[Intel-gfx] [PATCH] drm/i915/gt: Clear wedged status upon suspend

[Rodrigo Vivi]

On Tue, Jan 24, 2023 at 12:07:19PM +0100, Das, Nirmoy wrote:
> Forgot to add the drm issue a reference.
> 
> On 1/24/2023 12:05 PM, Nirmoy Das wrote:
> > From: Chris Wilson <chris.p.wilson at linux.intel.com>
> > 
> > Currently we use set-wedged on suspend if the workload is not responding
> > in order to allow a fast suspend (albeit at the cost of discarding the
> > current userspace). This may leave the device wedged during suspend,
> > where we may require the device available in order to swapout CPU
> > inaccessible device memory. Clear any temporary wedged-status after
> > flushing userspace off the device so we can use the blitter ourselves
> > inside suspend.

This seems a very good move. But this explain they unset_wedged part,
not the removal of the retire_requests. Why don't we need to retire them
anymore?

Also, what are the chances of races here? I mean, we are marking
the gpu as not wedged anymore. Do we have any warranty at this point
that no further request will arrive?

Shouldn't we have a way to differentiate between the totally wedged
and blocked for user submission?

> > 
> > Testcase: igt/gem_eio/in-flight-suspend
> References: https://gitlab.freedesktop.org/drm/intel/-/issues/7896
> > Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> > Signed-off-by: Chris Wilson <chris.p.wilson at linux.intel.com>
> > Signed-off-by: Nirmoy Das <nirmoy.das at intel.com>
> > ---
> >   drivers/gpu/drm/i915/gt/intel_gt_pm.c | 10 ++++------
> >   1 file changed, 4 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/gt/intel_gt_pm.c b/drivers/gpu/drm/i915/gt/intel_gt_pm.c
> > index cef3d6f5c34e..74d1dd3793f9 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_gt_pm.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_gt_pm.c
> > @@ -317,19 +317,17 @@ int intel_gt_resume(struct intel_gt *gt)
> >   static void wait_for_suspend(struct intel_gt *gt)
> >   {
> > -	if (!intel_gt_pm_is_awake(gt))
> > -		return;
> > -
> > -	if (intel_gt_wait_for_idle(gt, I915_GT_SUSPEND_IDLE_TIMEOUT) == -ETIME) {
> > +	if (intel_gt_wait_for_idle(gt, I915_GT_SUSPEND_IDLE_TIMEOUT) == -ETIME)
> >   		/*
> >   		 * Forcibly cancel outstanding work and leave
> >   		 * the gpu quiet.
> >   		 */
> >   		intel_gt_set_wedged(gt);
> > -		intel_gt_retire_requests(gt);
> > -	}
> >   	intel_gt_pm_wait_for_idle(gt);
> > +
> > +	/* Make the GPU available again for swapout */
> > +	intel_gt_unset_wedged(gt);
> >   }
> >   void intel_gt_suspend_prepare(struct intel_gt *gt)