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

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Message-ID: <5c544eef-554f-46f8-942f-0062278abf16@suse.de>
Date: Wed, 16 Apr 2025 10:47:27 +0200
From: Thomas Zimmermann <tzimmermann@...e.de>
To: David Airlie <airlied@...hat.com>, Wakko Warner <wakko@...mx.eu.org>,
 dri-devel <dri-devel@...ts.freedesktop.org>
Cc: linux-kernel@...r.kernel.org
Subject: Re: MGA G200 issue in 6.12 and up

Hi,

thanks for reporting.

Am 16.04.25 um 03:46 schrieb David Airlie:
> adding some people
>
> On Tue, Apr 15, 2025 at 10:35 AM Wakko Warner <wakko@...mx.eu.org> wrote:
>> 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.

I sent out a patch for what I think is the problem. See

https://lore.kernel.org/dri-devel/20250416083847.51764-1-tzimmermann@suse.de/

Testing and feedback would be much appreciated.

Best regards
Thomas

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

-- 
--
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)