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From:   Stephen Boyd <swboyd@chromium.org>
To:     Rob Clark <robdclark@gmail.com>,
        Abhinav Kumar <quic_abhinavk@quicinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Cc:     linux-kernel@vger.kernel.org, patches@lists.linux.dev,
        Sean Paul <sean@poorly.run>, dri-devel@lists.freedesktop.org,
        freedreno@lists.freedesktop.org,
        Mark Yacoub <markyacoub@chromium.org>,
        Jessica Zhang <quic_jesszhan@quicinc.com>
Subject: [PATCH] drm/msm/dpu: Increment vsync_cnt before waking up userspace
Date:   Tue, 21 Jun 2022 19:38:55 -0700
Message-Id: <20220622023855.2970913-1-swboyd@chromium.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

The 'vsync_cnt' is used to count the number of frames for a crtc.
Unfortunately, we increment the count after waking up userspace via
dpu_crtc_vblank_callback() calling drm_crtc_handle_vblank().
drm_crtc_handle_vblank() wakes up userspace processes that have called
drm_wait_vblank_ioctl(), and if that ioctl is expecting the count to
increase it won't.

Increment the count before calling into the drm APIs so that we don't
have to worry about ordering the increment with anything else in drm.
This fixes a software video decode test that fails to see frame counts
increase on Trogdor boards.

Cc: Mark Yacoub <markyacoub@chromium.org>
Cc: Jessica Zhang <quic_jesszhan@quicinc.com>
Fixes: 885455d6bf82 ("drm/msm: Change dpu_crtc_get_vblank_counter to use vsync count.")
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
---
 drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
index 3a462e327e0e..a1b8c4592943 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
@@ -1251,12 +1251,13 @@ static void dpu_encoder_vblank_callback(struct drm_encoder *drm_enc,
 	DPU_ATRACE_BEGIN("encoder_vblank_callback");
 	dpu_enc = to_dpu_encoder_virt(drm_enc);
 
+	atomic_inc(&phy_enc->vsync_cnt);
+
 	spin_lock_irqsave(&dpu_enc->enc_spinlock, lock_flags);
 	if (dpu_enc->crtc)
 		dpu_crtc_vblank_callback(dpu_enc->crtc);
 	spin_unlock_irqrestore(&dpu_enc->enc_spinlock, lock_flags);
 
-	atomic_inc(&phy_enc->vsync_cnt);
 	DPU_ATRACE_END("encoder_vblank_callback");
 }
 

base-commit: f2906aa863381afb0015a9eb7fefad885d4e5a56
-- 
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