[Intel-gfx] [DMC_BUGFIX_SKL_V2 1/5] drm/i915/skl: Added a check for the hardware status of csr fw before loading.
Rafael J. Wysocki
rafael.j.wysocki at intel.com
Tue Sep 29 17:50:40 PDT 2015
On 9/29/2015 10:51 AM, Daniel Vetter wrote:
> On Tue, Sep 29, 2015 at 01:54:53AM +0200, Rafael J. Wysocki wrote:
>> On 9/28/2015 8:52 AM, Daniel Vetter wrote:
>>> On Wed, Sep 23, 2015 at 10:49:36PM +0200, Rafael J. Wysocki wrote:
>>>> On 9/23/2015 7:17 PM, Daniel Vetter wrote:
>>>>> acpi_target_system_state() seems to be almost the thing we're looking
>>>>> for, except that it's only valid in the suspend callbacks since it
>>>>> gets reset to ACPI_STATE_S0 when resuming. So probably we want
>>>>> something else ...
>>>> Right.
>>>>
>>>> The idea is to add a way for drivers to check if
>>>> (a) suspend is going to enter the BIOS
>>>> (b) resume has been triggered by the BIOS
>>>> and that's really what drivers need to know.
>>>>
>>>> For suspend-to-idle those two will return false and for S3 they'll return
>>>> true.
>>>>
>>>> Would that help?
>>> Not sure that matches exaxtly what we'd need here ... Essentially we need
>>> to know whether we've been in S3/S4 (firmware has been eaten) or in one of
>>> the higher suspend-to-idle/standby states (firmware still alive, don't
>>> disturb it). Additional fun that just crossed my mind is that if the
>>> suspend-to-mem is aborted (some other driver failed) then that function
>>> should _not_ indicate that we've been in S3. So maybe something like
>> So it really looks like the interface I was talking about would be suitable:
>>
>> pm_suspend_via_firmware() == true -> firmware is going to be eaten (use that
>> during suspend if needed)
>> pm_resume_via_firmware() == true -> firmware was eaten
>>
>> The latter will only return 'true' if we really have entered the BIOS
>> (platform firmware).
> Yeah that seems to fit the bill. We already have a check in our suspend
> paths to figure out whether we'll suspend to idle or go into full S3, so
> i915 could use them both. And making them generic would make sense I
> guess.
OK, sent patches (CCed you), please have a look.
Thanks,
Rafael
>>> acpi_source_system_state() which usually is S0 and only when acpi
>>> successfully went into the suspend state in platform_suspend_ops->enter it
>>> gets set to the value of acpi_target_system_state. And then reset once the
>>> resume has completed. I think that would be what we'd want here.
>> We need to new functions like the above, because some things already depend
>> on acpi_target_system_state working the way it does currently.
>>
>> I see no reason to make that ACPI-specific, though, in principle.
>>
>>> Anyway I'll pull in Animesh series meanwhile, amended with a FIXME comment.
>> Fine by me.
>>
>> Thanks,
>> Rafael
>>
>>
>>>>> On Wed, Sep 23, 2015 at 6:28 PM, Daniel Vetter <daniel at ffwll.ch> wrote:
>>>>>> Actually add Rafael this time around ...
>>>>>> -Daniel
>>>>>>
>>>>>> On Wed, Sep 23, 2015 at 6:27 PM, Daniel Vetter <daniel at ffwll.ch> wrote:
>>>>>>> On Wed, Sep 23, 2015 at 9:57 AM, Daniel Vetter <daniel at ffwll.ch> wrote:
>>>>>>>> On Thu, Sep 17, 2015 at 12:53:21AM +0530, Animesh Manna wrote:
>>>>>>>>> On 9/14/2015 1:16 PM, Daniel Vetter wrote:
>>>>>>>>>> On Fri, Sep 11, 2015 at 12:36:24AM +0530, Animesh Manna wrote:
>>>>>>>>>>> On 9/10/2015 8:15 PM, Daniel Vetter wrote:
>>>>>>>>>>>> On Thu, Sep 10, 2015 at 01:58:54AM +0530, Animesh Manna wrote:
>>>>>>>>>>>>> On 9/2/2015 2:24 PM, Daniel Vetter wrote:
>>>>>>>>>>>>>> On Wed, Aug 26, 2015 at 07:40:54PM +0530, Animesh Manna wrote:
>>>>>>>>>>>>>>> On 8/26/2015 6:40 PM, Daniel Vetter wrote:
>>>>>>>>>>>>>>>> On Wed, Aug 26, 2015 at 01:36:05AM +0530, Animesh Manna wrote:
>>>>>>>>>>>>>>>>> Dmc will restore the csr program except DC9, cold boot,
>>>>>>>>>>>>>>>>> warm reset, PCI function level reset, and hibernate/suspend.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> intel_csr_load_program() function is used to load the firmware
>>>>>>>>>>>>>>>>> data from kernel memory to csr address space.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> All values of csr address space will be zero if it got reset and
>>>>>>>>>>>>>>>>> the first byte of csr program is always a non-zero if firmware
>>>>>>>>>>>>>>>>> is loaded successfuly. Based on hardware status will load the
>>>>>>>>>>>>>>>>> firmware.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Without this condition check if we overwrite the firmware data the
>>>>>>>>>>>>>>>>> counters exposed for dc5/dc6 (help for debugging) will be nullified.
>>>>>>>>>>>>>>> Bacause of the above reason mentioned just above we need to block firmware loading again.
>>>>>>>>>>>>>>> So only WARN_ON will not help.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> v1: Initial version.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> v2: Based on review comments from Daniel,
>>>>>>>>>>>>>>>>> - Added a check to know hardware status and load the firmware if not loaded.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Cc: Daniel Vetter <daniel.vetter at intel.com>
>>>>>>>>>>>>>>>>> Cc: Damien Lespiau <damien.lespiau at intel.com>
>>>>>>>>>>>>>>>>> Cc: Imre Deak <imre.deak at intel.com>
>>>>>>>>>>>>>>>>> Cc: Sunil Kamath <sunil.kamath at intel.com>
>>>>>>>>>>>>>>>>> Signed-off-by: Animesh Manna <animesh.manna at intel.com>
>>>>>>>>>>>>>>>>> Signed-off-by: Vathsala Nagaraju <vathsala.nagaraju at intel.com>
>>>>>>>>>>>>>>>>> ---
>>>>>>>>>>>>>>>>> drivers/gpu/drm/i915/intel_csr.c | 9 +++++++++
>>>>>>>>>>>>>>>>> 1 file changed, 9 insertions(+)
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> diff --git a/drivers/gpu/drm/i915/intel_csr.c b/drivers/gpu/drm/i915/intel_csr.c
>>>>>>>>>>>>>>>>> index ba1ae03..682cc26 100644
>>>>>>>>>>>>>>>>> --- a/drivers/gpu/drm/i915/intel_csr.c
>>>>>>>>>>>>>>>>> +++ b/drivers/gpu/drm/i915/intel_csr.c
>>>>>>>>>>>>>>>>> @@ -252,6 +252,15 @@ void intel_csr_load_program(struct drm_device *dev)
>>>>>>>>>>>>>>>>> return;
>>>>>>>>>>>>>>>>> }
>>>>>>>>>>>>>>>>> + /*
>>>>>>>>>>>>>>>>> + * Dmc will restore the csr the program except DC9, cold boot,
>>>>>>>>>>>>>>>>> + * warm reset, PCI function level reset, and hibernate/suspend.
>>>>>>>>>>>>>>>>> + * This condition will help to check if csr address space is reset/
>>>>>>>>>>>>>>>>> + * not loaded.
>>>>>>>>>>>>>>>>> + */
>>>>>>>>>>>>>>>> Atm we call this from driver load and resume, which doesn seem to cover
>>>>>>>>>>>>>>>> all the cases you mention in the comment. Should this be a WARN_ON
>>>>>>>>>>>>>>>> instead? Or do we have troubles in our init sequence where we load too
>>>>>>>>>>>>>>>> many times?
>>>>>>>>>>>>>>> Yes, the above statement taken from bspec to describe about the special cases dmc will not restore the firmware.
>>>>>>>>>>>>>>> Agree, In our cases cold boot and hibernate/suspend mainly we need to load the firmware again, so in my
>>>>>>>>>>>>>>> second sentence I wanted to comment mainly regarding this condition check added for suspend-hibernate(reset)
>>>>>>>>>>>>>>> and cold boot(not loaded).
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Anyways the same api later can be used to load the firmware from anywhere, so my intention to check firmware loaded or not.
>>>>>>>>>>>>>>> If already loaded then not to overwrite the csr address space to maintain the dc5/dc6 counter value.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Can the below comment more clear to you.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> /*
>>>>>>>>>>>>>>> * Dmc will restore the csr the program except DC9, cold boot,
>>>>>>>>>>>>>>> * warm reset, PCI function level reset, and hibernate/suspend.
>>>>>>>>>>>>>>> * If firmware is restored by dmc then no need to load again which
>>>>>>>>>>>>>>> * will keep the dc5/dc6 counter exposed by firmware.
>>>>>>>>>>>>>>> */
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> No issue in init sequence.
>>>>>>>>>>>>>> That seems to still cover all the callers of the function afaics - we do
>>>>>>>>>>>>>> pci resets over suspend resume unconditionally. So I still don't
>>>>>>>>>>>>>> understand where exactly we try to load the dmc firmware in i915.ko when
>>>>>>>>>>>>>> it's already loaded.
>>>>>>>>>>>>> During resume intel_csr_load_program() will be called from
>>>>>>>>>>>>> intel_runtime_resume().
>>>>>>>>>>>>>
>>>>>>>>>>>>> intel_runtime_resume()-> skl_resume_prepare()-> intel_csr_load_program()
>>>>>>>>>>>>>
>>>>>>>>>>>>> During Pc10 entry testing I can see dmc is restoring back the firmware always,
>>>>>>>>>>>>> but as you mentioned pci-reset can happen unconditionally, but still then
>>>>>>>>>>>>> also during resume intel_runtime_resume() will be called and based on
>>>>>>>>>>>>> register read of csr-base-address firmware loading will happen.
>>>>>>>>>>>> But in your comment you're saying it won't get restored in case of dc9 and
>>>>>>>>>>>> suspend. So that seems to mismatch what you're saying here (and what the
>>>>>>>>>>>> commit message says) and what the code does. And this function here is
>>>>>>>>>>>> called for resume after suspend/hibernate only.
>>>>>>>>>>> pc10 entry explanation I told is for skylake. dc9 in skylake is not possible.
>>>>>>>>>>> I think you are confusing between dc6 and dc9. Pc10 can be achieved by
>>>>>>>>>>> entering into dc6 (not dc9) for skylake. dc9 is the lowest possible state
>>>>>>>>>>> for broxton which is not present for skylake.
>>>>>>>>>> I have no idea at all about different pc levels on skl. What I'm talking
>>>>>>>>>> about is system suspend/resume and driver load, which are the places this
>>>>>>>>>> function gets called. At least afaics.
>>>>>>>>>>
>>>>>>>>>>> Here intel_csr_load_program() will be used for both skylake and broxton, and instruction
>>>>>>>>>>> execution flow will be different in case of suspend/resume which I think is confusing
>>>>>>>>>>> you.
>>>>>>>>>> That seems like really important information. What's different on bxt?
>>>>>>>>>> These are the kind of details you should explain in the commit message ...
>>>>>>>>>>
>>>>>>>>>>> I am ready explain you in detail. It will be good if we discuss specific use-case scenario
>>>>>>>>>>> and itz software design for specific platform. Another point - as dmc related code for
>>>>>>>>>>> broxton is not merged better first we close design for skylake. Now, I have added dc9
>>>>>>>>>>> description in comment thinking of future. If you want I can remove for now and later
>>>>>>>>>>> can add in bxt patch series for enabling dmc. Will wait for your reply.
>>>>>>>>>> This question here isn't about the overall design and how to handle power
>>>>>>>>>> wells in skl/bxt. That's a separate discussion and tracked somewhere else.
>>>>>>>>>> I'm really just confused about when exactly we need to reload to firmware,
>>>>>>>>>> and why we need a runtime check for that. Normally we should know when to
>>>>>>>>>> reload the firmware and just either reload or not, without checking hw
>>>>>>>>>> state. And I don't like checking for hw state since at least in the past
>>>>>>>>>> that kind of code ended up being fragile - it's an illusion that it does
>>>>>>>>>> the right thing no matter what, since often there's other tricky ordering
>>>>>>>>>> constraints. And if you have automatic duct-tape like then no one will
>>>>>>>>>> ever spot those other, harder to spot issues, until an expensive customer
>>>>>>>>>> escalation happens.
>>>>>>>>>>
>>>>>>>>>> So what I want to know here is:
>>>>>>>>>> - When exactly do we need to reload dmc firmware.
>>>>>>>>> In skl, during driver load first time we load the firmware, during normal
>>>>>>>>> suspend-resume (dc6 entry/exit)
>>>>>>>>> no need to reload the firmware again as dmc will take care of it. But during
>>>>>>>>> suspend/hibernation
>>>>>>>>> dmc will not restore the firmware. In that case driver need to reload it
>>>>>>>>> again. I do not know
>>>>>>>>> how to differentiate pm-suspend and suspend-hibernation and thought both the
>>>>>>>>> cases
>>>>>>>>> intel_runtime_resume() will be called where we can check the h/w state and
>>>>>>>>> reload the
>>>>>>>>> firmware if dmc is not restored.
>>>>>>>>>
>>>>>>>>> In bxt, during driver load first time we load the firmware, during normal
>>>>>>>>> suspend-resume
>>>>>>>>> display engine will enter into dc9 and dmc will not restore the firmware. So
>>>>>>>>> every
>>>>>>>>> suspend-resume we need to reload the firmware.
>>>>>>>>>> - What exactly is the reason why we can't make that decision statically in
>>>>>>>>>> the code (by calling csr_load at the right spots).
>>>>>>>>> As I mentioned before in case of skylake can we differentiate between
>>>>>>>>> "resume from pm-suspend" with "resume from suspend-hibernation" inside
>>>>>>>>> driver?
>>>>>>>>>
>>>>>>>>> In case of broxton, every time we need to reload, so we can decide
>>>>>>>>> statically.
>>>>>>>> Of course we can differentiate between all the different resume paths, and
>>>>>>>> we also have a per-platform split to take care of bxt vs. skl. And there
>>>>>>>> are actually 3 different resume paths:
>>>>>>>>
>>>>>>>> - runtime PM resume. This calls the runtime_resume hook. It sounds like on
>>>>>>>> skl we should _not_ load the csr firmware, but on bxt we should load it.
>>>>>>>> This can be fixed by removing the intel_csr_load_program call from
>>>>>>>> skl_resume_prepare.
>>>>>>>> - resume from hibernate-to-disk (i.e. system completely off, state stored
>>>>>>>> on the swap partition) is done by calling the thaw callbacks.
>>>>>>>> - resume from suspend-to-mem (i.e. system in low-power with only memory
>>>>>>>> in self-refresh, all state stored in memory) is done by calling the
>>>>>>>> resume callbacks.
>>>>>>>>
>>>>>>>> For i915 we use unified handlers in our dev_pm_ops for both thaw and
>>>>>>>> resume, but it sounds like that won't be a problem for skl/bxt since we
>>>>>>>> need to reload the csr firmware in all cases. Although I'm not perfectly
>>>>>>>> sure since you don't explain what kind of resume you mean exactly (since
>>>>>>>> you don't use the linux names for them).
>>>>>>>>
>>>>>>>> Anyway it sounds like we can replace this patch by one where we remove
>>>>>>>> that errornous csr load call from skl runtime pm resume and that's all.
>>>>>>>> But I suggest to make sure we get this right we keep the check you're
>>>>>>>> adding here, but wrap it in a WARN_ON. Then we'll get a backtrace when
>>>>>>>> this is going wrong again. Like this:
>>>>>>>>
>>>>>>>> if (WARN_ON(csr_loaded_already()))
>>>>>>>> return;
>>>>>>>>
>>>>>>>> Also when redoing the commits please explain in detail what exactly are
>>>>>>>> the requirements like you've done above, but please use the standard linux
>>>>>>>> names, i.e. "runtime PM" and "hibernate-to-disk" and "suspend-to-mem".
>>>>>>> Ok hooray there's more suspend-to-something things I've totally missed:
>>>>>>> - suspend-to-idle (done by cat freeze > /sys/power/state) and
>>>>>>> - suspend (done by cat suspend > /sys/power/state)
>>>>>>>
>>>>>>> And apparently there's really no way to drivers to tell them apart.
>>>>>>> Rafael, is there really no way for drivers to take different paths for
>>>>>>> these 3 suspend cases? I tried grepping for PM_SUSPEND_ON/STANDY/MEM
>>>>>>> and didn't spot anything.
>>>>>>>
>>>>>>> Also we're completely missing test coverage for that in igt. That is
>>>>>>> something that needs to be fixed asap (yet another case of
>>>>>>> combinatorial explosion in igt tests, yay). And at least one of those
>>>>>>> suspend-to-idle testcase better be in the BAT.
>>>>>>> -Daniel
>>>>>>> --
>>>>>>> Daniel Vetter
>>>>>>> Software Engineer, Intel Corporation
>>>>>>> +41 (0) 79 365 57 48 - http://blog.ffwll.ch
>>>>>> --
>>>>>> Daniel Vetter
>>>>>> Software Engineer, Intel Corporation
>>>>>> +41 (0) 79 365 57 48 - http://blog.ffwll.ch
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