linux-kernel - Re: [PATCH] drm/exynos: fix vblank handling during dpms off

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Date:	Fri, 10 Oct 2014 14:39:54 +0200
From:	Andrzej Hajda <a.hajda@...sung.com>
To:	Inki Dae <inki.dae@...sung.com>,
	Joonyoung Shim <jy0922.shim@...sung.com>
Cc:	Seung-Woo Kim <sw0312.kim@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	David Airlie <airlied@...ux.ie>,
	Kukjin Kim <kgene.kim@...sung.com>,
	dri-devel@...ts.freedesktop.org, linux-samsung-soc@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/exynos: fix vblank handling during dpms off

On 10/02/2014 12:52 PM, Inki Dae wrote:
> On 2014년 10월 02일 17:58, Joonyoung Shim wrote:
>> Hi Andrzej,
>>
>> On 10/01/2014 05:14 PM, Andrzej Hajda wrote:
>>> The patch disables vblanks during dpms off only if pagefilp has
>>> not been finished. It also replaces drm_vblank_off with drm_crtc_vblank_put.
>>> It fixes issue with page_flip ioctl not being able to acquire vblank counter.
>> This problem isn't related with pageflip, it just causes from
>> 7ffd7a68511c710b84db3548a1997fd2625f580a commit (drm: Always reject
>> drm_vblank_get() after drm_vblank_off()).
>>
>> We need to use drm_vblank_on() as a counterpart to drm_vblank_off()
>> after the commit .
>>
>> How about below patch?
> Thanks you Joonyoung and Andrzej,
>
> drm_vblank_on/off() are legacy api so it would be better to use
> drm_vblank_crtc_on/off functions instead.
>
> And drm_vblank_crtc_off() makes sure that the latest vblank frame count
> is stored and restored by drm_vblank_crtc_on() again. So my opinion is,
>
> static void exynos_drm_crtc_dpms(struct drm_crtc *crtc, int mode)
> {
> 	[snip]
>
> 	if (mode > DRM_MODE_DPMS_ON) {
> 		/* wait for the completion of page flip. */
> 		if (!wait_event_timeout(exynos_crtc->pending_flip_queue,
> 				!atomic_read(&exynos_crtc->pending_flip),
> 				HZ/20))
> 			atomic_set(&exynos_crtc->pending_flip, 0);
> 		drm_crtc_vblank_off(crtc);		//<- store the latest vblank frame count.
> 	} else {
> 		drm_crtc_vblank_on(crtc);		//<- restore the vblank frame count.
> 	}
>
> 	[snip]
> }
>
>
> Tested and worked well with above patch. How about it?
>
>

drm_crtc_vblank_on should be called after dpms on, otherwise it can fail enabling vblank. I have provided
full explanation in my other email [1].
You can modify your patch or just use the one provided in [1].

[1]: http://permalink.gmane.org/gmane.comp.video.dri.devel/116152

Regards
Andrzej

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