[v1] drm/msm/disp/dpu1: fix display underruns during modeset.

[v1] drm/msm/disp/dpu1: fix display underruns during modeset.

[Kalyan Thota]

During crtc disable, display perf structures are reset to 0
which includes state varibles which are immutable. On crtc
enable, we use the same structures and they don't refelect
the actual values

1) Fix is to avoid updating the state structures during disable.
2) Reset the perf structures during atomic check when there is no
modeset enable.

Signed-off-by: Kalyan Thota <kalyan_t@codeaurora.org>
---
 drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.c | 1 -
 drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c      | 1 +
 2 files changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.c
index 37c8270..b4cd479 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.c
@@ -382,7 +382,6 @@ int dpu_core_perf_crtc_update(struct drm_crtc *crtc,
 	} else {
 		DPU_DEBUG("crtc=%d disable\n", crtc->base.id);
 		memset(old, 0, sizeof(*old));
-		memset(new, 0, sizeof(*new));
 		update_bus = true;
 		update_clk = true;
 	}
diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
index 9a80981..a821e2c 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
@@ -912,6 +912,7 @@ static int dpu_crtc_atomic_check(struct drm_crtc *crtc,
 	if (!state->enable || !state->active) {
 		DPU_DEBUG("crtc%d -> enable %d, active %d, skip atomic_check\n",
 				crtc->base.id, state->enable, state->active);
+		memset(&cstate->new_perf, 0, sizeof(cstate->new_perf));
 		goto end;
 	}
 
-- 
2.7.4

Re: [v1] drm/msm/disp/dpu1: fix display underruns during modeset.

[Doug Anderson]

Hi,

On Fri, Mar 19, 2021 at 5:54 AM Kalyan Thota <kalyan_t@codeaurora.org> wrote:
>
> During crtc disable, display perf structures are reset to 0
> which includes state varibles which are immutable. On crtc
> enable, we use the same structures and they don't refelect
> the actual values
>
> 1) Fix is to avoid updating the state structures during disable.
> 2) Reset the perf structures during atomic check when there is no
> modeset enable.
>
> Signed-off-by: Kalyan Thota <kalyan_t@codeaurora.org>
> ---
>  drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.c | 1 -
>  drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c      | 1 +
>  2 files changed, 1 insertion(+), 1 deletion(-)

I think Stephen was the one who originally noticed this and reported it, so:

Reported-by: Stephen Boyd <swboyd@chromium.org>

Seems to work for me. I got into the state where it was doing a
modeset at reboot (could see the underflow color for a period of time
when this happened). I added your patch and it looks better.

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