linux-kernel - Re: [PATCH 1/2] drm: introduce page_flip

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Message-ID: <aXOJRWALUJLcGWqh@hal-station.localdomain>
Date: Fri, 23 Jan 2026 09:44:21 -0500
From: Hamza Mahfooz <someguy@...ective-light.com>
To: Christian König <christian.koenig@....com>
Cc: dri-devel@...ts.freedesktop.org,
	Alex Deucher <alexander.deucher@....com>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	Harry Wentland <harry.wentland@....com>,
	Leo Li <sunpeng.li@....com>, Rodrigo Siqueira <siqueira@...lia.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	Sunil Khatri <sunil.khatri@....com>, Ce Sun <cesun102@....com>,
	Lijo Lazar <lijo.lazar@....com>,
	Kenneth Feng <kenneth.feng@....com>,
	Ivan Lipski <ivan.lipski@....com>, Alex Hung <alex.hung@....com>,
	Tom Chung <chiahsuan.chung@....com>, Melissa Wen <mwen@...lia.com>,
	Michel Dänzer <mdaenzer@...hat.com>,
	Fangzhi Zuo <Jerry.Zuo@....com>,
	Timur Kristóf <timur.kristof@...il.com>,
	amd-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] drm: introduce page_flip_timeout()

On Fri, Jan 23, 2026 at 02:52:44PM +0100, Christian König wrote:
> I can only see two reasons why you could run into a timeout:
> 
> 1. A dma_fence never signals.
> 	How that should be handled is already well documented and doesn't require any of this.
> 
> 2. A coding error in the vblank or page flip handler leading to waiting forever.
> 	In that case calling back into the driver doesn't help either.
> 
> So as far as I can see the whole approach doesn't make any sense at all.

It appears that resetting display firmware is able to put at least a
subset of these systems back into a consistent (usable) state. Though, I
don't have a reliable way to reproduce the issue that I'm seeing so I
can't say for sure what it boils down to.