i915: wait for fence in mmio_flip_work_func

If a buffer is backed by dmabuf, wait on its reservation object's exclusive
fence before flipping.

v2: First commit
v3: Remove object_name_lock acquire
v4: Move wait ahead of mark_page_flip_active
    Use crtc->primary->fb to get GEM object instead of pending_flip_obj
    use_mmio_flip() return true when exclusive fence is attached
    Wait only on exclusive fences, interruptible with no timeout
v5: Move wait from do_mmio_flip to mmio_flip_work_func
    Style tweaks to more closely match rest of file
v6: Change back to unintteruptible wait to match __i915_wait_request due to
    inability to properly handle interrupted wait.
    Warn on error code from waiting.
v7: No change
v8: Test for !reservation_object_signaled_rcu(test_all=FALSE) instead of
    obj->base.dma_buf->resv->fence_excl

Link: https://patchwork.kernel.org/patch/7704181/Signed-off-by: Alex Goins <agoins@nvidia.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

drivers/gpu/drm/i915/intel_display.c

@@ -44,6 +44,8 @@
 #include <drm/drm_plane_helper.h>
 #include <drm/drm_rect.h>
 #include <linux/dma_remapping.h>
+#include <linux/reservation.h>
+#include <linux/dma-buf.h>
 
 /* Primary plane formats for gen <= 3 */
 static const uint32_t i8xx_primary_formats[] = {
@@ -11204,6 +11206,10 @@ static bool use_mmio_flip(struct intel_engine_cs *ring,
 		return true;
 	else if (i915.enable_execlists)
 		return true;
+	else if (obj->base.dma_buf &&
+		 !reservation_object_test_signaled_rcu(obj->base.dma_buf->resv,
+						       false))
+		return true;
 	else
 		return ring != i915_gem_request_get_ring(obj->last_write_req);
 }
@@ -11318,6 +11324,9 @@ static void intel_mmio_flip_work_func(struct work_struct *work)
 {
 	struct intel_mmio_flip *mmio_flip =
 		container_of(work, struct intel_mmio_flip, work);
+	struct intel_framebuffer *intel_fb =
+		to_intel_framebuffer(mmio_flip->crtc->base.primary->fb);
+	struct drm_i915_gem_object *obj = intel_fb->obj;
 
 	if (mmio_flip->req) {
 		WARN_ON(__i915_wait_request(mmio_flip->req,
@@ -11327,6 +11336,12 @@ static void intel_mmio_flip_work_func(struct work_struct *work)
 		i915_gem_request_unreference__unlocked(mmio_flip->req);
 	}
 
+	/* For framebuffer backed by dmabuf, wait for fence */
+	if (obj->base.dma_buf)
+		WARN_ON(reservation_object_wait_timeout_rcu(obj->base.dma_buf->resv,
+							    false, false,
+							    MAX_SCHEDULE_TIMEOUT) < 0);
+
 	intel_do_mmio_flip(mmio_flip);
 	kfree(mmio_flip);
 }