Re: [Linux-fbdev-devel] Matrox G550, dual head, 1680x1050

["Hans-Jürgen Koch" <hjk@linutronix.de>]

Am Dienstag, 6. März 2007 10:25 schrieb Petr Vandrovec:
> Hans-Jürgen Koch wrote:
> > Am Montag, 5. März 2007 05:59 schrieb Petr Vandrovec:
> >> Can you try setting vxres for second head from 1680 to 1696, or 1728?
> >> Maybe X look at vxres and not at framebuffer line length (what fbset -i
> >> reports for line length?)
> >
> > Here are more details:
> >
> > 1.) I boot my kernel (vanilla 2.6.20.1) with the following parameters:
> >
> > video=matroxfb:outputs:120,pixclock:7380,xres:1680,yres:1050,upper:32,
> >                lower:4,left:32,right:224,hslen:136,vslen:4,depth:32
> >
> > This initializes the primary head correctly. The second head is probably
> > wrong, because the monitor's on screen message complains about a
> > non-ideal resolution.
>
> Second head always starts in 640x480/32bpp.  You have to use fbset to
> switch it to different mode, so matroxfb works fine as far as I can tell.
>
> > As you can see, the second monitor fell back to VGA resolution, but the
> > logs tell that X thinks it successfully switched to 1680x1050. The KDE
> > control center reports the same. The image on the second monitor is
> > distorted.
>
> Because X (mga driver) was programming hardware...
>
> > 4.) I then issue the following command:
> >
> > $ fbset -fb /dev/fb1 -g 1680 1050 1696 1050 32 -t 7380 224 32 32 4 136 4
> >
> > With that, the image on the second monitor immediately becomes clear, and
> > I have a fully working xinerama configuration then.
>
> Yes, and this corrects X programming mistake.
>
> > As far as I can see, fbset is the only way to initialize the second head
> > properly. Neither matroxfb nor mga do it correctly with 1680x1050.
>
> Well, fbset == matroxfb, so I do not quite understand your complaint.
> 							

If matroxfb deliberately initializes the second head to 640x480/32bpp, then it 
is OK. I thought the kernel boot parameters would apply to both heads. But on 
second thought, I agree, it has to be that way. Otherwise you'd run into 
trouble if you had two different monitors connected as there are no 
individual settings for both heads.

Thanks for your explanations!

Hans