drm/i915: Convert mmio_flip::seqno to struct request

Converted the mmio_flip 'seqno' value to be a request structure as part of the
on going seqno to request changes. This includes reference counting the request
being saved away to ensure it can not be retired and freed while the flip code
is still waiting on it.

v2: Used the IRQ friendly request dereference call in the notify handler as that
code is called asynchronously without holding any useful mutex locks.

For: VIZ-4377
Signed-off-by: NJohn Harrison <John.C.Harrison@Intel.com>
Reviewed-by: NThomas Daniel <Thomas.Daniel@intel.com>
[danvet: Drop the _irq variant and use the normal reques unref,
wrapped in dev->struct_mutex per the discussion on the m-l.]
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -9612,20 +9612,24 @@ static void intel_do_mmio_flip(struct intel_crtc *intel_crtc)
 
 static void intel_mmio_flip_work_func(struct work_struct *work)
 {
-	struct intel_crtc *intel_crtc =
+	struct intel_crtc *crtc =
 		container_of(work, struct intel_crtc, mmio_flip.work);
-	struct intel_engine_cs *ring;
-	uint32_t seqno;
+	struct intel_mmio_flip *mmio_flip;
 
-	seqno = intel_crtc->mmio_flip.seqno;
-	ring = intel_crtc->mmio_flip.ring;
-
-	if (seqno)
-		WARN_ON(__i915_wait_seqno(ring, seqno,
-					  intel_crtc->reset_counter,
+	mmio_flip = &crtc->mmio_flip;
+	if (mmio_flip->req)
+		WARN_ON(__i915_wait_seqno(i915_gem_request_get_ring(mmio_flip->req),
+					  i915_gem_request_get_seqno(mmio_flip->req),
+					  crtc->reset_counter,
 					  false, NULL, NULL) != 0);
 
-	intel_do_mmio_flip(intel_crtc);
+	intel_do_mmio_flip(crtc);
+	if (mmio_flip->req) {
+		mutex_lock(&crtc->base.dev->struct_mutex);
+		i915_gem_request_unreference(mmio_flip->req);
+		mutex_unlock(&crtc->base.dev->struct_mutex);
+	}
+	mmio_flip->req = NULL;
 }
 
 static int intel_queue_mmio_flip(struct drm_device *dev,
@@ -9637,9 +9641,8 @@ static int intel_queue_mmio_flip(struct drm_device *dev,
 {
 	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
 
-	intel_crtc->mmio_flip.seqno =
-			     i915_gem_request_get_seqno(obj->last_write_req);
-	intel_crtc->mmio_flip.ring = obj->ring;
+	i915_gem_request_assign(&intel_crtc->mmio_flip.req,
+				obj->last_write_req);
 
 	schedule_work(&intel_crtc->mmio_flip.work);
 

drivers/gpu/drm/i915/intel_drv.h

@@ -406,8 +406,7 @@ struct intel_pipe_wm {
 };
 
 struct intel_mmio_flip {
-	u32 seqno;
-	struct intel_engine_cs *ring;
+	struct drm_i915_gem_request *req;
 	struct work_struct work;
 };