linux-kernel - [PATCH 2/5] drm/nouveau/kms/nv50-: Check vbl count after CRC context flip

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Date:   Mon, 18 Jan 2021 20:48:46 -0500
From:   Lyude Paul <lyude@...hat.com>
To:     nouveau@...ts.freedesktop.org
Cc:     Martin Peres <martin.peres@...e.fr>,
        Jeremy Cline <jcline@...hat.com>,
        Simon Ser <contact@...rsion.fr>,
        Ben Skeggs <bskeggs@...hat.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Dave Airlie <airlied@...il.com>,
        dri-devel@...ts.freedesktop.org (open list:DRM DRIVER FOR NVIDIA
        GEFORCE/QUADRO GPUS), linux-kernel@...r.kernel.org (open list)
Subject: [PATCH 2/5] drm/nouveau/kms/nv50-: Check vbl count after CRC context flip

While I haven't seen us take too long in nv50_crc_ctx_flip_work() outside of
users with kernel logging on a serial port, it probably would be a good idea to
check how long we take just in case we need to go faster in the future.

Cc: Martin Peres <martin.peres@...e.fr>
Cc: Jeremy Cline <jcline@...hat.com>
Cc: Simon Ser <contact@...rsion.fr>
Signed-off-by: Lyude Paul <lyude@...hat.com>
---
 drivers/gpu/drm/nouveau/dispnv50/crc.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/dispnv50/crc.c b/drivers/gpu/drm/nouveau/dispnv50/crc.c
index 3c50b29a37ff..ef942248345c 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/crc.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/crc.c
@@ -86,6 +86,8 @@ static void nv50_crc_ctx_flip_work(struct kthread_work *base)
 	struct drm_crtc *crtc = &head->base.base;
 	struct drm_device *dev = crtc->dev;
 	struct nv50_disp *disp = nv50_disp(dev);
+	const uint64_t start_vbl = drm_crtc_vblank_count(crtc);
+	uint64_t end_vbl;
 	u8 new_idx = crc->ctx_idx ^ 1;
 
 	/*
@@ -94,9 +96,7 @@ static void nv50_crc_ctx_flip_work(struct kthread_work *base)
 	 */
 	if (!mutex_trylock(&disp->mutex)) {
 		drm_dbg_kms(dev, "Lock contended, delaying CRC ctx flip for %s\n", crtc->name);
-		drm_vblank_work_schedule(work,
-					 drm_crtc_vblank_count(crtc) + 1,
-					 true);
+		drm_vblank_work_schedule(work, start_vbl + 1, true);
 		return;
 	}
 
@@ -107,6 +107,12 @@ static void nv50_crc_ctx_flip_work(struct kthread_work *base)
 	nv50_crc_program_ctx(head, &crc->ctx[new_idx]);
 	mutex_unlock(&disp->mutex);
 
+	end_vbl = drm_crtc_vblank_count(crtc);
+	if (unlikely(end_vbl != start_vbl))
+		NV_ERROR(nouveau_drm(dev),
+			 "Failed to flip CRC context on %s on time (%llu > %llu)\n",
+			 crtc->name, end_vbl, start_vbl);
+
 	spin_lock_irq(&crc->lock);
 	crc->ctx_changed = true;
 	spin_unlock_irq(&crc->lock);
-- 
2.29.2