[v1] drm/msm/disp/dpu1: avoid perf update in frame done event

[v1] drm/msm/disp/dpu1: avoid perf update in frame done event

[Krishna Manikandan]

Crtc perf update from frame event work can result in
wrong bandwidth and clock update from dpu if the work
is scheduled after the swap state has happened.

Avoid such issues by moving perf update to complete
commit once the frame is accepted by the hardware.

Fixes: a29c8c024165 ("drm/msm/disp/dpu1: fix display underruns during modeset")
Signed-off-by: Krishna Manikandan <mkrishn@codeaurora.org>
---
 drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
index 18bc76b..4523d6b 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
@@ -407,9 +407,6 @@ static void dpu_crtc_frame_event_work(struct kthread_work *work)
 								fevent->event);
 		}
 
-		if (fevent->event & DPU_ENCODER_FRAME_EVENT_DONE)
-			dpu_core_perf_crtc_update(crtc, 0, false);
-
 		if (fevent->event & (DPU_ENCODER_FRAME_EVENT_DONE
 					| DPU_ENCODER_FRAME_EVENT_ERROR))
 			frame_done = true;
@@ -477,6 +474,7 @@ static void dpu_crtc_frame_event_cb(void *data, u32 event)
 void dpu_crtc_complete_commit(struct drm_crtc *crtc)
 {
 	trace_dpu_crtc_complete_commit(DRMID(crtc));
+	dpu_core_perf_crtc_update(crtc, 0, false);
 	_dpu_crtc_complete_flip(crtc);
 }
 
-- 
2.7.4

Re: [v1] drm/msm/disp/dpu1: avoid perf update in frame done event

[Doug Anderson]

Hi,

On Wed, May 26, 2021 at 10:08 PM Krishna Manikandan
<mkrishn@codeaurora.org> wrote:
>
> Crtc perf update from frame event work can result in
> wrong bandwidth and clock update from dpu if the work
> is scheduled after the swap state has happened.
>
> Avoid such issues by moving perf update to complete
> commit once the frame is accepted by the hardware.
>
> Fixes: a29c8c024165 ("drm/msm/disp/dpu1: fix display underruns during modeset")
> Signed-off-by: Krishna Manikandan <mkrishn@codeaurora.org>
> ---
>  drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)

I don't know much about this code or any of the theory behind it, but
I can confirm that this fixes the hang I was seeing with the previous
patch. On sc7180-trogdor-lazor:

Tested-by: Douglas Anderson <dianders@chromium.org>