linux-kernel - Re: PROBLEM: AST2500 BMC video output disabled by reboot (regression)

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Message-ID: <b0cbc791-a209-4756-acf0-e869888294ac@suse.de>
Date: Wed, 17 Sep 2025 11:22:22 +0200
From: Thomas Zimmermann <tzimmermann@...e.de>
To: Nick Bowler <nbowler@...conx.ca>, linux-kernel@...r.kernel.org,
 dri-devel@...ts.freedesktop.org, regressions@...ts.linux.dev
Cc: Douglas Anderson <dianders@...omium.org>
Subject: Re: PROBLEM: AST2500 BMC video output disabled by reboot (regression)

Hi

Am 21.04.25 um 06:26 schrieb Nick Bowler:
> Hi,
>
> I recently noticed that on current kernels I lose video output from
> my Blackbird's AST2500 BMC after a reboot, which makes it difficult to
> boot the system again (the video output will come on only after Linux
> is booted again).
>
> With Linux 6.6 and earlier, there is no problem rebooting, everything
> is fine.
>
> I bisected to this commit:
>
>    ce3d99c8349584bc0fbe1e21918a3ea1155343aa is the first bad commit
>    commit ce3d99c8349584bc0fbe1e21918a3ea1155343aa
>    Author: Douglas Anderson <dianders@...omium.org>
>    Date:   Fri Sep 1 16:39:53 2023 -0700
>
>        drm: Call drm_atomic_helper_shutdown() at shutdown time for misc drivers
>
> This commit does not revert cleanly on 6.14, but I can easily undo
> the changes this commit made to the ast driver, and this is enough
> to restore working behaviour.
>
> Let me know if you need any more info!

Would you be able to test a patch?

Best regards
Thomas

>
> Thanks,
>    Nick

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)