linux-kernel - Re: [PATCH] drm/tilcdc: send vblank event when disabling crtc

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Date:   Fri, 29 Jan 2021 09:58:33 +0200
From:   Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To:     quanyang.wang@...driver.com, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, Jyri Sarha <jyri.sarha@....fi>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Subject: Re: [PATCH] drm/tilcdc: send vblank event when disabling crtc

Dropped the @ti.com addresses and added the new ones.

 Tomi

On 29/01/2021 07:58, quanyang.wang@...driver.com wrote:
> From: Quanyang Wang <quanyang.wang@...driver.com>
> 
> When run xrandr to change resolution on Beaglebone Black board, it will
> print the error information:
> 
> root@...glebone:~# xrandr -display :0 --output HDMI-1 --mode 720x400
> [drm:drm_crtc_commit_wait] *ERROR* flip_done timed out
> [drm:drm_atomic_helper_wait_for_dependencies] *ERROR* [CRTC:32:tilcdc crtc] commit wait timed out
> [drm:drm_crtc_commit_wait] *ERROR* flip_done timed out
> [drm:drm_atomic_helper_wait_for_dependencies] *ERROR* [CONNECTOR:34:HDMI-A-1] commit wait timed out
> [drm:drm_crtc_commit_wait] *ERROR* flip_done timed out
> [drm:drm_atomic_helper_wait_for_dependencies] *ERROR* [PLANE:31:plane-0] commit wait timed out
> tilcdc 4830e000.lcdc: already pending page flip!
> 
> This is because there is operation sequence as below:
> 
> drm_atomic_connector_commit_dpms(mode is DRM_MODE_DPMS_OFF):
>     ...
>     drm_atomic_helper_setup_commit <- init_completion(commit_A->flip_done)
>     drm_atomic_helper_commit_tail
>         tilcdc_crtc_atomic_disable
>         tilcdc_plane_atomic_update <- drm_crtc_send_vblank_event in tilcdc_crtc_irq
>                                       is skipped since tilcdc_crtc->enabled is 0
>         tilcdc_crtc_atomic_flush   <- drm_crtc_send_vblank_event is skipped since
>                                       crtc->state->event is set to be NULL in
>                                       tilcdc_plane_atomic_update
> drm_mode_setcrtc:
>     ...
>     drm_atomic_helper_setup_commit <- init_completion(commit_B->flip_done)
>     drm_atomic_helper_wait_for_dependencies
>         drm_crtc_commit_wait   <- wait for commit_A->flip_done completing
> 
> Just as shown above, the steps which could complete commit_A->flip_done
> are all skipped and commit_A->flip_done will never be completed. This will
> result a time-out ERROR when drm_crtc_commit_wait check the commit_A->flip_done.
> So add drm_crtc_send_vblank_event in tilcdc_crtc_atomic_disable to
> complete commit_A->flip_done.
> 
> Fixes: cb345decb4d2 ("drm/tilcdc: Use standard drm_atomic_helper_commit")
> Signed-off-by: Quanyang Wang <quanyang.wang@...driver.com>
> ---
>  drivers/gpu/drm/tilcdc/tilcdc_crtc.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
> index 30213708fc99..d99afd19ca08 100644
> --- a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
> +++ b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
> @@ -515,6 +515,15 @@ static void tilcdc_crtc_off(struct drm_crtc *crtc, bool shutdown)
>  
>  	drm_crtc_vblank_off(crtc);
>  
> +	spin_lock_irq(&crtc->dev->event_lock);
> +
> +	if (crtc->state->event) {
> +		drm_crtc_send_vblank_event(crtc, crtc->state->event);
> +		crtc->state->event = NULL;
> +	}
> +
> +	spin_unlock_irq(&crtc->dev->event_lock);
> +
>  	tilcdc_crtc_disable_irqs(dev);
>  
>  	pm_runtime_put_sync(dev->dev);
>