drm/i915/gt: Only unwedge if we can reset first

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@linux.intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com> #v1
Link: https://patchwork.freedesktop.org/patch/msgid/20190927160335.10622-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/gt/intel_reset.c b/drivers/gpu/drm/i915/gt/intel_reset.c
index 76938fa..e189897 100644 (file)
--- a/drivers/gpu/drm/i915/gt/intel_reset.c
+++ b/drivers/gpu/drm/i915/gt/intel_reset.c
@@ -821,6 +821,7 @@ 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;
@@ -867,7 +868,12 @@ 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); /* XXX better agnosticism desired */
+       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