Kontron MiniITX Board 886LCDn (Intel 855GM) - No display output with i810 driver

Peter Kunzmann kunzmann at citron.de
Thu Jun 22 02:24:33 PDT 2006

We have some problems with the video driver for the i855GM of an Kontron 
Board. The driver works with CRT and LFP as expected but with DFP there 
are some problems. DFP is used over an expansion Card from Kontron with 
an CH7301 Chip connected via DVO. There is no problem for resolutions up 
to 1024x768 if you choose a higer one, the monitor show no signal.

The Driver is the actual driver from the xorg git repository. For 
testing I  have added two patches from airlied
( http://people.freedesktop.org/~airlied/i830_server_diffs and 
http://www.skynet.ie/~airlied/patches/i810/i810_raw_mode.diff )

Some changes were made to match the patches with the current version of 
the git repository. The rawmode which are proviede by the patches is not 
used. But with this patches there are lot of DEBUG messages. With the 
help of this messages the problems seems to be that the settings for the 
PLL are not right with higher resolutions. Another thing is that the 
Settings for the PLL is the same for 1024x768, 1280x1024 and 1600x1200. 
So I think the error can be found in this direction. Without the above 
mentioned patch the driver shows the same behaviour. With the same 
settings in xorg.conf the driver works with the different resolutions 
with LFP and CRT only DFP is not working correctly with resolutions 
higher than 1024x786.

My first thought was that there is a problem with an maximum value, 
which is not high enough. But now I think there is a general problem 
with the settings for the PLL over DFP!!

Peter Kunzmann

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