Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754759AbaJIKY0 (ORCPT ); Thu, 9 Oct 2014 06:24:26 -0400 Received: from mail-ig0-f169.google.com ([209.85.213.169]:44745 "EHLO mail-ig0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752853AbaJIKYO convert rfc822-to-8bit (ORCPT ); Thu, 9 Oct 2014 06:24:14 -0400 MIME-Version: 1.0 In-Reply-To: <20141009100811.GB3718@ulmo.nvidia.com> References: <542B9A0E.7020206@samsung.com> <1412151287-12845-1-git-send-email-a.hajda@samsung.com> <542D13CC.5000304@samsung.com> <542D2E7C.1020904@samsung.com> <542D3C96.7000400@samsung.com> <54362066.9000504@nvidia.com> <20141009100811.GB3718@ulmo.nvidia.com> From: Alexandre Courbot Date: Thu, 9 Oct 2014 19:23:52 +0900 Message-ID: Subject: Re: [PATCH] drm/exynos: fix vblank handling during dpms off To: Thierry Reding Cc: Alexandre Courbot , Andrzej Hajda , Inki Dae , Joonyoung Shim , "linux-samsung-soc@vger.kernel.org" , Daniel Vetter , Seung-Woo Kim , Linux Kernel Mailing List , "dri-devel@lists.freedesktop.org" , Kyungmin Park , Kukjin Kim , Benjamin Gaignard , Russell King , =?UTF-8?B?VmlsbGUgU3lyasOkbMOk?= , "linux-tegra@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 9, 2014 at 7:08 PM, Thierry Reding wrote: > On Thu, Oct 09, 2014 at 02:43:02PM +0900, Alexandre Courbot wrote: >> On 10/02/2014 08:52 PM, Andrzej Hajda wrote: >> >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. >> >> Indeed we (tegra) have just been hit by this. The problem seems to come from >> the fact that we have been using drm_vblank_pre_modeset, >> drm_vblank_post_modeset and drm_vblank_off conjointly. All these functions >> depend on the value of vblank->inmodeset, and 7ffd7a68511 increases the >> vblank reference counter only in drm_vblank_off, which can result in the >> acquired reference never being released. >> >> The following seems to fix this for Tegra, by stopping using >> drm_vblank_pre/post_modeset and relying on drm_vblank_off/on instead: >> >> diff --git a/drivers/gpu/drm/tegra/dc.c b/drivers/gpu/drm/tegra/dc.c >> index b08df07cad47..3955d81236d0 100644 >> --- a/drivers/gpu/drm/tegra/dc.c >> +++ b/drivers/gpu/drm/tegra/dc.c >> @@ -739,7 +739,6 @@ static const struct drm_crtc_funcs tegra_crtc_funcs = { >> >> static void tegra_crtc_disable(struct drm_crtc *crtc) >> { >> - struct tegra_dc *dc = to_tegra_dc(crtc); >> struct drm_device *drm = crtc->dev; >> struct drm_plane *plane; >> >> @@ -755,7 +754,7 @@ static void tegra_crtc_disable(struct drm_crtc *crtc) >> } >> } >> >> - drm_vblank_off(drm, dc->pipe); >> + drm_crtc_vblank_off(crtc); >> } >> >> static bool tegra_crtc_mode_fixup(struct drm_crtc *crtc, >> @@ -844,7 +843,7 @@ static int tegra_crtc_mode_set(struct drm_crtc *crtc, >> u32 value; >> int err; >> >> - drm_vblank_pre_modeset(crtc->dev, dc->pipe); >> + drm_crtc_vblank_off(crtc); >> >> err = tegra_crtc_setup_clk(crtc, mode); >> if (err) { >> @@ -946,7 +945,7 @@ static void tegra_crtc_commit(struct drm_crtc *crtc) >> value = GENERAL_ACT_REQ | WIN_A_ACT_REQ; >> tegra_dc_writel(dc, value, DC_CMD_STATE_CONTROL); >> >> - drm_vblank_post_modeset(crtc->dev, dc->pipe); >> + drm_crtc_vblank_on(crtc); >> } >> >> static void tegra_crtc_load_lut(struct drm_crtc *crtc) >> >> Thierry, does this look ok to you? > > Yes, that looks like almost the same patch that I sent out yesterday. > The difference is that I didn't replace the drm_vblank_pre_modeset() > call with drm_vblank_off() like you did, but rather just dropped the > former. > > I /think/ your version is more correct in that regard. Feel free to take that extra line in your patch then. ;) > > Thierry > >> But there might be another issue, which is that calls to drm_vblank_get() >> will return -EINVAL if invoked between drm_blank_off and drm_blank_on. Is >> this really the desired behavior? Can it at least happen? If so, how are >> drivers supposed to react to this situation? > > It shouldn't happen. If drm_vblank_off() and drm_vblank_on() are called > around a modeset they should never conflict with drm_vblank_get(), at > least on Tegra, because the modeset and page-flip IOCTLs will be > serialized. Ok, that's good. I was just wondering whether this case has been thought of. Actually, and seeing how drm_vblank_pre/post_modeset() have become useless (if not harmful), maybe it would be a good idea to come with a fixup patch that gets rid of them altogether and make their callers invoke drm_vblank_off/on() instead? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/