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choalla

Member

Registered: 2018-09-06

Posts: 2

xf86-video-mga xorg driver not playing nice with mgag200 module

I have a fresh Arch installation on a Dell Poweredge R730. I installed the xf86-video-mga driver via the AUR. I ended up removing the "X-ABI-VIDEODRV_VERSION<23, X-ABI-VIDEODRV_VERSION>=24" conflicts from the PKGBUILD because that was the only way I could tell of getting the thing to install properly given xorg-server installed is 1.20. I figured this could potentially cause runtime problems in xorg, but I don't think it's precipitating the problem I'm currently having.

Before installing the mga driver, I had been able to "successfully" start X windows, I assume using the modesetting driver (no xorg confs at all). The problem is that the performance was abysmal. Even doing basic things like dragging windows around is abhorrently laggy.

Per the mga instructions, I configured X to use the "mga" driver. /etc/X11/xorg.conf.d/20-mga.conf:

Section "Device"
    Identifier "Card0"
    Driver "mga"
EndSection

However, when starting X windows, I get the error (in the log file):

(EE) mga: The PCI device 0xABC at XY@00:00.0 has a kernel module claiming it.
(EE) mga: This driver cannot operate until it has been unloaded

Okay, so what module is being used by the card?

$ lspci -l | grep -A4 VGA
XY@00.0 VGA compatible controller: Matrox Electronics Systems Ltd.  G200eR2 (rev01)
        DeviceName: EmbeddedVideo
        Subsystem: Dell G200eR2
        Kernel driver in use: mgag200
        Kernel modules: mgag200

Okay, can I unload that module?

$ modprobe -r mgag200
modprobe: FATAL: Module mgag200 is in use.

So I can't unload it, which I glean would be necessary for the mga driver to load. Out of curiosity, I tried blacklisting the mgag200 module, but that just causes the display to stop updating shortly after boot.

I am unsure what to try next. Any help or direction at all would be appreciated.

Last edited by choalla (2018-09-06 20:03:17)

Gusar

Member

Registered: 2009-08-25

Posts: 3,607

Re: xf86-video-mga xorg driver not playing nice with mgag200 module

What kind of a machine is this? Is it a server board with an integrated g200 gpu, or an old system with an actual Matrox card in it? The mgag200 module was created for server boards, not for the old cards.

Anyway, here's some things to try:
1) Boot with nomodeset on the kernel commandline. That will stop the mgag200 module from loading and you can try your luck with the xf86-video-mga driver. I kinda doubt the driver still works though, you might need to downgrade xorg-server to get it running.

2) Don't bother with xf86-video-mga, use the default modesetting driver, but disable glamor acceleration. I believe this is what causes your abysmal performance - modesetting is using glamor, but without a 3D driver for Matrox gpus you're getting a software fallback. To disable glamor, create /etc/X11/xorg.conf.d/20-modesetting.conf that contains the following:

Section "Device"
  Identifier "Matrox"
  Driver "modesetting"
  Option "AccelMethod" "none"
EndSection

Last edited by Gusar (2018-09-06 20:49:01)

choalla

Member

Registered: 2018-09-06

Posts: 2

Re: xf86-video-mga xorg driver not playing nice with mgag200 module

It's a Dell Poweredge R730 server, so it's got the integrated graphics.

I tried your second suggestion since it was easiest. Seems to have done the trick! Thanks for your help. I may try the first one just to see what happens.