Re: [Intel-gfx] [PATCH 2/2] drm/i915/gt: Only unwedge if we can reset first

[Daniele Ceraolo Spurio]

On 9/9/19 3:55 PM, Chris Wilson wrote:
Unwedging the GPU requires a successful GPU reset before we restore the
default submission, or else we may see residual context switch events
that we were not expecting.

Reported-by: Janusz Krzysztofik <janusz.krzyszto...@linux.intel.com>
Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
Cc: Janusz Krzysztofik <janusz.krzyszto...@linux.intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospu...@intel.com>
---
  drivers/gpu/drm/i915/gt/intel_reset.c | 7 ++++++-
  1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_reset.c 
b/drivers/gpu/drm/i915/gt/intel_reset.c
index fe57296b790c..5242496a893a 100644
--- a/drivers/gpu/drm/i915/gt/intel_reset.c
+++ b/drivers/gpu/drm/i915/gt/intel_reset.c
@@ -809,6 +809,7 @@ static bool __intel_gt_unset_wedged(struct intel_gt *gt)
        struct intel_gt_timelines *timelines = &gt->timelines;
        struct intel_timeline *tl;
        unsigned long flags;
+       bool ok;
  
  	if (!test_bit(I915_WEDGED, &gt->reset.flags))
                return true;
@@ -854,7 +855,11 @@ static bool __intel_gt_unset_wedged(struct intel_gt *gt)
        }
        spin_unlock_irqrestore(&timelines->lock, flags);
  
-	intel_gt_sanitize(gt, false);
+       ok = false;
+       if (!reset_clobbers_display(gt->i915))
+               ok = __intel_gt_reset(gt, ALL_ENGINES) == 0;

Of the thing we had in the gt_sanitize, we're ok skipping the 
uc_sanitize() because we take care of that during wedge (from 
intel_uc_reset_prepare), but what about the loop of 
__intel_engine_reset()? Is that safe to skip here?

Apart from that, the patch LGTM. Worth noting that with this change a 
successful reset is required to unwedge even after a suspend/resume 
cycle (in gem_sanitize), which is a good thing IMO.

Daniele

+       if (!ok)
+               return false;
  
  	/*
         * Undo nop_submit_request. We prevent all new i915 requests from

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