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Date:   Tue, 09 Feb 2021 23:38:01 +0200
From:   Jyri Sarha <jyri.sarha@iki.fi>
To:     quanyang.wang@windriver.com
Cc:     Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
Subject: Re: [RESEND][PATCH] drm/tilcdc: send vblank event when disabling crtc
In-Reply-To: <20210209082415.382602-1-quanyang.wang@windriver.com>
References: <20210209082415.382602-1-quanyang.wang@windriver.com>
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On 2021-02-09 10:24, quanyang.wang@windriver.com wrote:
> From: Quanyang Wang <quanyang.wang@windriver.com>
> 
> When run xrandr to change resolution on Beaglebone Black board, it will
> print the error information:
> 
> root@beaglebone:~# 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@windriver.com>

Reviewed-by: Jyri Sarha <jyri.sarha@iki.fi>
Tested-by: Jyri Sarha <jyri.sarha@iki.fi>

Thanks a lot! I think I have bumbed into this once or twice, but latelu 
I have had time to look into this. I'll merge this to drm-misc-next 
soon.

Best regards,
Jyri

> ---
>  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);