > > > > > > > problem here :).
> > > > > > > > >
> > > > > > > > > On Wed, 2022-01-12 at 16:47 -0500, Lyude Paul wrote:
> > > > > > > > > > (CC'ing this to dri-devel, since this is basically patch
> > > > > > > > > > review)
> > > > > > > > > >
> > > > > > > > > > Alright - so first off sorry about the broken debugging
> > > > > > > > > > patch! I
> > > > > > > > > > thought I had tested that but I guess I hadn't tested it
> > > > > > > > > > well
> > > > > > > > > > enough,
> > > > > > > > > > I'll get it fixed asap, but feel free to try getting to it
> > > > > > > > > > before
> > > > > > > > > > I
> > > > > > > > > > do.
> > > > > > > > > >
> > > > > > > > > > As for this patch... (comments below)
> > > > > > > > > >
> > > > > > > > > > On Mon, 2021-12-20 at 02:17 +0000, Lin, Wayne wrote:
> > > > > > > > > > > [AMD Official Use Only]
> > > > > > > > > > >
> > > > > > > > > > > Hi Lyude,
> > > > > > > > > > >
> > > > > > > > > > > No rush and thanks for your time! : ) Just want to help
> > > > > > > > > > > clarify
> > > > > > > > > > > what
> > > > > > > > > > > I mean that "registering a callback function"
> > > > > > > > > > > for CSN of disconnecting
> > > > > > > > > > > stream sink device (not mst branch case). Attach below the
> > > > > > > > > > > tentative
> > > > > > > > > > > patch that I planned to do. Thanks so much!
> > > > > > > > > > >
> > > > > > > > > > > Regards,
> > > > > > > > > > > Wayne
> > > > > > > > > > > ---
> > > > > > > > > > > .../display/amdgpu_dm/amdgpu_dm_mst_types.c | 53
> > > > > > > > > > > +++++++++++++++++++
> > > > > > > > > > > drivers/gpu/drm/drm_dp_mst_topology.c | 16 +++++-
> > > > > > > > > > > include/drm/drm_dp_mst_helper.h | 1 +
> > > > > > > > > > > 3 files changed, 68 insertions(+), 2 deletions(-)
> > > > > > > > > > >
> > > > > > > > > > > diff --git
> > > > > > > > > > > a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_type
> > > > > > > > > > > s.c
> > > > > > > > > > > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_type
> > > > > > > > > > > s.c
> > > > > > > > > > > index cc34a35d0bcb..d7343c64908c 100644
> > > > > > > > > > > ---
> > > > > > > > > > > a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_type
> > > > > > > > > > > s.c
> > > > > > > > > > > +++
> > > > > > > > > > > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_type
> > > > > > > > > > > s.c
> > > > > > > > > > > @@ -472,8 +472,61 @@ dm_dp_add_mst_connector(struct
> > > > > > > > > > > drm_dp_mst_topology_mgr *mgr,
> > > > > > > > > > > return connector;
> > > > > > > > > > > }
> > > > > > > > > > >
> > > > > > > > > > > +void dm_dp_notify_csn_disconnection(struct drm_connector
> > > > > > > > > > > +*connector) {
> > > > > > > > > > > + struct amdgpu_dm_connector *aconnector =
> > > > > > > > > > > + to_amdgpu_dm_connector(connector);
> > > > > > > > > > > + struct dc_sink *dc_sink = aconnector->dc_sink;
> > > > > > > > > > > + struct dc_link *dc_link = aconnector->dc_link;
> > > > > > > > > > > + struct amdgpu_device *adev = drm_to_adev(ddev);
> > > > > > > > > > > +
> > > > > > > > > > > + ASSERT(dc_link);
> > > > > > > > > > > +
> > > > > > > > > > > + if (dc_sink) {
> > > > > > > > > > > + mutex_lock(&adev->dm.dc_lock);
> > > > > > > > > > > +
> > > > > > > > > > > + /*clear the remote sink of the link*/
> > > > > > > > > > > + dc_link_remove_remote_sink(dc_link,
> > > > > > > > > > > dc_sink);
> > > > > > > > > > > + dc_sink_release(dc_sink);
> > > > > > > > > > > + aconnector->dc_sink = NULL;
> > > > > > > > > > > +
> > > > > > > > > > > + mutex_unlock(&adev->dm.dc_lock);
> > > > > > > > > > > + }
> > > > > > > > > > > +}
> > > > > > > > > > > +
> > > > > > > > > > > static const struct drm_dp_mst_topology_cbs dm_mst_cbs =
> > > > > > > > > > > {
> > > > > > > > > > > .add_connector = dm_dp_add_mst_connector,
> > > > > > > > > > > + .notify_csn_disconnection =
> > > > > > > > > > > dm_dp_notify_csn_disconnection,
> > > > > > > > > > > };
> > > > > > > > > >
> > > > > > > > > > I still don't really think this is a good idea. This seems
> > > > > > > > > > like
> > > > > > > > > > it's
> > > > > > > > > > just adding another hotplugging path to the code in order to
> > > > > > > > > > avoid
> > > > > > > > > > sending hotplugs for non-endpoint devices. In addition to
> > > > > > > > > > the
> > > > > > > >
> > > > > > > > So, what I wanted to do is to add a callback function for
> > > > > > > > endpoint
> > > > > > > > devices
> > > > > > > > case as described above. For disconnection of non-endpoint
> > > > > > > > devices
> > > > > > > > is
> > > > > > > > already taken care by current code.
> > > > > > > >
> > > > > > > > > > drm_connector issues I mentioned before, we also really need
> > > > > > > > > > to
> > > > > > > > > > stop
> > > > > > > > > > doing any kind of payload maintence in hotplugging paths.
> > > > > > > > > > The
> > > > > > > > > > reality
> > > > > > > > > > is any kind of payload maintanence we do outside of normal
> > > > > > > > > > modesetting
> > > > > > > > > > paths is a relic from legacy modesetting that I'm dropping
> > > > > > > > > > ASAP
> > > > > > > > > > (more
> > > > > > > > > > on this below), and we can't keep adding to it because it
> > > > > > > > > > dramatically
> > > > > > > > > > complicates maintanence as well.
> > > > > > > >
> > > > > > > > > >
> > > > > > > > > > Sorry for repeating this point so often but - the biggest
> > > > > > > > > > issue
> > > > > > > > > > too
> > > > > > > > > > is
> > > > > > > > > > I'm still not sure what it is we're even avoiding here. We
> > > > > > > > > > know
> > > > > > > > > > resources aren't released consistently, and that we're able
> > > > > > > > > > to
> > > > > > > > > > reproduce the behavior with repeated hotplugs. We also know
> > > > > > > > > > that
> > > > > > > > > > if
> > > > > > > > > > we
> > > > > > > > > > skip sending certain hotplug events, that fixes the issue.
> > > > > > > > > > And
> > > > > > > > > > we
> > > > > > > > > > know
> > > > > > > > > > we can workaround it by adding a special case for forcing a
> > > > > > > > > > payload
> > > > > > > > > > release in DC. But none of those actually tell us exactly
> > > > > > > > > > what
> > > > > > > > > > piece
> > > > > > > > > > of code is leaking and why, which means that any workarounds
> > > > > > > > > > we're
> > > > > > > > > > putting in to avoid this mysterious guilty section of code
> > > > > > > > > > we
> > > > > > > > > > don't
> > > > > > > > > > entirely understand either - which means we're just adding
> > > > > > > > > > more
> > > > > > > > > > code
> > > > > > > > > > in that no one actually fully understands. This just ends up
> > > > > > > > > > making
> > > > > > > > > > maintence difficult because every change in code nearby
> > > > > > > > > > workarounds
> > > > > > > > > > like this has to strugle to try to figure out said
> > > > > > > > > > workarounds
> > > > > > > > > > in
> > > > > > > > > > order to avoid breaking things.
> > > > > > > >
> > > > > > > > Thank you Lyude for the reminder and I totally agree with you by
> > > > > > > > avoiding
> > > > > > > > adding workaround since it will get the code maintenance harder.
> > > > > > > > And
> > > > > > > > I
> > > > > > > > think the root cause of the issue that I observed before is
> > > > > > > > quite
> > > > > > > > concrete.
> > > > > > > > There is no code path for us to release dc_sink under the unplug
> > > > > > > > scenario
> > > > > > > > that I described above.
> > > > > > > >
> > > > > > > > > >
> > > > > > > > > > I'm actually currently running into these "later" issues
> > > > > > > > > > right
> > > > > > > > > > now,
> > > > > > > > > > as
> > > > > > > > > > recently I've (-actively-, finally!!!) been working on
> > > > > > > > > > trying to
> > > > > > > > > > remove as much non-atomic MST as I can because. As it turns
> > > > > > > > > > out
> > > > > > > > > > -
> > > > > > > > > > a
> > > > > > > > > > huge amount of the payload maintanence code just isn't
> > > > > > > > > > needed at
> > > > > > > > > > all
> > > > > > > > > > when we stop caring about non-atomic drivers and stick
> > > > > > > > > > everything
> > > > > > > > > > in
> > > > > > > > > > atomic state structs. Step 1 for updating updating the
> > > > > > > > > > payload
> > > > > > > > > > table,
> > > > > > > > > > e.g. drm_dp_update_payload_part1(), is a great example of
> > > > > > > > > > how
> > > > > > > > > > messy
> > > > > > > > > > things have become. Here's a small sample of some of the
> > > > > > > > > > stuff
> > > > > > > > > > I've
> > > > > > > > > > seen from just that one function so far that either just
> > > > > > > > > > don't
> > > > > > > > > > make
> > > > > > > > > > sense here or is totally redundant. I should note that a lot
> > > > > > > > > > of
> > > > > > > > > > these
> > > > > > > > > > things also come from patches I reviwed, but didn't really
> > > > > > > > > > look
> > > > > > > > > > at
> > > > > > > > > > as
> > > > > > > > > > closely as I should have because I was swamped at work, some
> > > > > > > > > > are
> > > > > > > > > > historical artifacts, and others are less-than-ideal patches
> > > > > > > > > > I
> > > > > > > > > > got
> > > > > > > > > > wrote myself when I was first started working on MST and
> > > > > > > > > > didn't
> > > > > > > > > > know
> > > > > > > > > > the code as well as I do
> > > > > > > > > > now:
> > > > > > > > > >
> > > > > > > > > > * We try to avoid some sort of userspace issue by using
> > > > > > > > > > drm_dp_mst_port_downstream_of_branch() to avoid releasing
> > > > > > > > > > payloads
> > > > > > > > > > for a
> > > > > > > > > > branch if we can't prove it's downstream of the top of
> > > > > > > > > > the
> > > > > > > > > > topology. This
> > > > > > > > > > seems to workaround either a userspace bug. This is a
> > > > > > > > > > redundant,
> > > > > > > > > > since
> > > > > > > > > > that's what topology refs are already supposed to be
> > > > > > > > > > doing to
> > > > > > > > > > the
> > > > > > > > > > extent is
> > > > > > > > > > reasonably possibly. It's also unfortunately racy
> > > > > > > > > > solution
> > > > > > > > > > because
> > > > > > > > > > we have
> > > > > > > > > > to be able to handle the situation where a connector is
> > > > > > > > > > removed
> > > > > > > > > > from under
> > > > > > > > > > us. That can happen at any time, including _immediately_
> > > > > > > > > > after
> > > > > > > > > > we
> > > > > > > > > > call
> > > > > > > > > > drm_dp_mst_port_downstream_of_branch() - rendering the
> > > > > > > > > > call
> > > > > > > > > > not
> > > > > > > > > > really
> > > > > > > > > > useful.
> > > > > > > > > > * If we fail to validate the sink in
> > > > > > > > > > drm_dp_update_payload_part,
> > > > > > > > > > we
> > > > > > > > > > don't
> > > > > > > > > > update the payload table. I think at best this solution
> > > > > > > > > > is
> > > > > > > > > > racy
> > > > > > > > > > and
> > > > > > > > > > not
> > > > > > > > > > useful, at worst it leaves us with a payload table that
> > > > > > > > > > doesn't
> > > > > > > > > > match what
> > > > > > > > > > we attempted to set in the atomic state - which at worst
> > > > > > > > > > brings
> > > > > > > > > > us
> > > > > > > > > > into
> > > > > > > > > > undefined territory where we're just plain out of sync
> > > > > > > > > > with
> > > > > > > > > > the
> > > > > > > > > > reality in
> > > > > > > > > > hw.
> > > > > > > > > > * Actually fun fact - mgr->payloads and mgr->proposed_vcpis
> > > > > > > > > > both
> > > > > > > > > > can
> > > > > > > > > > and
> > > > > > > > > > definitely should be removed entirely. All of the info
> > > > > > > > > > for
> > > > > > > > > > mgr->payloads
> > > > > > > > > > could just be in the atomic state, because that + the
> > > > > > > > > > magic
> > > > > > > > > > of
> > > > > > > > > > atomic state
> > > > > > > > > > duplication means we'll also have an accurate view of the
> > > > > > > > > > previous
> > > > > > > > > > state's
> > > > > > > > > > payload allocations: which renders mgr->proposed_vcpis
> > > > > > > > > > redundant.
> > > > > > > > > >
> > > > > > > > > > Apologies for the long explanation again, but I hope that
> > > > > > > > > > explains
> > > > > > > > > > my
> > > > > > > >
> > > > > > > > Really really thanks for your kindly help on this : )
> > > > > > > > I'll try my best to get to your WIP branch soon. Thank you
> > > > > > > > Lyude!
> > > > > > > >
> > > > > > > > > > point here a bit. I'm going to be trying to get to moving
> > > > > > > > > > amdgpu's
> > > > > > > > > > DSC
> > > > > > > > > > code out of amdgpu and into DRM helpers as well soon, so I'm
> > > > > > > > > > really
> > > > > > > > > > determined to clean stuff up beforehand as every time I've
> > > > > > > > > > done
> > > > > > > > > > so
> > > > > > > > > > it's become substantially easier to make changes to this
> > > > > > > > > > code.
> > > > > > > > > > Things
> > > > > > > > > > used to be even worse before I started cleaning things up 2
> > > > > > > > > > or 3
> > > > > > > > > > years
> > > > > > > > > > ago, where simple changes would end up getting me stuck
> > > > > > > > > > spending
> > > > > > > > > > hours
> > > > > > > > > > trying to dig through lockdep or memory manegement issues.
> > > > > > > > > > As
> > > > > > > > > > well,
> > > > > > > > > > I
> > > > > > > > > > would be entirely unsurprised if bugs like this very payload
> > > > > > > > > > leak
> > > > > > > > > > we're working on just disappear once we've gotten rid of all
> > > > > > > > > > the
> > > > > > > > > > extraneous workarounds and state tracking here - especially
> > > > > > > > > > with
> > > > > > > > > > how
> > > > > > > > > > many special cases we have for maintaining the payload table
> > > > > > > > > > right
> > > > > > > > > > now. That's certainly ended up being the case in the past
> > > > > > > > > > with a
> > > > > > > > > > number of other difficult to track down issues I've dealt
> > > > > > > > > > with
> > > > > > > > > > in
> > > > > > > > > > MST.
> > > > > > > > > >
> > > > > > > > > > Anyhow. I've been way more productive this year then last
> > > > > > > > > > because
> > > > > > > > > > I
> > > > > > > > > > had over a month off work and am finally not super burnt out
> > > > > > > > > > from
> > > > > > > > > > my
> > > > > > > > > > job, and so far I've been making progress on the payload
> > > > > > > > > > state
> > > > > > > > > > cleanup
> > > > > > > > > > far faster then I was last year :). I think if you can't
> > > > > > > > > > figure
> > > > > > > > > > out
> > > > > > > > > > where the leak is coming from even once I get the debugging
> > > > > > > > > > patches
> > > > > > > > > > I
> > > > > > > > > > mentioned fixed up, it might be a good idea for us to try
> > > > > > > > > > again
> > > > > > > > > > after
> > > > > > > > > > I've got some of this code cleaned up. I've got a currently
> > > > > > > > > > WIP
> > > > > > > > > > branch
> > > > > > > > > > here:
> > > > > > > > > >
> > > > > > > > > > https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitl
> > > > > > > > > > ab.freedesktop.org%2Flyudess%2Flinux%2F-
> > > > > > > > > > %2Fcommit%2F624dd68fa804e64b5b
> > > > > > > > > > 2060e4735d7317090692b5&data=04%7C01%7Cwayne.lin%40amd.co
> > > > > > > > > > m%7C
> > > > > > > > > > d4
> > > > > > > > > > bd
> > > > > > > > > > c7
> > > > > > > > > > 59eb274bfccc8208d9daef41fe%7C3dd8961fe4884e608e11a82d994e183
> > > > > > > > > > d%7C
> > > > > > > > > > 0%
> > > > > > > > > > 7C
> > > > > > > > > > 0%
> > > > > > > > > > 7C637781543416430632%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjA
> > > > > > > > > > wMDA
> > > > > > > > > > iL
> > > > > > > > > > CJ
> > > > > > > > > > QI
> > > > > > > > > > joiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=n
> > > > > > > > > > FpVl
> > > > > > > > > > %2
> > > > > > > > > > BV
> > > > > > > > > > oF
> > > > > > > > > > 40JPabfRMcR6Cz7ZHDwt%2BBpLDBNdXftJaA%3D&reserved=0
> > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > void amdgpu_dm_initialize_dp_connector(struct
> > > > > > > > > > > amdgpu_display_manager *dm, diff --git
> > > > > > > > > > > a/drivers/gpu/drm/drm_dp_mst_topology.c
> > > > > > > > > > > b/drivers/gpu/drm/drm_dp_mst_topology.c
> > > > > > > > > > > index 857c5d15e81d..a70e26c5d084 100644
> > > > > > > > > > > --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> > > > > > > > > > > +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> > > > > > > > > > > @@ -2508,6 +2508,7 @@ drm_dp_mst_handle_conn_stat(struct
> > > > > > > > > > > drm_dp_mst_branch *mstb,
> > > > > > > > > > > u8 new_pdt;
> > > > > > > > > > > bool new_mcs;
> > > > > > > > > > > bool dowork = false, create_connector = false;
> > > > > > > > > > > + bool notify_unplug_event = false;
> > > > > > > > > > >
> > > > > > > > > > > port = drm_dp_get_port(mstb, conn_stat-
> > > > > > > > > > > >port_number);
> > > > > > > > > > > if (!port)
> > > > > > > > > > > @@ -2520,6 +2521,9 @@ drm_dp_mst_handle_conn_stat(struct
> > > > > > > > > > > drm_dp_mst_branch *mstb,
> > > > > > > > > > > * port, so just throw the port
> > > > > > > > > > > out
> > > > > > > > > > > and
> > > > > > > > > > > make
> > > > > > > > > > > sure we
> > > > > > > > > > > * reprobe the link address of
> > > > > > > > > > > it's
> > > > > > > > > > > parent
> > > > > > > > > > > MSTB
> > > > > > > > > > > */
> > > > > > > > > > > + /* should also consider
> > > > > > > > > > > notify_unplug_event
> > > > > > > > > > > here.
> > > > > > > > > > > + * but it's not a normal case for
> > > > > > > > > > > products
> > > > > > > > > > > +in the
> > > > > > > > > > > market
> > > > > > > > > > > + */
> > > > > > > > > > >
> > > > > > > > > > > drm_dp_mst_topology_unlink_port(mgr,
> > > > > > > > > > > port);
> > > > > > > > > > > mstb->link_address_sent = false;
> > > > > > > > > > > dowork = true; @@ -2541,10
> > > > > > > > > > > +2545,14 @@
> > > > > > > > > > > drm_dp_mst_handle_conn_stat(struct
> > > > > > > > > > > drm_dp_mst_branch
> > > > > > > > > > > *mstb,
> > > > > > > > > > > port->ddps = conn_stat-
> > > > > > > > > > > > displayport_device_plug_status;
> > > > > > > > > > >
> > > > > > > > > > > if (old_ddps != port->ddps) {
> > > > > > > > > > > - if (port->ddps && !port->input)
> > > > > > > > > > > + if (port->ddps && !port->input) {
> > > > > > > > > > >
> > > > > > > > > > > drm_dp_send_enum_path_resources(mgr,
> > > > > > > > > > > mstb,
> > > > > > > > > > > port);
> > > > > > > > > > > - else
> > > > > > > > > > > + } else {
> > > > > > > > > > > port->full_pbn = 0;
> > > > > > > > > > > + if (port->connector &&
> > > > > > > > > > > +
> > > > > > > > > > > drm_dp_mst_is_end_device(port-
> > > > > > > > > > > > pdt,
> > > > > > > > > > > +port-
> > > > > > > > > > > > mcs))
> > > > > > > > > > > + notify_unplug_event =
> > > > > > > > > > > true;
> > > > > > > > > > > + }
> > > > > > > > > > > }
> > > > > > > > > > >
> > > > > > > > > > > new_pdt = port->input ? DP_PEER_DEVICE_NONE :
> > > > > > > > > > > conn_stat-
> > > > > > > > > > > > peer_device_type;
> > > > > > > > > > > @@ -2557,11 +2565,15 @@ drm_dp_mst_handle_conn_stat(struct
> > > > > > > > > > > drm_dp_mst_branch
> > > > > > > > > > > *mstb,
> > > > > > > > > > > dowork = false;
> > > > > > > > > > > }
> > > > > > > > > > >
> > > > > > > > > > > + if (notify_unplug_event &&
> > > > > > > > > > > +mgr->cbs->notify_csn_disconnection)
> > > > > > > > > > > + mgr->cbs->notify_csn_disconnection(port-
> > > > > > > > > > > > connector);
> > > > > > > > > > > +
> > > > > > > > > > > if (port->connector)
> > > > > > > > > > > drm_modeset_unlock(&mgr->base.lock);
> > > > > > > > > > > else if (create_connector)
> > > > > > > > > > > drm_dp_mst_port_add_connector(mstb, port);
> > > > > > > > > > >
> > > > > > > > > > > +
> > > > > > > > > > > out:
> > > > > > > > > > > drm_dp_mst_topology_put_port(port);
> > > > > > > > > > > if (dowork)
> > > > > > > > > > > diff --git a/include/drm/drm_dp_mst_helper.h
> > > > > > > > > > > b/include/drm/drm_dp_mst_helper.h index
> > > > > > > > > > > 78044ac5b59b..ff9e47729841
> > > > > > > > > > > 100644
> > > > > > > > > > > --- a/include/drm/drm_dp_mst_helper.h
> > > > > > > > > > > +++ b/include/drm/drm_dp_mst_helper.h
> > > > > > > > > > > @@ -525,6 +525,7 @@ struct drm_dp_mst_topology_cbs {
> > > > > > > > > > > * IRQ pulse handler.
> > > > > > > > > > > */
> > > > > > > > > > > void (*poll_hpd_irq)(struct
> > > > > > > > > > > drm_dp_mst_topology_mgr
> > > > > > > > > > > *mgr);
> > > > > > > > > > > + void (*notify_csn_disconnection)(struct
> > > > > > > > > > > drm_connector
> > > > > > > > > > > +*connector);
> > > > > > > > > > > };
> > > > > > > > > > >
> > > > > > > > > > > #define DP_MAX_PAYLOAD (sizeof(unsigned long) * 8)
> > > > > > > > > > > --
> > > > > > > > > > > 2.31.0
> > > > > > > > > > >
> > > > > > > > > > > > -----Original Message-----
> > > > > > > > > > > > From: Lin, Wayne
> > > > > > > > > > > > Sent: Wednesday, December 8, 2021 11:39 AM
> > > > > > > > > > > > To: 'Lyude Paul' <lyude at redhat.com>
> > > > > > > > > > > > Subject: RE: [PATCH] WIP: drm/dp_mst: Add support for
> > > > > > > > > > > > dumping
> > > > > > > > > > > > topology ref histories from debugfs
> > > > > > > > > > > >
> > > > > > > > > > > > No worries Lyude!
> > > > > > > > > > > > Thanks for keeping helping on this. Take your time : )
> > > > > > > > > > > >
> > > > > > > > > > > > > -----Original Message-----
> > > > > > > > > > > > > From: Lyude Paul <lyude at redhat.com>
> > > > > > > > > > > > > Sent: Wednesday, December 8, 2021 7:05 AM
> > > > > > > > > > > > > To: Lin, Wayne <Wayne.Lin at amd.com>
> > > > > > > > > > > > > Subject: Re: [PATCH] WIP: drm/dp_mst: Add support for
> > > > > > > > > > > > > dumping
> > > > > > > > > > > > > topology ref histories from debugfs
> > > > > > > > > > > > >
> > > > > > > > > > > > > Sorry! I will try to get to this tomorrow, if not then
> > > > > > > > > > > > > sometime
> > > > > > > > > > > > > this week.
> > > > > > > > > > > > >
> > > > > > > > > > > > > On Tue, 2021-11-30 at 08:41 +0000, Lin, Wayne wrote:
> > > > > > > > > > > > > > [Public]
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > Hi Lyude,
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > Finally have some bandwidth to get back to this
> > > > > > > > > > > > > > problem!
> > > > > > > > > > > > > > I roughly went through this patch and I'm just aware
> > > > > > > > > > > > > > that
> > > > > > > > > > > > > > we
> > > > > > > > > > > > > > already have such kind of convenient tool for a
> > > > > > > > > > > > > > while.
> > > > > > > > > > > > > > I think it's definitely useful for us to track
> > > > > > > > > > > > > > port/mstb
> > > > > > > > > > > > > > reference count issues and I'll start to embrace
> > > > > > > > > > > > > > this
> > > > > > > > > > > > > > feature
> > > > > > > > > > > > > > for cleaning up those issues. Thank you Lyude!
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > However, I think the issue that I was trying to fix
> > > > > > > > > > > > > > is
> > > > > > > > > > > > > > not
> > > > > > > > > > > > > > related to what you suggested:
> > > > > > > > > > > > > > " The idea here is that if stream resources aren't
> > > > > > > > > > > > > > being
> > > > > > > > > > > > > > released, my guess would be that we're not dropping
> > > > > > > > > > > > > > topology
> > > > > > > > > > > > > > references for the port which means the connector
> > > > > > > > > > > > > > never
> > > > > > > > > > > > > > goes
> > > > > > > > > > > > > > away."
> > > > > > > > > > > > > > The issue I was trying to fix is about releasing
> > > > > > > > > > > > > > dc_link->remote_sinks while receiving a CSN message
> > > > > > > > > > > > > > notifying
> > > > > > > > > > > > > > the connection status of a sst connector of a port
> > > > > > > > > > > > > > changed
> > > > > > > > > > > > > > from connected to disconnected. Not the connection
> > > > > > > > > > > > > > status
> > > > > > > > > > > > > > changed of a mst branch device.
> > > > > > > > > > > > > > e.g.
> > > > > > > > > > > > > > src - 1st_mstb - 2nd_mstb - sst_monitor => src -
> > > > > > > > > > > > > > 1st_mstb
> > > > > > > > > > > > > > (disconnect) 2nd_mstb - sst_monitor
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > In above case, after receiving CSN, we will put
> > > > > > > > > > > > > > topology
> > > > > > > > > > > > > > references of 2nd mstb and its port which is
> > > > > > > > > > > > > > connected
> > > > > > > > > > > > > > with
> > > > > > > > > > > > > > the sst monitor. As the result of that, we can call
> > > > > > > > > > > > > > drm_dp_delayed_destroy_port() to unregister and put
> > > > > > > > > > > > > > the
> > > > > > > > > > > > > > drm
> > > > > > > > > > > > > > connector.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > However, in below case:
> > > > > > > > > > > > > > e.g.
> > > > > > > > > > > > > > src - 1st_mstb - sst_monitor => src - 1st_mstb
> > > > > > > > > > > > > > (disconnect)
> > > > > > > > > > > > > > sst_monitor
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > In this case, which is the case having problem, it
> > > > > > > > > > > > > > definitely
> > > > > > > > > > > > > > won't decrease the topology references count of the
> > > > > > > > > > > > > > port
> > > > > > > > > > > > > > which
> > > > > > > > > > > > > > was connected to the sst monitor to zero since the
> > > > > > > > > > > > > > port
> > > > > > > > > > > > > > is
> > > > > > > > > > > > > > still existing in the topology. Same as the malloc
> > > > > > > > > > > > > > reference
> > > > > > > > > > > > > > since the port can't get destroyed. Hence, the port
> > > > > > > > > > > > > > still
> > > > > > > > > > > > > > exists and we won't call
> > > > > > > > > > > > > > drm_dp_delayed_destroy_port() to unregister and put
> > > > > > > > > > > > > > the
> > > > > > > > > > > > > > drm
> > > > > > > > > > > > > > connector.
> > > > > > > > > > > > > > I looked up the code and
> > > > > > > > > > > > > > drm_dp_delayed_destroy_port()
> > > > > > > > > > > > > > seems
> > > > > > > > > > > > > > like the only place to call drm_connector_put()
> > > > > > > > > > > > > > which
> > > > > > > > > > > > > > means
> > > > > > > > > > > > > > we
> > > > > > > > > > > > > > can't put reference count of drm connector under
> > > > > > > > > > > > > > this
> > > > > > > > > > > > > > case
> > > > > > > > > > > > > > and
> > > > > > > > > > > > > > can't release dc_sink resource by destroying drm
> > > > > > > > > > > > > > connector.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > I would also like to point out that this resource
> > > > > > > > > > > > > > (remote_sinks) is specific to different stream
> > > > > > > > > > > > > > sinks. So
> > > > > > > > > > > > > > if
> > > > > > > > > > > > > > we're trying to release this dc_sink resource by
> > > > > > > > > > > > > > destroying
> > > > > > > > > > > > > > the drm connector, it conflicts the idea that you
> > > > > > > > > > > > > > suggested
> > > > > > > > > > > > > > before that we should always keep the drm connector
> > > > > > > > > > > > > > until
> > > > > > > > > > > > > > it's
> > > > > > > > > > > > > > no longer reachable in the topology.
> > > > > > > > > > > > > > Releasing dc_sink should be binding with the
> > > > > > > > > > > > > > disconnection
> > > > > > > > > > > > > > event.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > I understand your concern that we should not just
> > > > > > > > > > > > > > easily
> > > > > > > > > > > > > > change the logic here since it's the result after
> > > > > > > > > > > > > > solving
> > > > > > > > > > > > > > tons
> > > > > > > > > > > > > > of bugs before and might cause other side effect.
> > > > > > > > > > > > > > So,
> > > > > > > > > > > > > > just
> > > > > > > > > > > > > > my
> > > > > > > > > > > > > > 2 cents, what I'm thinking is to register a callback
> > > > > > > > > > > > > > function
> > > > > > > > > > > > > > for our driver to notify us that the remote sink is
> > > > > > > > > > > > > > detached.
> > > > > > > > > > > > > > This just aligns our flow handling long HPD event of
> > > > > > > > > > > > > > legacy
> > > > > > > > > > > > > > (sst) DP.
> > > > > > > > > > > > > > For sst case, once we detect long HPD event
> > > > > > > > > > > > > > indicating
> > > > > > > > > > > > > > the
> > > > > > > > > > > > > > monitor is detached, we will immediately try to
> > > > > > > > > > > > > > release
> > > > > > > > > > > > > > the
> > > > > > > > > > > > > > dc_link->local_sink and fire hotplug event to upper
> > > > > > > > > > > > > > layer.
> > > > > > > > > > > > > > Same as here, once receives a CSN message notifying
> > > > > > > > > > > > > > a
> > > > > > > > > > > > > > drm
> > > > > > > > > > > > > > connector is changed from connected to disconnected,
> > > > > > > > > > > > > > trigger
> > > > > > > > > > > > > > the callback function and we can try to release the
> > > > > > > > > > > > > > dc_sink
> > > > > > > > > > > > > > resource.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > Would like to know your thought and insight please :
> > > > > > > > > > > > > > )
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > Btw, I got some errors and warnings while building
> > > > > > > > > > > > > > and
> > > > > > > > > > > > > > have
> > > > > > > > > > > > > > some code adjustments as below : ) Thank you Lyude
> > > > > > > > > > > > > > for
> > > > > > > > > > > > > > your
> > > > > > > > > > > > > > always kindly help!!
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > Regards,
> > > > > > > > > > > > > > Wayne
> > > > > > > > > > > > > > > -----Original Message-----
> > > > > > > > > > > > > > > From: Lyude Paul <lyude at redhat.com>
> > > > > > > > > > > > > > > Sent: Wednesday, November 3, 2021 7:15 AM
> > > > > > > > > > > > > > > To: Lin, Wayne <Wayne.Lin at amd.com>
> > > > > > > > > > > > > > > Subject: [PATCH] WIP: drm/dp_mst: Add support for
> > > > > > > > > > > > > > > dumping
> > > > > > > > > > > > > > > topology ref histories from debugfs
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > TODO:
> > > > > > > > > > > > > > > * Implement support for i915
> > > > > > > > > > > > > > > * Finish writing this commit message
> > > > > > > > > > > > > > > * ???
> > > > > > > > > > > > > > > * profit
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > Signed-off-by: Lyude Paul <lyude at redhat.com>
> > > > > > > > > > > > > > > ---
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > Hey wayne! SO-hopefully if I did this correctly
> > > > > > > > > > > > > > > then
> > > > > > > > > > > > > > > this
> > > > > > > > > > > > > > > should just work on amdgpu. What this patch should
> > > > > > > > > > > > > > > do
> > > > > > > > > > > > > > > is
> > > > > > > > > > > > > > > add
> > > > > > > > > > > > > > > a debugfs file to amdgpu called
> > > > > > > > > > > > > > > "amdgpu_dp_mst_topology_refs", and when you read
> > > > > > > > > > > > > > > the
> > > > > > > > > > > > > > > file
> > > > > > > > > > > > > > > it
> > > > > > > > > > > > > > > should print out the topology reference history of
> > > > > > > > > > > > > > > every
> > > > > > > > > > > > > > > MSTB and Port in memory, along with how many times
> > > > > > > > > > > > > > > we've
> > > > > > > > > > > > > > > hit
> > > > > > > > > > > > > > > the codepath in each backtrace. An example:
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > Port DP-5 (0000000005c37748) topology ref history:
> > > > > > > > > > > > > > > 1 gets (last at 58.468973):
> > > > > > > > > > > > > > > drm_dp_send_link_address+0x6a5/0xa00
> > > > > > > > > > > > > > > [drm_kms_helper]
> > > > > > > > > > > > > > > drm_dp_check_and_send_link_address+0xad/0xd0
> > > > > > > > > > > > > > > [drm_kms_helper]
> > > > > > > > > > > > > > > drm_dp_mst_link_probe_work+0x14e/0x1a0
> > > > > > > > > > > > > > > [drm_kms_helper]
> > > > > > > > > > > > > > > process_one_work+0x1e3/0x390
> > > > > > > > > > > > > > > worker_thread+0x50/0x3a0
> > > > > > > > > > > > > > > kthread+0x124/0x150
> > > > > > > > > > > > > > > ret_from_fork+0x1f/0x30
> > > > > > > > > > > > > > > 1 puts (last at 58.469357):
> > > > > > > > > > > > > > > drm_dp_mst_topology_put_port+0x6a/0x210
> > > > > > > > > > > > > > > [drm_kms_helper]
> > > > > > > > > > > > > > > drm_dp_send_link_address+0x39e/0xa00
> > > > > > > > > > > > > > > [drm_kms_helper]
> > > > > > > > > > > > > > > drm_dp_check_and_send_link_address+0xad/0xd0
> > > > > > > > > > > > > > > [drm_kms_helper]
> > > > > > > > > > > > > > > drm_dp_mst_link_probe_work+0x14e/0x1a0
> > > > > > > > > > > > > > > [drm_kms_helper]
> > > > > > > > > > > > > > > process_one_work+0x1e3/0x390
> > > > > > > > > > > > > > > worker_thread+0x50/0x3a0
> > > > > > > > > > > > > > > kthread+0x124/0x150
> > > > > > > > > > > > > > > ret_from_fork+0x1f/0x30
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > The idea here is that if stream resources aren't
> > > > > > > > > > > > > > > being
> > > > > > > > > > > > > > > released, my guess would be that we're not
> > > > > > > > > > > > > > > dropping
> > > > > > > > > > > > > > > topology
> > > > > > > > > > > > > > > references for the port which means the connector
> > > > > > > > > > > > > > > never
> > > > > > > > > > > > > > > goes
> > > > > > > > > > > > > > > away. So, if that's really the case then once we
> > > > > > > > > > > > > > > unplug
> > > > > > > > > > > > > > > the
> > > > > > > > > > > > > > > offending connector we should be able to find a
> > > > > > > > > > > > > > > pair
> > > > > > > > > > > > > > > of
> > > > > > > > > > > > > > > gets/puts for the offending leaked connector where
> > > > > > > > > > > > > > > the
> > > > > > > > > > > > > > > get/put count doesn't match up. Also, if the frame
> > > > > > > > > > > > > > > count
> > > > > > > > > > > > > > > on
> > > > > > > > > > > > > > > the backtrace isn't long enough you can increase
> > > > > > > > > > > > > > > the
> > > > > > > > > > > > > > > value
> > > > > > > > > > > > > > > of STACK_DEPTH in
> > > > > > > > > > > > > > > drivers/gpu/drm/drm_dp_mst_topology.c
> > > > > > > > > > > > > > > and
> > > > > > > > > > > > > > > recompile to get more frames.
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > To enable this, first enable CONFIG_EXPERT for
> > > > > > > > > > > > > > > your
> > > > > > > > > > > > > > > kernel
> > > > > > > > > > > > > > > which will unhide
> > > > > > > > > > > > > > > CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS.
> > > > > > > > > > > > > > > Then just enable
> > > > > > > > > > > > > > > CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS,
> > > > > > > > > > > > > > > recompile, and it should be good to go.
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > Let me know if this works for you, and hopefully
> > > > > > > > > > > > > > > this
> > > > > > > > > > > > > > > should
> > > > > > > > > > > > > > > tell us exactly what the problem actually is here.
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > .../amd/display/amdgpu_dm/amdgpu_dm_debugfs.c |
> > > > > > > > > > > > > > > 35
> > > > > > > > > > > > > > > ++++
> > > > > > > > > > > > > > > drivers/gpu/drm/drm_dp_mst_topology.c |
> > > > > > > > > > > > > > > 173
> > > > > > > > > > > > > > > ++++++++++++++----
> > > > > > > > > > > > > > > drivers/gpu/drm/nouveau/nouveau_debugfs.c |
> > > > > > > > > > > > > > > 35
> > > > > > > > > > > > > > > ++++
> > > > > > > > > > > > > > > include/drm/drm_dp_mst_helper.h |
> > > > > > > > > > > > > > > 18
> > > > > > > > > > > > > > > ++
> > > > > > > > > > > > > > > 4 files changed, 228 insertions(+), 33
> > > > > > > > > > > > > > > deletions(-)
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > diff --git
> > > > > > > > > > > > > > > a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_
> > > > > > > > > > > > > > > debu
> > > > > > > > > > > > > > > gf
> > > > > > > > > > > > > > > s.
> > > > > > > > > > > > > > > c
> > > > > > > > > > > > > > > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_
> > > > > > > > > > > > > > > debu
> > > > > > > > > > > > > > > gf
> > > > > > > > > > > > > > > s.
> > > > > > > > > > > > > > > c
> > > > > > > > > > > > > > > index 1a68a674913c..1a14732c52b4 100644
> > > > > > > > > > > > > > > ---
> > > > > > > > > > > > > > > a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_
> > > > > > > > > > > > > > > debu
> > > > > > > > > > > > > > > gf
> > > > > > > > > > > > > > > s.
> > > > > > > > > > > > > > > c
> > > > > > > > > > > > > > > +++
> > > > > > > > > > > > > > > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_
> > > > > > > > > > > > > > > debu
> > > > > > > > > > > > > > > gf
> > > > > > > > > > > > > > > +++ s.c
> > > > > > > > > > > > > > > @@ -3063,6 +3063,37 @@ static int
> > > > > > > > > > > > > > > mst_topo_show(struct
> > > > > > > > > > > > > > > seq_file *m, void
> > > > > > > > > > > > > > > *unused)
> > > > > > > > > > > > > > > return 0;
> > > > > > > > > > > > > > > }
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > +#ifdef CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS
> > > > > > > > > > > > > > > +static int mst_topology_ref_dump_show(struct
> > > > > > > > > > > > > > > seq_file
> > > > > > > > > > > > > > > *m,
> > > > > > > > > > > > > > > +void
> > > > > > > > > > > > > > > +*unused) {
> > > > > > > > > > > > > > > + struct amdgpu_device *adev = (struct
> > > > > > > > > > > > > > > amdgpu_device
> > > > > > > > > > > > > > > +*)m->private;
> > > > > > > > > > > > > > > + struct drm_device *dev = adev_to_drm(adev);
> > > > > > > > > > > > > > > + struct drm_connector *connector;
> > > > > > > > > > > > > > > + struct drm_connector_list_iter conn_iter;
> > > > > > > > > > > > > > > + struct amdgpu_dm_connector *aconnector;
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > + drm_connector_list_iter_begin(dev,
> > > > > > > > > > > > > > > &conn_iter);
> > > > > > > > > > > > > > > + drm_for_each_connector_iter(connector,
> > > > > > > > > > > > > > > &conn_iter)
> > > > > > > > > > > > > > > {
> > > > > > > > > > > > > > > + if (connector->connector_type !=
> > > > > > > > > > > > > > > DRM_MODE_CONNECTOR_DisplayPort)
> > > > > > > > > > > > > > > + continue;
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > + aconnector =
> > > > > > > > > > > > > > > +to_amdgpu_dm_connector(connector);
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > + /* Ensure we're only dumping the
> > > > > > > > > > > > > > > topology
> > > > > > > > > > > > > > > of
> > > > > > > > > > > > > > > a
> > > > > > > > > > > > > > > +root mst node
> > > > > > > > > > > > > > > */
> > > > > > > > > > > > > > > + if (!aconnector-
> > > > > > > > > > > > > > > >mst_mgr.max_payloads)
> > > > > > > > > > > > > > > + continue;
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > + seq_printf(m, "\nMST topology for
> > > > > > > > > > > > > > > connector
> > > > > > > > > > > > > > > +%d\n",
> > > > > > > > > > > > > > > aconnector->connector_id);
> > > > > > > > > > > > > > > + drm_dp_mst_dump_topology_refs(m,
> > > > > > > > > > > > > > > +&aconnector->mst_mgr);
> > > > > > > > > > > > > > > + }
> > > > > > > > > > > > > > > + drm_connector_list_iter_end(&conn_iter);
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > + return 0;
> > > > > > > > > > > > > > > +}
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > +DEFINE_SHOW_ATTRIBUTE(mst_topology_ref_dump);
> > > > > > > > > > > > > > > +#endif
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > /*
> > > > > > > > > > > > > > > * Sets trigger hpd for MST topologies.
> > > > > > > > > > > > > > > * All connected connectors will be rediscovered
> > > > > > > > > > > > > > > and
> > > > > > > > > > > > > > > re
> > > > > > > > > > > > > > > started as needed if val of 1 is sent.
> > > > > > > > > > > > > > > @@ -3299,6 +3330,10 @@ void
> > > > > > > > > > > > > > > dtn_debugfs_init(struct
> > > > > > > > > > > > > > > amdgpu_device
> > > > > > > > > > > > > > > *adev)
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > debugfs_create_file("amdgpu_mst_topology",
> > > > > > > > > > > > > > > 0444,
> > > > > > > > > > > > > > > root,
> > > > > > > > > > > > > > > adev, &mst_topo_fops);
> > > > > > > > > > > > > > > +#ifdef CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > debugfs_create_file("amdgpu_dp_mst_topology_refs",
> > > > > > > > > > > > > > > +0444, root, adev,
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > &mst_topology_ref_dump_fops);
> > > > > > > > > > > > > > > +#endif
> > > > > > > > > > > > > > > debugfs_create_file("amdgpu_dm_dtn_log",
> > > > > > > > > > > > > > > 0644,
> > > > > > > > > > > > > > > root,
> > > > > > > > > > > > > > > adev,
> > > > > > > > > > > > > > > &dtn_log_fops);
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
> > > > > > > > > > > > > > > b/drivers/gpu/drm/drm_dp_mst_topology.c
> > > > > > > > > > > > > > > index 1aa8702383d4..0159828c494d 100644
> > > > > > > > > > > > > > > --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> > > > > > > > > > > > > > > +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> > > > > > > > > > > > > > > @@ -1366,23 +1366,6 @@ static int
> > > > > > > > > > > > > > > drm_dp_mst_wait_tx_reply(struct drm_dp_mst_branch
> > > > > > > > > > > > > > > *mstb,
> > > > > > > > > > > > > > > return ret;
> > > > > > > > > > > > > > > }
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > -static struct drm_dp_mst_branch
> > > > > > > > > > > > > > > *drm_dp_add_mst_branch_device(u8 lct, u8
> > > > > > > > > > > > > > > *rad) -{
> > > > > > > > > > > > > > > - struct drm_dp_mst_branch *mstb;
> > > > > > > > > > > > > > > -
> > > > > > > > > > > > > > > - mstb = kzalloc(sizeof(*mstb), GFP_KERNEL);
> > > > > > > > > > > > > > > - if (!mstb)
> > > > > > > > > > > > > > > - return NULL;
> > > > > > > > > > > > > > > -
> > > > > > > > > > > > > > > - mstb->lct = lct;
> > > > > > > > > > > > > > > - if (lct > 1)
> > > > > > > > > > > > > > > - memcpy(mstb->rad, rad, lct / 2);
> > > > > > > > > > > > > > > - INIT_LIST_HEAD(&mstb->ports);
> > > > > > > > > > > > > > > - kref_init(&mstb->topology_kref);
> > > > > > > > > > > > > > > - kref_init(&mstb->malloc_kref);
> > > > > > > > > > > > > > > - return mstb;
> > > > > > > > > > > > > > > -}
> > > > > > > > > > > > > > > -
> > > > > > > > > > > > > > > static void drm_dp_free_mst_branch_device(struct
> > > > > > > > > > > > > > > kref
> > > > > > > > > > > > > > > *kref) {
> > > > > > > > > > > > > > > struct drm_dp_mst_branch *mstb = @@ -1642,12
> > > > > > > > > > > > > > > +1625,20
> > > > > > > > > > > > > > > @@ topology_ref_type_to_str(enum
> > > > > > > > > > > > > > > drm_dp_mst_topology_ref_type type)
> > > > > > > > > > > > > > > return "put";
> > > > > > > > > > > > > > > }
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > +static const char
> > > > > > > > > > > > > > > *topology_ref_history_type_to_str(enum
> > > > > > > > > > > > > > > +drm_dp_mst_topology_history_type type) {
> > > > > > > > > > > > > > > + if (type ==
> > > > > > > > > > > > > > > DRM_DP_MST_TOPOLOGY_HISTORY_PORT)
> > > > > > > > > > > > > > > + return "Port";
> > > > > > > > > > > > > > > + else
> > > > > > > > > > > > > > > + return "MSTB"; }
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > static void
> > > > > > > > > > > > > > > -__dump_topology_ref_history(struct
> > > > > > > > > > > > > > > drm_dp_mst_topology_ref_history *history,
> > > > > > > > > > > > > > > - void *ptr, const char
> > > > > > > > > > > > > > > *type_str)
> > > > > > > > > > > > > > > +dump_topology_ref_history(struct
> > > > > > > > > > > > > > > +drm_dp_mst_topology_ref_history *history, struct
> > > > > > > > > > > > > > > +drm_printer p)
> > > > > > > > > > > > > > > {
> > > > > > > > > > > > > > > - struct drm_printer p =
> > > > > > > > > > > > > > > drm_debug_printer(DBG_PREFIX);
> > > > > > > > > > > > > > > + char *connector_name = NULL;
> > > > > > > > > > > > > > > char *buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
> > > > > > > > > > > > > > > + void *ptr;
> > > > > > > > > > > > > > > int i;
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > if (!buf)
> > > > > > > > > > > > > > > @@ -1656,14 +1647,29 @@
> > > > > > > > > > > > > > > __dump_topology_ref_history(struct
> > > > > > > > > > > > > > > drm_dp_mst_topology_ref_history *history,
> > > > > > > > > > > > > > > if (!history->len)
> > > > > > > > > > > > > > > goto out;
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > + /* Get a pointer to the actual MSTB/port so
> > > > > > > > > > > > > > > we
> > > > > > > > > > > > > > > can
> > > > > > > > > > > > > > > the
> > > > > > > > > > > > > > > +memory
> > > > > > > > > > > > > > > address to the kernel log */
> > > > > > > > > > > > > > > + if (history->type ==
> > > > > > > > > > > > > > > DRM_DP_MST_TOPOLOGY_HISTORY_PORT)
> > > > > > > > > > > > > > > + ptr = container_of(history, struct
> > > > > > > > > > > > > > > +drm_dp_mst_port,
> > > > > > > > > > > > > > > topology_ref_history);
> > > > > > > > > > > > > > > + else
> > > > > > > > > > > > > > > + ptr = container_of(history, struct
> > > > > > > > > > > > > > > +drm_dp_mst_branch, topology_ref_history);
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > /* First, sort the list so that it goes from
> > > > > > > > > > > > > > > oldest
> > > > > > > > > > > > > > > to
> > > > > > > > > > > > > > > newest
> > > > > > > > > > > > > > > * reference entry
> > > > > > > > > > > > > > > */
> > > > > > > > > > > > > > > sort(history->entries, history->len,
> > > > > > > > > > > > > > > sizeof(*history->entries),
> > > > > > > > > > > > > > > topology_ref_history_cmp, NULL);
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > - drm_printf(&p, "%s (%p) topology count
> > > > > > > > > > > > > > > reached
> > > > > > > > > > > > > > > 0,
> > > > > > > > > > > > > > > dumping history:\n",
> > > > > > > > > > > > > > > - type_str, ptr);
> > > > > > > > > > > > > > > + if (history->type ==
> > > > > > > > > > > > > > > DRM_DP_MST_TOPOLOGY_HISTORY_PORT)
> > > > > > > > > > > > > > > +{
> > > > > > > > > > > > > > > + struct drm_dp_mst_port *port = ptr;
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > + if (port->connector)
> > > > > > > > > > > > > > > + connector_name =
> > > > > > > > > > > > > > > +port->connector->name;
> > > > > > > > > > > > > > > + }
> > > > > > > > > > > > > > > + if (connector_name)
> > > > > > > > > > > > > > > + drm_printf(&p, "Port %s (%p)
> > > > > > > > > > > > > > > topology
> > > > > > > > > > > > > > > ref
> > > > > > > > > > > > > > > +history:\n",
> > > > > > > > > > > > > > > connector_name, ptr);
> > > > > > > > > > > > > > > + else
> > > > > > > > > > > > > > > + drm_printf(&p, "%s (%p) topology ref
> > > > > > > > > > > > > > > +history:\n",
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > +topology_ref_history_type_to_str(history->type),
> > > > > > > > > > > > > > > ptr);
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > for (i = 0; i < history->len; i++) {
> > > > > > > > > > > > > > > const struct
> > > > > > > > > > > > > > > drm_dp_mst_topology_ref_entry
> > > > > > > > > > > > > > > *entry = @@
> > > > > > > > > > > > > > > -
> > > > > > > > > > > > > > > 1682,24 +1688,92 @@
> > > > > > > > > > > > > > > __dump_topology_ref_history(struct
> > > > > > > > > > > > > > > drm_dp_mst_topology_ref_history *history,
> > > > > > > > > > > > > > > ts_nsec, rem_nsec / 1000,
> > > > > > > > > > > > > > > buf);
> > > > > > > > > > > > > > > }
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > - /* Now free the history, since this is the
> > > > > > > > > > > > > > > only
> > > > > > > > > > > > > > > time
> > > > > > > > > > > > > > > we expose it */
> > > > > > > > > > > > > > > - kfree(history->entries);
> > > > > > > > > > > > > > > out:
> > > > > > > > > > > > > > > kfree(buf);
> > > > > > > > > > > > > > > }
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > +/**
> > > > > > > > > > > > > > > + * drm_dp_mst_dump_topology_refs - helper
> > > > > > > > > > > > > > > function
> > > > > > > > > > > > > > > for
> > > > > > > > > > > > > > > +dumping the topology ref history
> > > > > > > > > > > > > > > + * @m: File to print to
> > > > > > > > > > > > > > > + * @mgr: &struct drm_dp_mst_topology_mgr to use
> > > > > > > > > > > > > > > + *
> > > > > > > > > > > > > > > + * Prints the topology ref history of all ports
> > > > > > > > > > > > > > > and
> > > > > > > > > > > > > > > MSTBs
> > > > > > > > > > > > > > > +on @mgr that are still in memory,
> > > > > > > > > > > > > > > + * regardless of whether they're actually still
> > > > > > > > > > > > > > > reachable
> > > > > > > > > > > > > > > +through the topology or not. Only enabled
> > > > > > > > > > > > > > > + * when %CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS is
> > > > > > > > > > > > > > > enabled.
> > > > > > > > > > > > > > > +Can be implemented by drivers to assist
> > > > > > > > > > > > > > > + * with debugging leaks in the DP MST helpers.
> > > > > > > > > > > > > > > + */
> > > > > > > > > > > > > > > +void drm_dp_mst_dump_topology_refs(struct
> > > > > > > > > > > > > > > seq_file
> > > > > > > > > > > > > > > *m,
> > > > > > > > > > > > > > > +struct drm_dp_mst_topology_mgr *mgr) {
> > > > > > > > > > > > > > > + struct drm_dp_mst_topology_ref_history
> > > > > > > > > > > > > > > *history;
> > > > > > > > > > > > > > > + struct drm_printer p =
> > > > > > > > > > > > > > > drm_seq_file_printer(m);
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > + mutex_lock(&mgr->topology_ref_history_lock);
> > > > > > > > > > > > > > > + list_for_each_entry(history,
> > > > > > > > > > > > > > > +&mgr->topology_ref_history_list,
> > > > > > > > > > > > > > > +node)
> > > > > > > > > > > > > > > + dump_topology_ref_history(history,
> > > > > > > > > > > > > > > p);
> > > > > > > > > > > > > > > + mutex_unlock(&mgr-
> > > > > > > > > > > > > > > >topology_ref_history_lock);
> > > > > > > > > > > > > > > +}
> > > > > > > > > > > > > > > +EXPORT_SYMBOL(drm_dp_mst_dump_topology_refs);
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > +static void
> > > > > > > > > > > > > > > +__init_topology_ref_history(struct
> > > > > > > > > > > > > > > +drm_dp_mst_topology_ref_history
> > > > > > > > > > > > > > > *history,
> > > > > > > > > > > > > > > + struct
> > > > > > > > > > > > > > > drm_dp_mst_topology_mgr
> > > > > > > > > > > > > > > +*mgr,
> > > > > > > > > > > > > > > + enum
> > > > > > > > > > > > > > > +drm_dp_mst_topology_history_type
> > > > > > > > > > > > > > > +type) {
> > > > > > > > > > > > > > > + history->type = type;
> > > > > > > > > > > > > > > + INIT_LIST_HEAD(&history->node);
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > + mutex_lock(&mgr->topology_ref_history_lock);
> > > > > > > > > > > > > > > + list_add(&history->node,
> > > > > > > > > > > > > > > +&mgr->topology_ref_history_list);
> > > > > > > > > > > > > > > + mutex_unlock(&mgr-
> > > > > > > > > > > > > > > >topology_ref_history_lock);
> > > > > > > > > > > > > > > +}
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > +static void
> > > > > > > > > > > > > > > +__destroy_topology_ref_history(struct
> > > > > > > > > > > > > > > +drm_dp_mst_topology_ref_history
> > > > > > > > > > > > > > > *history,
> > > > > > > > > > > > > > > + struct
> > > > > > > > > > > > > > > drm_dp_mst_topology_mgr
> > > > > > > > > > > > > > > +*mgr) {
> > > > > > > > > > > > > > > + mutex_lock(&mgr->topology_ref_history_lock);
> > > > > > > > > > > > > > > + list_del(&mgr->topology_ref_history_list);
> > > > > > > > > > > > > > > + mutex_unlock(&mgr-
> > > > > > > > > > > > > > > >topology_ref_history_lock);
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > + kfree(history->entries); }
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > +static __always_inline void
> > > > > > > > > > > > > > > +init_port_topology_history(struct
> > > > > > > > > > > > > > > drm_dp_mst_topology_mgr
> > > > > > > > > > > > > > > +*mgr, struct drm_dp_mst_port *port) {
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > +__init_topology_ref_history(&port-
> > > > > > > > > > > > > > > > topology_ref_history,
> > > > > > > > > > > > > > > +mgr,
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > +DRM_DP_MST_TOPOLOGY_HISTORY_PORT);
> > > > > > > > > > > > > > > +}
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > +static __always_inline void
> > > > > > > > > > > > > > > +init_mstb_topology_history(struct
> > > > > > > > > > > > > > > drm_dp_mst_topology_mgr
> > > > > > > > > > > > > > > +*mgr, struct drm_dp_mst_branch *mstb) {
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > +__init_topology_ref_history(&mstb-
> > > > > > > > > > > > > > > > topology_ref_history,
> > > > > > > > > > > > > > > +mgr,
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > +DRM_DP_MST_TOPOLOGY_HISTORY_MSTB);
> > > > > > > > > > > > > > > +}
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > +static __always_inline void
> > > > > > > > > > > > > > > +destroy_port_topology_history(struct
> > > > > > > > > > > > > > > drm_dp_mst_port
> > > > > > > > > > > > > > > *port)
> > > > > > > > > > > > > > > +{
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > +__destroy_topology_ref_history(&port-
> > > > > > > > > > > > > > > > topology_ref_history,
> > > > > > > > > > > > > > > +port->mgr); }
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > +static __always_inline void
> > > > > > > > > > > > > > > +destroy_mstb_topology_history(struct
> > > > > > > > > > > > > > > drm_dp_mst_branch
> > > > > > > > > > > > > > > +*mstb) {
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > +__destroy_topology_ref_history(&mstb-
> > > > > > > > > > > > > > > > topology_ref_history,
> > > > > > > > > > > > > > > +mstb->mgr); }
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > static __always_inline void
> > > > > > > > > > > > > > > dump_mstb_topology_history(struct
> > > > > > > > > > > > > > > drm_dp_mst_branch
> > > > > > > > > > > > > > > *mstb)
> > > > > > > > > > > > > > > {
> > > > > > > > > > > > > > > -
> > > > > > > > > > > > > > > __dump_topology_ref_history(&mstb-
> > > > > > > > > > > > > > > > topology_ref_history,
> > > > > > > > > > > > > > > mstb,
> > > > > > > > > > > > > > > - "MSTB");
> > > > > > > > > > > > > > > + dump_topology_ref_history(&mstb-
> > > > > > > > > > > > > > > > topology_ref_history,
> > > > > > > > > > > > > > > +drm_debug_printer(DBG_PREFIX));
> > > > > > > > > > > > > > > }
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > static __always_inline void
> > > > > > > > > > > > > > > dump_port_topology_history(struct drm_dp_mst_port
> > > > > > > > > > > > > > > *port)
> > > > > > > > > > > > > > > {
> > > > > > > > > > > > > > > -
> > > > > > > > > > > > > > > __dump_topology_ref_history(&port-
> > > > > > > > > > > > > > > > topology_ref_history,
> > > > > > > > > > > > > > > port,
> > > > > > > > > > > > > > > - "Port");
> > > > > > > > > > > > > > > + dump_topology_ref_history(&port-
> > > > > > > > > > > > > > > > topology_ref_history,
> > > > > > > > > > > > > > > +drm_debug_printer(DBG_PREFIX));
> > > > > > > > > > > > > > > }
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > static __always_inline void @@ -1729,6 +1803,14
> > > > > > > > > > > > > > > @@
> > > > > > > > > > > > > > > topology_ref_history_unlock(struct
> > > > > > > > > > > > > > > drm_dp_mst_topology_mgr *mgr) } #else static
> > > > > > > > > > > > > > > inline
> > > > > > > > > > > > > > > void
> > > > > > > > > > > > > > > +init_port_topology_history(struct
> > > > > > > > > > > > > > > drm_dp_mst_topology_mgr
> > > > > > > > > > > > > > > +*mgr, struct drm_dp_mst_port *port); static
> > > > > > > > > > > > > > > inline
> > > > > > > > > > > > > > > void
> > > > > > > > > > > > > > Should also add the bracket, otherwise will get
> > > > > > > > > > > > > > warnings.
> > > > > > > > > > > > > > => static inline void
> > > > > > > > > > > > > > init_port_topology_history(struct
> > > > > > > > > > > > > > drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port
> > > > > > > > > > > > > > *port)
> > > > > > > > > > > > > > {};
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > > +init_mstb_topology_history(struct
> > > > > > > > > > > > > > > drm_dp_mst_topology_mgr
> > > > > > > > > > > > > > > +*mgr, struct drm_dp_mst_branch *mstb); static
> > > > > > > > > > > > > > > inline
> > > > > > > > > > > > > > > void
> > > > > > > > > > > > > > Same as above
> > > > > > > > > > > > > > => static inline void
> > > > > > > > > > > > > > init_mstb_topology_history(struct
> > > > > > > > > > > > > > drm_dp_mst_topology_mgr *mgr, struct
> > > > > > > > > > > > > > drm_dp_mst_branch
> > > > > > > > > > > > > > *mstb)
> > > > > > > > > > > > > > {};
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > > +destroy_port_topology_history(struct
> > > > > > > > > > > > > > > +drm_dp_mst_topology_mgr *mgr, struct
> > > > > > > > > > > > > > > drm_dp_mst_port
> > > > > > > > > > > > > > > +*port); static inline void
> > > > > > > > > > > > > > destroy_port_topology_history() takes one parameter
> > > > > > > > > > > > > > only
> > > > > > > > > > > > > > which
> > > > > > > > > > > > > > is port.
> > > > > > > > > > > > > > => destroy_port_topology_history(struct
> > > > > > > > > > > > > > drm_dp_mst_port
> > > > > > > > > > > > > > *port)
> > > > > > > > > > > > > > {};
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > > +destroy_mstb_topology_history(struct
> > > > > > > > > > > > > > > +drm_dp_mst_topology_mgr *mgr, struct
> > > > > > > > > > > > > > > drm_dp_mst_branch
> > > > > > > > > > > > > > > +*mstb); static inline void
> > > > > > > > > > > > > > destroy_mstb_topology_history() takes one parameter
> > > > > > > > > > > > > > only
> > > > > > > > > > > > > > which
> > > > > > > > > > > > > > is mstb => destroy_mstb_topology_history(struct
> > > > > > > > > > > > > > drm_dp_mst_branch
> > > > > > > > > > > > > > *mstb) {};
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > > topology_ref_history_lock(struct
> > > > > > > > > > > > > > > drm_dp_mst_topology_mgr
> > > > > > > > > > > > > > > *mgr) {} static inline void
> > > > > > > > > > > > > > > topology_ref_history_unlock(struct
> > > > > > > > > > > > > > > drm_dp_mst_topology_mgr *mgr) {} @@ -1740,6
> > > > > > > > > > > > > > > +1822,25
> > > > > > > > > > > > > > > @@
> > > > > > > > > > > > > > > dump_port_topology_history(struct drm_dp_mst_port
> > > > > > > > > > > > > > > *port)
> > > > > > > > > > > > > > > {}
> > > > > > > > > > > > > > > #define save_port_topology_ref(port, type) #endif
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > +static struct drm_dp_mst_branch *
> > > > > > > > > > > > > > > +drm_dp_add_mst_branch_device(struct
> > > > > > > > > > > > > > > drm_dp_mst_topology_mgr
> > > > > > > > > > > > > > > +*mgr,
> > > > > > > > > > > > > > > +u8 lct, u8 *rad) {
> > > > > > > > > > > > > > > + struct drm_dp_mst_branch *mstb;
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > + mstb = kzalloc(sizeof(*mstb), GFP_KERNEL);
> > > > > > > > > > > > > > > + if (!mstb)
> > > > > > > > > > > > > > > + return NULL;
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > + mstb->lct = lct;
> > > > > > > > > > > > > > > + if (lct > 1)
> > > > > > > > > > > > > > > + memcpy(mstb->rad, rad, lct / 2);
> > > > > > > > > > > > > > > + INIT_LIST_HEAD(&mstb->ports);
> > > > > > > > > > > > > > > + kref_init(&mstb->topology_kref);
> > > > > > > > > > > > > > > + kref_init(&mstb->malloc_kref);
> > > > > > > > > > > > > > > + init_mstb_topology_history(mgr, mstb);
> > > > > > > > > > > > > > > + return mstb;
> > > > > > > > > > > > > > > +}
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > static void
> > > > > > > > > > > > > > > drm_dp_destroy_mst_branch_device(struct
> > > > > > > > > > > > > > > kref
> > > > > > > > > > > > > > > *kref) {
> > > > > > > > > > > > > > > struct drm_dp_mst_branch *mstb = @@ -1747,6
> > > > > > > > > > > > > > > +1848,7
> > > > > > > > > > > > > > > @@
> > > > > > > > > > > > > > > static void
> > > > > > > > > > > > > > > drm_dp_destroy_mst_branch_device(struct
> > > > > > > > > > > > > > > kref *kref)
> > > > > > > > > > > > > > > struct drm_dp_mst_topology_mgr *mgr = mstb-
> > > > > > > > > > > > > > > >mgr;
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > dump_mstb_topology_history(mstb);
> > > > > > > > > > > > > > > + destroy_mstb_topology_history(mstb);
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > INIT_LIST_HEAD(&mstb->destroy_next);
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > @@ -1856,6 +1958,7 @@ static void
> > > > > > > > > > > > > > > drm_dp_destroy_port(struct
> > > > > > > > > > > > > > > kref
> > > > > > > > > > > > > > > *kref)
> > > > > > > > > > > > > > > struct drm_dp_mst_topology_mgr *mgr = port-
> > > > > > > > > > > > > > > >mgr;
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > dump_port_topology_history(port);
> > > > > > > > > > > > > > > + destroy_port_topology_history(port);
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > /* There's nothing that needs locking to
> > > > > > > > > > > > > > > destroy
> > > > > > > > > > > > > > > an
> > > > > > > > > > > > > > > input port yet */
> > > > > > > > > > > > > > > if (port->input) {
> > > > > > > > > > > > > > > @@ -2135,7 +2238,7 @@ drm_dp_port_set_pdt(struct
> > > > > > > > > > > > > > > drm_dp_mst_port *port, u8 new_pdt,
> > > > > > > > > > > > > > > ret =
> > > > > > > > > > > > > > > drm_dp_mst_register_i2c_bus(port);
> > > > > > > > > > > > > > > } else {
> > > > > > > > > > > > > > > lct =
> > > > > > > > > > > > > > > drm_dp_calculate_rad(port,
> > > > > > > > > > > > > > > rad);
> > > > > > > > > > > > > > > - mstb =
> > > > > > > > > > > > > > > drm_dp_add_mst_branch_device(lct, rad);
> > > > > > > > > > > > > > > + mstb =
> > > > > > > > > > > > > > > +drm_dp_add_mst_branch_device(mgr, lct, rad);
> > > > > > > > > > > > > > > if (!mstb) {
> > > > > > > > > > > > > > > ret = -ENOMEM;
> > > > > > > > > > > > > > > drm_err(mgr->dev,
> > > > > > > > > > > > > > > "Failed
> > > > > > > > > > > > > > > to
> > > > > > > > > > > > > > > create MSTB for port %p", port); @@ -2366,6
> > > > > > > > > > > > > > > +2469,8 @@
> > > > > > > > > > > > > > > drm_dp_mst_add_port(struct drm_device *dev,
> > > > > > > > > > > > > > > */
> > > > > > > > > > > > > > > drm_dp_mst_get_mstb_malloc(mstb);
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > + init_port_topology_history(mgr, port);
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > return port;
> > > > > > > > > > > > > > > }
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > @@ -3745,7 +3850,7 @@ int
> > > > > > > > > > > > > > > drm_dp_mst_topology_mgr_set_mst(struct
> > > > > > > > > > > > > > > drm_dp_mst_topology_mgr *mgr, bool ms
> > > > > > > > > > > > > > > }
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > /* add initial branch device at LCT
> > > > > > > > > > > > > > > 1 */
> > > > > > > > > > > > > > > - mstb =
> > > > > > > > > > > > > > > drm_dp_add_mst_branch_device(1,
> > > > > > > > > > > > > > > NULL);
> > > > > > > > > > > > > > > + mstb =
> > > > > > > > > > > > > > > drm_dp_add_mst_branch_device(mgr,
> > > > > > > > > > > > > > > 1,
> > > > > > > > > > > > > > > +NULL);
> > > > > > > > > > > > > > > if (mstb == NULL) {
> > > > > > > > > > > > > > > ret = -ENOMEM;
> > > > > > > > > > > > > > > goto out_unlock; @@ -5512,14
> > > > > > > > > > > > > > > +5617,16
> > > > > > > > > > > > > > > @@ int drm_dp_mst_topology_mgr_init(struct
> > > > > > > > > > > > > > > drm_dp_mst_topology_mgr *mgr,
> > > > > > > > > > > > > > > mutex_init(&mgr->delayed_destroy_lock);
> > > > > > > > > > > > > > > mutex_init(&mgr->up_req_lock);
> > > > > > > > > > > > > > > mutex_init(&mgr->probe_lock); -#if
> > > > > > > > > > > > > > > IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS)
> > > > > > > > > > > > > > > - mutex_init(&mgr->topology_ref_history_lock);
> > > > > > > > > > > > > > > -#endif
> > > > > > > > > > > > > > > INIT_LIST_HEAD(&mgr->tx_msg_downq);
> > > > > > > > > > > > > > > INIT_LIST_HEAD(&mgr->destroy_port_list);
> > > > > > > > > > > > > > > INIT_LIST_HEAD(&mgr-
> > > > > > > > > > > > > > > > destroy_branch_device_list);
> > > > > > > > > > > > > > > INIT_LIST_HEAD(&mgr->up_req_list);
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > +#if
> > > > > > > > > > > > > > > IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS)
> > > > > > > > > > > > > > > + mutex_init(&mgr->topology_ref_history_lock);
> > > > > > > > > > > > > > > + INIT_LIST_HEAD(&mgr-
> > > > > > > > > > > > > > > >topology_ref_history_list);
> > > > > > > > > > > > > > > +#endif
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > /*
> > > > > > > > > > > > > > > * delayed_destroy_work will be queued on a
> > > > > > > > > > > > > > > dedicated
> > > > > > > > > > > > > > > WQ, so that any
> > > > > > > > > > > > > > > * requeuing will be also flushed when
> > > > > > > > > > > > > > > deiniting
> > > > > > > > > > > > > > > the
> > > > > > > > > > > > > > > topology manager.
> > > > > > > > > > > > > > > diff --git
> > > > > > > > > > > > > > > a/drivers/gpu/drm/nouveau/nouveau_debugfs.c
> > > > > > > > > > > > > > > b/drivers/gpu/drm/nouveau/nouveau_debugfs.c
> > > > > > > > > > > > > > > index 1cbe01048b93..53ec7c1daada 100644
> > > > > > > > > > > > > > > --- a/drivers/gpu/drm/nouveau/nouveau_debugfs.c
> > > > > > > > > > > > > > > +++ b/drivers/gpu/drm/nouveau/nouveau_debugfs.c
> > > > > > > > > > > > > > > @@ -29,9 +29,13 @@
> > > > > > > > > > > > > > > */
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > #include <linux/debugfs.h>
> > > > > > > > > > > > > > > +#include <drm/drm_dp_mst_helper.h> #include
> > > > > > > > > > > > > > > +<drm/drm_encoder.h>
> > > > > > > > > > > > > > > #include <nvif/class.h>
> > > > > > > > > > > > > > > #include <nvif/if0001.h>
> > > > > > > > > > > > > > > +#include <nouveau_encoder.h>
> > > > > > > > > > > > > > > #include "nouveau_debugfs.h"
> > > > > > > > > > > > > > > +#include "nouveau_display.h"
> > > > > > > > > > > > > > > #include "nouveau_drv.h"
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > static int
> > > > > > > > > > > > > > > @@ -68,6 +72,34 @@
> > > > > > > > > > > > > > > nouveau_debugfs_strap_peek(struct
> > > > > > > > > > > > > > > seq_file *m, void
> > > > > > > > > > > > > > > *data)
> > > > > > > > > > > > > > > return 0;
> > > > > > > > > > > > > > > }
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > +#ifdef CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS
> > > > > > > > > > > > > > > +static int
> > > > > > > > > > > > > > > nouveau_debugfs_mst_topology_history(struct
> > > > > > > > > > > > > > > +seq_file *m, void *data) {
> > > > > > > > > > > > > > > + struct drm_info_node *node = m->private;
> > > > > > > > > > > > > > > + struct drm_device *dev = node->minor->dev;
> > > > > > > > > > > > > > > + struct drm_encoder *encoder;
> > > > > > > > > > > > > > > + struct nouveau_display *disp =
> > > > > > > > > > > > > > > nouveau_display(dev);
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > + if (disp->disp.object.oclass < GF110_DISP)
> > > > > > > > > > > > > > > + return -EINVAL;
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > + drm_for_each_encoder(encoder, dev) {
> > > > > > > > > > > > > > > + struct nv50_mstm *mstm;
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > + /* We need the real encoder for each
> > > > > > > > > > > > > > > MST
> > > > > > > > > > > > > > > mgr
> > > > > > > > > > > > > > > +*/
> > > > > > > > > > > > > > > + if (encoder->encoder_type !=
> > > > > > > > > > > > > > > +DRM_MODE_ENCODER_TMDS)
> > > > > > > > > > > > > > > + continue;
> > > > > > > > > > > > > > > + mstm = nouveau_encoder(encoder)-
> > > > > > > > > > > > > > > > dp.mstm;
> > > > > > > > > > > > > > > + if (!mstm)
> > > > > > > > > > > > > > > + continue;
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > + seq_printf(m, "MSTM on %s:\n",
> > > > > > > > > > > > > > > encoder-
> > > > > > > > > > > > > > > > name);
> > > > > > > > > > > > > > > + drm_dp_mst_dump_topology_refs(m,
> > > > > > > > > > > > > > > &mstm-
> > > > > > > > > > > > > > > > mgr);
> > > > > > > > > > > > > > > + }
> > > > > > > > > > > > > > > + return 0;
> > > > > > > > > > > > > > > +}
> > > > > > > > > > > > > > > +#endif
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > static int
> > > > > > > > > > > > > > > nouveau_debugfs_pstate_get(struct seq_file *m,
> > > > > > > > > > > > > > > void
> > > > > > > > > > > > > > > *data)
> > > > > > > > > > > > > > > { @@
> > > > > > > > > > > > > > > -213,6
> > > > > > > > > > > > > > > +245,9 @@ static const struct file_operations
> > > > > > > > > > > > > > > nouveau_pstate_fops = { static struct
> > > > > > > > > > > > > > > drm_info_list
> > > > > > > > > > > > > > > nouveau_debugfs_list[] = {
> > > > > > > > > > > > > > > { "vbios.rom", nouveau_debugfs_vbios_image,
> > > > > > > > > > > > > > > 0,
> > > > > > > > > > > > > > > NULL
> > > > > > > > > > > > > > > },
> > > > > > > > > > > > > > > { "strap_peek", nouveau_debugfs_strap_peek,
> > > > > > > > > > > > > > > 0,
> > > > > > > > > > > > > > > NULL
> > > > > > > > > > > > > > > },
> > > > > > > > > > > > > > > +#ifdef CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS
> > > > > > > > > > > > > > > + { "dp_mst_topology_refs",
> > > > > > > > > > > > > > > +nouveau_debugfs_mst_topology_history, 0, NULL },
> > > > > > > > > > > > > > > #endif
> > > > > > > > > > > > > > > };
> > > > > > > > > > > > > > > #define NOUVEAU_DEBUGFS_ENTRIES
> > > > > > > > > > > > > > > ARRAY_SIZE(nouveau_debugfs_list)
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > diff --git a/include/drm/drm_dp_mst_helper.h
> > > > > > > > > > > > > > > b/include/drm/drm_dp_mst_helper.h index
> > > > > > > > > > > > > > > 78044ac5b59b..e3a73d8d97c0
> > > > > > > > > > > > > > > 100644
> > > > > > > > > > > > > > > --- a/include/drm/drm_dp_mst_helper.h
> > > > > > > > > > > > > > > +++ b/include/drm/drm_dp_mst_helper.h
> > > > > > > > > > > > > > > @@ -35,6 +35,11 @@ enum
> > > > > > > > > > > > > > > drm_dp_mst_topology_ref_type {
> > > > > > > > > > > > > > > DRM_DP_MST_TOPOLOGY_REF_PUT,
> > > > > > > > > > > > > > > };
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > +enum drm_dp_mst_topology_history_type {
> > > > > > > > > > > > > > > + DRM_DP_MST_TOPOLOGY_HISTORY_PORT,
> > > > > > > > > > > > > > > + DRM_DP_MST_TOPOLOGY_HISTORY_MSTB, };
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > struct drm_dp_mst_topology_ref_history {
> > > > > > > > > > > > > > > struct drm_dp_mst_topology_ref_entry {
> > > > > > > > > > > > > > > enum drm_dp_mst_topology_ref_type
> > > > > > > > > > > > > > > type;
> > > > > > > > > > > > > > > @@
> > > > > > > > > > > > > > > -43,6
> > > > > > > > > > > > > > > +48,9 @@ struct drm_dp_mst_topology_ref_history {
> > > > > > > > > > > > > > > depot_stack_handle_t backtrace;
> > > > > > > > > > > > > > > } *entries;
> > > > > > > > > > > > > > > int len;
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > + enum drm_dp_mst_topology_history_type type;
> > > > > > > > > > > > > > > + struct list_head node;
> > > > > > > > > > > > > > > };
> > > > > > > > > > > > > > > #endif /*
> > > > > > > > > > > > > > > IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS)
> > > > > > > > > > > > > > > */
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > @@ -769,6 +777,12 @@ struct
> > > > > > > > > > > > > > > drm_dp_mst_topology_mgr {
> > > > > > > > > > > > > > > * &drm_dp_mst_branch.topology_ref_history.
> > > > > > > > > > > > > > > */
> > > > > > > > > > > > > > > struct mutex topology_ref_history_lock;
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > + /**
> > > > > > > > > > > > > > > + * @topology_ref_history_list: contains a
> > > > > > > > > > > > > > > list
> > > > > > > > > > > > > > > of
> > > > > > > > > > > > > > > +topology ref
> > > > > > > > > > > > > > > histories for any MSTBs or
> > > > > > > > > > > > > > > + * ports that are still in memory
> > > > > > > > > > > > > > > + */
> > > > > > > > > > > > > > > + struct list_head topology_ref_history_list;
> > > > > > > > > > > > > > > #endif
> > > > > > > > > > > > > > > };
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > @@ -873,6 +887,10 @@ void
> > > > > > > > > > > > > > > drm_dp_mst_put_port_malloc(struct
> > > > > > > > > > > > > > > drm_dp_mst_port *port);
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > struct drm_dp_aux
> > > > > > > > > > > > > > > *drm_dp_mst_dsc_aux_for_port(struct
> > > > > > > > > > > > > > > drm_dp_mst_port *port);
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > +#ifdef CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS
> > > > > > > > > > > > > > > +void drm_dp_mst_dump_topology_refs(struct
> > > > > > > > > > > > > > > seq_file
> > > > > > > > > > > > > > > *m,
> > > > > > > > > > > > > > > +struct drm_dp_mst_topology_mgr *mgr); #endif
> > > > > > > > > > > > > > > +
> > > > > > > > > > > > > > > extern const struct drm_private_state_funcs
> > > > > > > > > > > > > > > drm_dp_mst_topology_state_funcs;
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > /**
> > > > > > > > > > > > > > > --
> > > > > > > > > > > > > > > 2.31.1
> > > > > > > > > > > > > >
> > > > > > > > > > > > >
> > > > > > > > > > > > > --
> > > > > > > > > > > > > Cheers,
> > > > > > > > > > > > > Lyude Paul (she/her)
> > > > > > > > > > > > > Software Engineer at Red Hat
> > > > > > > > > > >
> > > > > > > > > >
> > > > > > > > >
> > > > > > > > > --
> > > > > > > > > Cheers, Lyude Paul (she/her) Software Engineer at Red Hat
> > > > > > > > --
> > > > > > > > Regards,
> > > > > > > > Wayne Lin
> > > > > > > >
> > > > > > >
> > > > > > > --
> > > > > > > Cheers,
> > > > > > > Lyude Paul (she/her)
> > > > > > > Software Engineer at Red Hat
> > > > > >
> > > > >
> > > >
> > >
> > > --
> > > Cheers,
> > > Lyude Paul (she/her)
> > > Software Engineer at Red Hat
> >
>
> --
> Cheers,
> Lyude Paul (she/her)
> Software Engineer at Red Hat
--
Regards,
Wayne Lin
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