[Intel-gfx] [PATCH] drm/i915: flush delayed_resume_work when suspending

[Paulo Zanoni]

2014-06-27 19:30 GMT-03:00 Rodrigo Vivi <rodrigo.vivi at gmail.com>:
> I have the feeling the safest side would be disable rc6 on resume instead of
> force its enabling... or am I missing something?

It will be enabled, then disabled.

> why don't you just cancel the work? and put another after resume?
>
> but if the patch really solves the problem and this is what you meant feel
> free to use:

What you're suggesting is the "We could also" case mentioned in the
second paragraph of the commit message. I even wrote and tested that
patch, but Jesse seemed to prefer the "flush" version instead of the
"cancel" one. I'll send the other version to the list, then reviewers
and maintainers can decide which one they prefer :)

> Reviewed-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
>
>
>
> On Fri, Jun 27, 2014 at 2:51 PM, Paulo Zanoni <przanoni at gmail.com> wrote:
>>
>> From: Paulo Zanoni <paulo.r.zanoni at intel.com>
>>
>> It is possible that, by the time we run i915_drm_freeze(),
>> delayed_resume_work was already queued but did not run yet. If it
>> still didn't run after intel_runtime_pm_disable_interrupts(), by the
>> time it runs it will try to change the interrupt registers with the
>> interrupts already disabled, which will trigger a WARN. We can
>> reliably reproduce this with the pm_rpm system-suspend test case.
>>
>> In order to avoid the problem, we have to flush the work before
>> disabling the interrupts. We could also cancel the work instead of
>> flushing it, but that would require us to put a runtime PM reference -
>> and any other resource we may need in the future - in case the work
>> was already queued, so I believe flushing the work is more
>> future-proof, although less efficient. But I can also change this part
>> if someone requests.
>>
>> Another thing I tried was to move the intel_suspend_gt_powersave()
>> call to before intel_runtime_pm_disable_interrupts(), but since that
>> function needs to be called after the interrupts are already disabled,
>> due to dev_priv->rps.work, this strategy didn't work.
>>
>> Testcase: igt/pm_rpm/system-suspend
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=80517
>> Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>
>> ---
>>  drivers/gpu/drm/i915/i915_drv.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/i915/i915_drv.c
>> b/drivers/gpu/drm/i915/i915_drv.c
>> index e64547e..672694b 100644
>> --- a/drivers/gpu/drm/i915/i915_drv.c
>> +++ b/drivers/gpu/drm/i915/i915_drv.c
>> @@ -524,6 +524,8 @@ static int i915_drm_freeze(struct drm_device *dev)
>>                         return error;
>>                 }
>>
>> +               flush_delayed_work(&dev_priv->rps.delayed_resume_work);
>> +
>>                 intel_runtime_pm_disable_interrupts(dev);
>>                 dev_priv->enable_hotplug_processing = false;
>>
>> --
>> 2.0.0
>>
>> _______________________________________________
>> Intel-gfx mailing list
>> Intel-gfx at lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
>
>
>
> --
> Rodrigo Vivi
> Blog: http://blog.vivi.eng.br
>



-- 
Paulo Zanoni