On Thu, Jan 22, 2009 at 10:12:04PM +0200, Ville Syrjälä wrote:

On Thu, Jan 22, 2009 at 08:22:48PM +0200, Risto Suominen wrote:

quoted

Since the complete re-write in 2.6.10, some PowerMacs (At least PowerMac 5500
and PowerMac G3 Beige rev A) with ATI Mach64 chip have suffered from unstable
columns in their framebuffer image. This seems to depend on a value (4) read
from PLL_EXT_CNTL register, which leads to incorrect DSP config parameters to
be written to the chip. This patch uses a value calculated by aty_init_pll_ct
instead, as a starting point.

AFAICS it should be the right thing to do on other systems too. I have
a good collection of mach64 pci cards and laptops so I'll try to find
some time next week to test that theory on x86.

Well, the experiment failed on the first Mobility I tried. The FIFO
calculations aren't obvious from the code and there's no mention how
to actually calculate them in the programming guide. So I guess special
casing powermacs is the best way forward.

-- 
Ville Syrjälä
syrjala@sci.fi
http://www.sci.fi/~syrjala/