drm/i915: Skip an engine reset if it recovered before our preparations

At the beginning of a reset, we disable the submission method and find
the stuck request. We expect to find a stuck request for we have
declared the engine stalled. However, if we find no active request, the
engine must have recovered from its stall before we could issue a reset,
so let the engine continue on without a reset. If the engine is truly
stuck, we will back soon enough with the next reset attempt.

v2: Remove the stale debug message.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michel Thierry <michel.thierry@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Michel Thierry <michel.thierry@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171216002206.31737-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index ca9f4b2862eb80a2825e279554ddf2857d146492..6d39fdf2b604bf8436020be939907b09cdacf237 100644 (file)
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -2011,19 +2011,19 @@ int i915_reset_engine(struct intel_engine_cs *engine, unsigned int flags)
 
        GEM_BUG_ON(!test_bit(I915_RESET_ENGINE + engine->id, &error->flags));
 
+       active_request = i915_gem_reset_prepare_engine(engine);
+       if (IS_ERR_OR_NULL(active_request)) {
+               /* Either the previous reset failed, or we pardon the reset. */
+               ret = PTR_ERR(active_request);
+               goto out;
+       }
+
        if (!(flags & I915_RESET_QUIET)) {
                dev_notice(engine->i915->drm.dev,
                           "Resetting %s after gpu hang\n", engine->name);
        }
        error->reset_engine_count[engine->id]++;
 
-       active_request = i915_gem_reset_prepare_engine(engine);
-       if (IS_ERR(active_request)) {
-               DRM_DEBUG_DRIVER("Previous reset failed, promote to full reset\n");
-               ret = PTR_ERR(active_request);
-               goto out;
-       }
-
        if (!engine->i915->guc.execbuf_client)
                ret = intel_gt_reset_engine(engine->i915, engine);
        else