From mboxrd@z Thu Jan 1 00:00:00 1970 From: Inki Dae Subject: Re: [PATCH 5/9] drm/exynos/crtc: fix framebuffer reference sequence Date: Fri, 12 Sep 2014 20:24:41 +0900 Message-ID: <5412D7F9.4080600@samsung.com> References: <1410268573-2297-1-git-send-email-a.hajda@samsung.com> <1410268573-2297-6-git-send-email-a.hajda@samsung.com> <5412B02A.6040609@samsung.com> <20140912085710.GD4740@phenom.ffwll.local> <5412BC8D.2030007@samsung.com> <5412CEDF.7030806@samsung.com> <5412D353.8080007@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mailout1.samsung.com ([203.254.224.24]:37022 "EHLO mailout1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752638AbaILLYo (ORCPT ); Fri, 12 Sep 2014 07:24:44 -0400 In-reply-to: <5412D353.8080007@samsung.com> Sender: linux-samsung-soc-owner@vger.kernel.org List-Id: linux-samsung-soc@vger.kernel.org To: Andrzej Hajda Cc: "moderated list:ARM/S5P EXYNOS AR..." , Seung-Woo Kim , open list , dri-devel@lists.freedesktop.org, Kyungmin Park , Marek Szyprowski On 2014=EB=85=84 09=EC=9B=94 12=EC=9D=BC 20:04, Andrzej Hajda wrote: > On 09/12/2014 12:45 PM, Inki Dae wrote: >> On 2014=EB=85=84 09=EC=9B=94 12=EC=9D=BC 18:27, Andrzej Hajda wrote: >>> On 09/12/2014 10:57 AM, Daniel Vetter wrote: >>>> On Fri, Sep 12, 2014 at 05:34:50PM +0900, Inki Dae wrote: >>>>> Hi Andrzej, >>>>> >>>>> On 2014=EB=85=84 09=EC=9B=94 09=EC=9D=BC 22:16, Andrzej Hajda wro= te: >>>>>> Adding reference to framebuffer should be accompanied with remov= ing >>>>>> reference to old framebuffer assigned to the plane. >>>>>> This patch removes following warning: >>>>>> >>>>>> [ 95.038017] WARNING: CPU: 1 PID: 3067 at drivers/gpu/drm/drm_= crtc.c:5115 drm_mode_config_cleanup+0x258/0x268() >>>>>> [ 95.048086] Modules linked in: >>>>>> [ 95.051430] CPU: 1 PID: 3067 Comm: bash Tainted: G W = 3.16.0-11355-g7a6eca5-dirty #3015 >>>>>> [ 95.060058] [] (unwind_backtrace) from []= (show_stack+0x10/0x14) >>>>>> [ 95.067766] [] (show_stack) from [] (dump= _stack+0x70/0xbc) >>>>>> [ 95.074953] [] (dump_stack) from [] (warn= _slowpath_common+0x64/0x88) >>>>>> [ 95.083005] [] (warn_slowpath_common) from [] (warn_slowpath_null+0x1c/0x24) >>>>>> [ 95.091780] [] (warn_slowpath_null) from [] (drm_mode_config_cleanup+0x258/0x268) >>>>>> [ 95.100983] [] (drm_mode_config_cleanup) from [] (exynos_drm_unload+0x38/0x50) >>>>>> [ 95.109915] [] (exynos_drm_unload) from [= ] (drm_dev_unregister+0x24/0x98) >>>>>> [ 95.118414] [] (drm_dev_unregister) from [] (drm_put_dev+0x28/0x64) >>>>>> [ 95.126412] [] (drm_put_dev) from [] (tak= e_down_master+0x24/0x44) >>>>>> [ 95.134218] [] (take_down_master) from []= (component_del+0x8c/0xc8) >>>>>> [ 95.142201] [] (component_del) from [] (e= xynos_dsi_remove+0x18/0x2c) >>>>>> [ 95.150294] [] (exynos_dsi_remove) from [= ] (platform_drv_remove+0x18/0x1c) >>>>>> [ 95.158872] [] (platform_drv_remove) from [] (__device_release_driver+0x70/0xc4) >>>>>> [ 95.167981] [] (__device_release_driver) from [] (device_release_driver+0x20/0x2c) >>>>>> [ 95.177268] [] (device_release_driver) from [] (unbind_store+0x5c/0x94) >>>>>> [ 95.185597] [] (unbind_store) from [] (dr= v_attr_store+0x20/0x2c) >>>>>> [ 95.193323] [] (drv_attr_store) from [] (= sysfs_kf_write+0x4c/0x50) >>>>>> [ 95.201224] [] (sysfs_kf_write) from [] (= kernfs_fop_write+0xc4/0x184) >>>>>> [ 95.209393] [] (kernfs_fop_write) from []= (vfs_write+0xa0/0x1a8) >>>>>> [ 95.217111] [] (vfs_write) from [] (SyS_w= rite+0x40/0x8c) >>>>>> [ 95.224146] [] (SyS_write) from [] (ret_f= ast_syscall+0x0/0x48) >>>>>> >>>>>> Signed-off-by: Andrzej Hajda >>>>>> --- >>>>>> drivers/gpu/drm/exynos/exynos_drm_crtc.c | 6 ++++++ >>>>>> 1 file changed, 6 insertions(+) >>>>>> >>>>>> diff --git a/drivers/gpu/drm/exynos/exynos_drm_crtc.c b/drivers/= gpu/drm/exynos/exynos_drm_crtc.c >>>>>> index b68e58f..bde19f4 100644 >>>>>> --- a/drivers/gpu/drm/exynos/exynos_drm_crtc.c >>>>>> +++ b/drivers/gpu/drm/exynos/exynos_drm_crtc.c >>>>>> @@ -145,10 +145,16 @@ exynos_drm_crtc_mode_set(struct drm_crtc *= crtc, struct drm_display_mode *mode, >>>>>> if (ret) >>>>>> return ret; >>>>>> =20 >>>>>> + /* we need to unreference current fb after replacing it with n= ew one */ >>>>>> + old_fb =3D plane->fb; >>>>>> + >>>>>> plane->crtc =3D crtc; >>>>>> plane->fb =3D crtc->primary->fb; >>>>>> drm_framebuffer_reference(plane->fb); >>>>>> =20 >>>>>> + if (old_fb) >>>>>> + drm_framebuffer_unreference(old_fb); >>>>> This time would be a good chance that we can consider drm flip qu= eue to >>>>> make sure that whole memory region to old_fb is scanned out compl= etely >>>>> before dropping a reference of old_fb. the reference of old_fb sh= ould be >>>>> dropped at irq handler of each crtc devices, fimd and mixer. >>>> Generally it's not a good idea to drop fb references from irq cont= ext, >>>> since if you actually drop the last reference it'll blow up: fb cl= eanup >>>> needs a bunch of mutexes. >>> I agree with that. >>> >>>> Also the drm core really should be taking care of this for you, yo= u only >>>> need to grab references yourself for async flips if you want the b= uffer to >>>> survive a bit. crtc_mode_set has not need for this. I expect that = the >>>> refcounting bug is somewhere else, at least from my experience cha= sing >>>> such issues in i915 ;-) >>> Hmm, maybe I miss something but I do not see the core grabbing fb r= eference >>> on plane->fb update. On the other side drm_framebuffer_remove calls >>> drm_plane_force_disable which drops plane->fb reference. >>> I am not yet familiar with this code so maybe there is better solut= ion. >>> >>> If not I guess it would be better to move this code to >>> exynos_plane_mode_set. >>> At least it is done this way in omap and msm, in fact it seems bett= er place >> I cannot see it in msm. In case of msm, drm flip queue is used in >> mdp4/5_crtc_mode_set function. See update_fb function there. >=20 > fb reference dance for planes is in mdp*_plane_update. >=20 > Regarding drm flip in msm old fb unreferencing is done via > drm_flip_work_queue. Yes, that is what drm flip queue does and I mentioned earlier below, http://www.mail-archive.com/linux-kernel@vger.kernel.org/msg724161.html I think we have a talk about how we have to drop a reference to old_fb. Thanks, Inki Dae >=20 > Regards > Andrzej >=20 >> >>> for such things. What do you think? >>> >>> Regards >>> Andrzej >>> >>>> -Daniel >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-sam= sung-soc" in >>> the body of a message to majordomo@vger.kernel.org >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>> >> >=20 > -- > To unsubscribe from this list: send the line "unsubscribe linux-samsu= ng-soc" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >=20