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[84.1.223.139]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-435e131cf16sm6937398f8f.22.2026.01.28.04.14.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Jan 2026 04:14:59 -0800 (PST) From: Timur =?UTF-8?B?S3Jpc3TDs2Y=?= To: Christian =?UTF-8?B?S8O2bmln?= , Alex Deucher , Hamza Mahfooz , Michel =?UTF-8?B?RMOkbnplcg==?= Cc: Mario Limonciello , dri-devel@lists.freedesktop.org, Alex Deucher , David Airlie , Simona Vetter , Harry Wentland , Leo Li , Rodrigo Siqueira , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Sunil Khatri , Ce Sun , Lijo Lazar , Kenneth Feng , Ivan Lipski , Alex Hung , Tom Chung , Melissa Wen , Michel =?UTF-8?B?RMOkbnplcg==?= , Fangzhi Zuo , amd-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] drm: introduce page_flip_timeout() Date: Wed, 28 Jan 2026 13:14:58 +0100 Message-ID: <2203806.9o76ZdvQCi@timur-hyperion> In-Reply-To: References: <20260123000537.2450496-1-someguy@effective-light.com> <17cd6378-e3fa-419b-90d3-7e0549817110@amd.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" On Wednesday, January 28, 2026 12:26:20=E2=80=AFPM Central European Standar= d Time=20 Michel D=C3=A4nzer wrote: > On 1/28/26 11:39, Christian K=C3=B6nig wrote: > > On 1/27/26 23:57, Alex Deucher wrote: > >> On Tue, Jan 27, 2026 at 5:53=E2=80=AFPM Hamza Mahfooz > >>=20 > >> wrote: > >>> On Mon, Jan 26, 2026 at 09:20:55AM -0500, Alex Deucher wrote: > >>>> I suspect just calling drm_crtc_send_vblank_event() here on the > >>>> relevant crtcs would be enough. > >>>=20 > >>> Seems like an interesting idea, though I would imagine we would still > >>> want to attempt a reset (of some kind) assuming that the subsequent p= age > >>> flip also experiences a timeout. > >>=20 > >> Is it actually a timeout or just missed interrupts? I'm wondering if > >> some power feature races with the modeset and causes the interrupt to > >> get missed from time to time. > >=20 > > That is my strong suspicion as well. > >=20 > > Even if we missed a vblank interrupt that thing is reoccurring, so the > > worst thing that can happen is that we delayed reporting back success by > > one frame. > >=20 > > So something must have turned the CRTC fully off. >=20 > Not sure that's a generally valid conclusion (do the gitlab issues talk > about the display going black, or about it staying on but freezing?). In all the bug reports I've seen about page flip timeouts, and in all the=20 timeouts I've seen on my machine, the screen remains on, but frozen. It doesn't go black and doesn't turn off. Christian, why would the CRTC be turned off? > AFAIR > at least in some cases amdgpu uses a dedicated "page flip" interrupt > instead of the vblank interrupt, That matches what I saw when I was digging in the code. > in which case missing a single interrupt > could cause a timeout. >=20 >=20 > P.S. Completing the atomic commit and sending the completion event must w= ork > even if user space turns off any CRTCs as part of the commit[0]. So your > hypothesis would be a kernel bug, accidentally turning off the CRTC and/or > not handling a CRTC getting turned off correctly. >=20 > [0] If any CRTC for which the commit has state is off both before and aft= er > the commit though, the commit fails with an error before it could result = in > a timeout.