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

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Message-id: <542D3C96.7000400@samsung.com>
Date:	Thu, 02 Oct 2014 13:52:54 +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, Thierry Reding <treding@...dia.com>,
	Benjamin Gaignard <benjamin.gaignard@...aro.org>,
	Russell King <rmk+kernel@....linux.org.uk>,
	Daniel Vetter <daniel.vetter@...ll.ch>
Subject: Re: [PATCH] drm/exynos: fix vblank handling during dpms off

Hi,

+CC possible victims

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 .

This patch should break also other drivers, it seems at least following
drms could be affected:
armada, sti, tegra.

I guess after disabling and re-enabling crtc vblanks should stop
working, unless there are other bugs.

Regards
Andrzej

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