linux-kernel - Re: MGA G200 issue in 6.12 and up

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Message-ID: <Z/2pzDAplsZz8AVd@animx.eu.org>
Date: Mon, 14 Apr 2025 20:35:24 -0400
From: Wakko Warner <wakko@...mx.eu.org>
To: linux-kernel@...r.kernel.org, airlied@...hat.com
Subject: Re: MGA G200 issue in 6.12 and up

I found the fix that works for me.  See below.

Wakko Warner wrote:
> I decided to upgrade to 6.14 on a system with a Matrox G200 onboard vga
> (supermicro X9SCL).
> 
> I use this system via the BMC.  When the mgag200 driver loads, the bmc
> screen flashes between no signal and the screen.  The rate seems to be about
> 1 second no signal and 1 second with signal.
> 
> 6.12 and 6.13 both have this problem.
> 
> 6.11 does not have this problem.
> 
> I have a monitor plugged into the vga port and it doesn't have this problem
> on any of the kernels I've tried.  Only the remote connection through the bmc
> has this problem.  I have booted the system with and with out the monitor
> plugged in, it does not appear to make a difference.

I found a thread on arch linux forums
(https://bbs.archlinux.org/viewtopic.php?id=303819) where the op has the
same issue.  He bisected and came up with the bad commit.
That commit is 
d6460bd52c27fde97d6a73e3d9c7a8d747fbaa3e drm/mgag200: Add dedicated variables
for blanking fields

I searched this commit and manually reverted it from my vanilla 6.14 and it
works fine.  No blinking in the BMC remote console and the external VGA
works fine as well.

-- 
 Microsoft has beaten Volkswagen's world record.  Volkswagen only created 22
 million bugs.