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[84.1.223.139]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4806cddffc0sm151978565e9.5.2026.01.29.03.25.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Jan 2026 03:25:45 -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 , Fangzhi Zuo , amd-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] drm: introduce page_flip_timeout() Date: Thu, 29 Jan 2026 12:25:44 +0100 Message-ID: <2719069.vYhyI6sBWr@timur-hyperion> In-Reply-To: <6f1239d2-eec3-40b6-aca7-5b278350dd04@mailbox.org> References: <20260123000537.2450496-1-someguy@effective-light.com> <6f1239d2-eec3-40b6-aca7-5b278350dd04@mailbox.org> 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 Thursday, January 29, 2026 11:06:11=E2=80=AFAM Central European Standard= Time=20 Michel D=C3=A4nzer wrote: > >>>=20 > >>> Christian, why would the CRTC be turned off? > >>=20 > >> Exactly that's the question we need to answer. > >>=20 > >> But from what you describe the CRTC keeps on, just doesn't send any mo= re > >> vblank events.>=20 > > The vblank interrupt source getting accidentally disabled might be one > > possible cause though. > Another possibility is that test-only commits with the > DRM_MODE_ATOMIC_TEST_ONLY flag (which can happen in parallel while the > kernel is processing a "real" commit) accidentally have side effects on t= he > current kernel state, resulting in the "real" commit failing to do > something it should. There have been bugs like that in the amdgpu DM code > before. >=20 >=20 > Anyway, this is all speculation. Somebody just needs to dig in and get to > the bottom of why the commits aren't getting completed. Yes, I agree. However, just like we do with ring timeouts, we also need to be prepared fo= r=20 the situation where a page flip timeout happens and we should try to recove= r=20 from it. And if it isn't recoverable, fall back to GPU reset. I strongly suspect that there are many different issues depending on the=20 hardware generation and display configuration. There isn't going to be a si= lver=20 bullet to fix all of them, and in case it cannot be fixed, I think a GPU re= set=20 is the right thing to do - it's drastic, but still better than letting the= =20 machine just freeze irrecoverably. One example of such a bug was fixed by 6cbe6e072c5d where DC was trying to = use=20 an interrupt that didn't exist on some hardware. This type of bug would be= =20 impossible for userspace to solve in any way, but a GPU reset would have=20 helped to recover the machine into a usable state. Another example would be Strix Halo with adaptive sync and/or tearing updat= es=20 enabled, which 100% reproduces a page flip timeout for me. I haven't had ti= me=20 to investigate that one just yet. Timur