MGA G200 issue in 6.12 and up

[David Airlie]

adding some people

On Tue, Apr 15, 2025 at 10:35 AM Wakko Warner <wakko at animx.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.
>
> --
>  Microsoft has beaten Volkswagen's world record.  Volkswagen only created 22
>  million bugs.
>