[PATCH 01/30] drm/i915/gt: Only unwedge if we can reset first

[Chris Wilson]

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.

v2: Pull in the special-case reset_clobbers_display, and explain why it
should be safe in the context of unwedging.

v3: Just forget all about resets before unwedging if it will clobber the
display; risk it all.

Reported-by: Janusz Krzysztofik <janusz.krzysztofik at linux.intel.com>
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Janusz Krzysztofik <janusz.krzysztofik at linux.intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com> #v1
---
 drivers/gpu/drm/i915/gt/intel_reset.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_reset.c b/drivers/gpu/drm/i915/gt/intel_reset.c
index d08226f5bea5..11781a626f75 100644
--- a/drivers/gpu/drm/i915/gt/intel_reset.c
+++ b/drivers/gpu/drm/i915/gt/intel_reset.c
@@ -807,6 +807,7 @@ 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;
@@ -853,7 +854,12 @@ static bool __intel_gt_unset_wedged(struct intel_gt *gt)
 	}
 	spin_unlock_irqrestore(&timelines->lock, flags);
 
-	intel_gt_sanitize(gt, false);
+	/* We must reset pending GPU events before restoring our submission */
+	ok = !HAS_EXECLISTS(gt->i915);
+	if (!INTEL_INFO(gt->i915)->gpu_reset_clobbers_display)
+		ok = __intel_gt_reset(gt, ALL_ENGINES) == 0;
+	if (!ok)
+		return false;
 
 	/*
 	 * Undo nop_submit_request. We prevent all new i915 requests from
-- 
2.23.0