[Intel-gfx] [PATCH 2/2] drm/i915: Decouple the stuck pageflip on modeset

[Chris Wilson]

If we successfully confuse the hardware, and cause it to drop a queued
pageflip, we wait for 60s and issue a warning before continuing on with
the modeset. However, this leaves the pending pageflip still stuck
indefinitely. Pretend to userspace that it does complete, and let us
start afresh following the modeset.

v2: Rebase after refactor
v3: Rebase, rebase.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
References: https://bugs.freedesktop.org/show_bug.cgi?id=82612
---
 drivers/gpu/drm/i915/intel_display.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index ae5f0e3d18a1..842a5e1a8c8a 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -3434,9 +3434,19 @@ void intel_crtc_wait_for_pending_flips(struct drm_crtc *crtc)
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
 	WARN_ON(waitqueue_active(&dev_priv->pending_flip_queue));
-	WARN_ON(wait_event_timeout(dev_priv->pending_flip_queue,
-				   !intel_crtc_has_pending_flip(crtc),
-				   60*HZ) == 0);
+	if (WARN_ON(wait_event_timeout(dev_priv->pending_flip_queue,
+				       !intel_crtc_has_pending_flip(crtc),
+				       60*HZ) == 0)) {
+		struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
+		unsigned long flags;
+
+		spin_lock_irqsave(&dev->event_lock, flags);
+		if (intel_crtc->unpin_work) {
+			WARN_ONCE(1, "Removing stuck page flip\n");
+			page_flip_completed(intel_crtc);
+		}
+		spin_unlock_irqrestore(&dev->event_lock, flags);
+	}
 
 	if (crtc->primary->fb) {
 		mutex_lock(&dev->struct_mutex);
-- 
2.1.0