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

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Date:   Tue, 9 Feb 2021 11:09:00 +0800
From:   "quanyang.wang" <quanyang.wang@...driver.com>
To:     Tomi Valkeinen <tomi.valkeinen@...asonboard.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
Subject: Re: [PATCH] drm/tilcdc: send vblank event when disabling crtc

Ping.

On 1/29/21 3:58 PM, Tomi Valkeinen wrote:
> 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);
>>