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

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Message-ID: <hyyyuqsyf7c3ed2ku57fp4sjwkpcacygtrwnkgupn2xdq7ez4u@sg6xeg4shkdd>
Date: Thu, 9 Oct 2025 19:56:03 -0400
From: Nick Bowler <nbowler@...conx.ca>
To: Thomas Zimmermann <tzimmermann@...e.de>
Cc: Doug Anderson <dianders@...omium.org>, linux-kernel@...r.kernel.org, 
	dri-devel@...ts.freedesktop.org, regressions@...ts.linux.dev
Subject: Re: PROBLEM: AST2500 BMC video output disabled by reboot (regression)

Hello,

On Tue, Oct 07, 2025 at 10:51:29AM +0200, Thomas Zimmermann wrote:
> Am 04.10.25 um 02:31 schrieb Nick Bowler:
> > But it introduces a new problem: the screen no longer turns back on if
> > I boot the patched kernel from the "display off" state.  The unpatched
> > 6.17 kernel would at least turn the display back on from this.
> > Furthermore, rebooting from this state keeps the display off.
[...]
> Thanks again for testing. Looks like your BMC is especially picky about
> these settings. :)
> 
> Attached are two patches; each trying to eliminate one of the possible
> causes. Could you please test them individually and report the results?

0001-ast-Use-VGACR17-sync-enable-and-VGACRB6-sync-off.patch
  ^ Everything appears to work fine with this patch applied on
    top of 6.17.

0001-ast-Use-VGACR17-sync-enable-and-VGASR01-screen-disab.patch
  ^ This one has the same problem as the last patch: the screen
    does not turn back on if it was previously off during bootup.

Thanks,
  Nick