[Nouveau] Clock speed for GeForce 6100

[Mihai Georgian]

Hi,

The nouveau driver on my MSI K9N6GM (GeForce 6100 nForce 405)
motherboard generates a dot clock speed which is about 8% lower than the
value given in xorg.conf. The same happens with the nv driver. The same
appears to happen with other motherboards with GeForce 6100 (see
Bugzilla – Bug 12002).

I have seen reports of nVidia using the PCIE clock / 4 to drive some of
their cards and I noticed that 27000 / 25000 = 1.08. Applying the
following patch resolved my problem and now the nouveau driver works
fine for me:

diff -ur xf86-video-nv-2.1.6/nouveau-20070920/src/nv_setup.c
xf86-video-nv-2.1.6.mihai/nouveau-20070920/src/nv_setup.c
--- xf86-video-nv-2.1.6/nouveau-20070920/src/nv_setup.c 2007-09-19
23:17:39.000000000 +0100
+++ xf86-video-nv-2.1.6.mihai/nouveau-20070920/src/nv_setup.c
2008-06-01 15:45:53.000000000 +0100
@@ -333,7 +333,10 @@
     if(pNv->twoHeads && (implementation != CHIPSET_NV11))
     {
        if(nvReadEXTDEV(pNv, 0x0000) & (1 << 22))
-           pNv->CrystalFreqKHz = 27000;
+           if(implementation == CHIPSET_C512)
+               pNv->CrystalFreqKHz = 25000;
+           else
+               pNv->CrystalFreqKHz = 27000;
     }

     pNv->CURSOR           = NULL;  /* can't set this here */

A similar patch fixed the nv driver.

The above patch is against the nouveau version which comes with Fedora 8
but, looking at the current git, it appears that this part of the code
hasn't changed recently.

Regards,

Mihai