Re: [PATCH v2] drm/msm/dpu: make "vblank timeout" more useful

From: Abhinav Kumar
Date: Wed Feb 14 2024 - 13:34:05 EST

On 2/8/2024 6:50 AM, Dmitry Baryshkov wrote:
We have several reports of vblank timeout messages. However after some
debugging it was found that there might be different causes to that.
To allow us to identify the DPU block that gets stuck, include the
actual CTL_FLUSH value into the timeout message and trigger the devcore
snapshot capture.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
Changes in v2:
- Added a call to msm_disp_snapshot_state() to trigger devcore dump
- Link to v1:
drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c
index d0f56c5c4cce..a8d6165b3c0a 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c
@@ -489,7 +489,8 @@ static int dpu_encoder_phys_vid_wait_for_commit_done(
(hw_ctl->ops.get_flush_register(hw_ctl) == 0),
if (ret <= 0) {
- DPU_ERROR("vblank timeout\n");
+ DPU_ERROR("vblank timeout: %x\n", hw_ctl->ops.get_flush_register(hw_ctl));
+ msm_disp_snapshot_state(phys_enc->parent->dev);

There is no rate limiting in this piece of code unfortunately. So this will flood the number of snapshots.

Short-term solution is you can go with a vblank_timeout_cnt and reset it in the enable() like other similar error counters.

long-term solution is we need to centralize these error locations to one single dpu_encoder_error_handler() with a single counter and the error handler will print out the error code along with the snapshot instead of the snapshot being called from all over the place.

return -ETIMEDOUT;

base-commit: 39676dfe52331dba909c617f213fdb21015c8d10
change-id: 20240106-fd-dpu-debug-timeout-e917f0bc8063

Best regards,