[PATCH 0/2] Fix observed mst problems with StarTech hub

[Lin, Wayne]

[Public]

Thanks Lyude for the review!

For the 1st patch, it's trying to fix the patch
7617e9621bf2 ("drm/dp_mst: clear time slots for ports invalid").

As for the 2nd one, it's my first time to test on this hub and I not
yet know the exact regression point. I'm also not quite sure if this
regression is caused by driver or just behavior changes from upper layer.
I was thinking that this patch is just an enhancement for our mst
helper functions and should be applicable for older kernel versions.

Thanks for your time!

Regards,
Wayne
________________________________________
> From: Lyude Paul <lyude at redhat.com>
> Sent: Saturday, June 12, 2021 06:43
> To: Lin, Wayne; dri-devel at lists.freedesktop.org
> Cc: Kazlauskas, Nicholas; Wentland, Harry; Zuo, Jerry; Pillai, Aurabindo
> Subject: Re: [PATCH 0/2] Fix observed mst problems with StarTech hub
>
> haha. turns out it actually was a good thing I was busy with work today,
> because I ended up testing some backports and running into the exact same MST
> bug these patches appear to fix. How convienent :)
>
> anyway-I looked over this and this looks good to me (and IMO, I like these
> fixes more then the workarounds they replace!). The one thing we do need to
> fix here though is this appears to definitely fix a regression, so we need to
> make sure we actually bisect the issue that this patch is fixing so we can add
> the appropriate Fixes: and Cc: tags so that these fixes get backported to
> earlier stable kernel versions.
>
> I definitely need this fix in asap though for my own work, so I am going to
> see if I can start bisecting this. If I manage to figure out what's breaking
> it before my workday ends today I'll just add my R-b and push this upstream,
> otherwise I'll probably just push this first thing on monday. If you see this
> message beforethen and know what kernel version introduced this issue, feel
> free to respond ;)
>
> On Fri, 2021-05-28 at 21:55 +0800, Wayne Lin wrote:
> > Use Startech 1to3 DP hub to do some mst hotplug tests and find some
> > light up issues.
> >
> > 1. ACT polling timeout:
> >    Which is due to we didn't update DPCD payload table but still try
> >    to send ACT and polling for "ACT Handled" bit
> > 2. Not all monitors light up:
> >    Due to we wrongly set unavailable VCP ID for new streams
> >
> > Wayne Lin (2):
> >   drm/dp_mst: Do not set proposed vcpi directly
> >   drm/dp_mst: Avoid to mess up payload table by ports in stale topology
> >
> >  drivers/gpu/drm/drm_dp_mst_topology.c | 65 ++++++++++++++++-----------
> >  1 file changed, 39 insertions(+), 26 deletions(-)
> >
>
> --
> Cheers,
>  Lyude Paul (she/her)
>  Software Engineer at Red Hat