linux-kernel - [RFC 2/3] drm/atomic: Call dma_fence_boost() when we've missed a vblank

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Date:   Wed, 19 May 2021 11:38:53 -0700
From:   Rob Clark <robdclark@...il.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     freedreno@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        Rob Clark <robdclark@...omium.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        linux-kernel@...r.kernel.org (open list)
Subject: [RFC 2/3] drm/atomic: Call dma_fence_boost() when we've missed a vblank

From: Rob Clark <robdclark@...omium.org>

Signed-off-by: Rob Clark <robdclark@...omium.org>
---
 drivers/gpu/drm/drm_atomic_helper.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 560aaecba31b..fe10fc2e7f86 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -1435,11 +1435,15 @@ int drm_atomic_helper_wait_for_fences(struct drm_device *dev,
 	int i, ret;
 
 	for_each_new_plane_in_state(state, plane, new_plane_state, i) {
+		u64 vblank_count;
+
 		if (!new_plane_state->fence)
 			continue;
 
 		WARN_ON(!new_plane_state->fb);
 
+		vblank_count = drm_crtc_vblank_count(new_plane_state->crtc);
+
 		/*
 		 * If waiting for fences pre-swap (ie: nonblock), userspace can
 		 * still interrupt the operation. Instead of blocking until the
@@ -1449,6 +1453,13 @@ int drm_atomic_helper_wait_for_fences(struct drm_device *dev,
 		if (ret)
 			return ret;
 
+		/*
+		 * Check if we've missed a vblank while waiting, and if we have
+		 * signal the fence that it's signaler should be boosted
+		 */
+		if (vblank_count != drm_crtc_vblank_count(new_plane_state->crtc))
+			dma_fence_boost(new_plane_state->fence);
+
 		dma_fence_put(new_plane_state->fence);
 		new_plane_state->fence = NULL;
 	}
-- 
2.30.2