[coreboot] Geode LX VGA BIOS Patch

Chris Kindt chriskindt at umbc.edu
Tue Aug 25 20:54:48 CEST 2009

Another Updated Patch:

    So far I have heard of problems when using a lcd connected to the 
vga port and when switching from X to back to the console. I was able to 
replicate problems and address them with this patch.

    For the lcd issues, the left side of the screen was distorted and 
cropped.  This was a timing problem from using incorrect modes. My crt 
was able to function correctly with these modes.  There were two issues 
with the mode table. When creating the patch I copied the original 
seabios table instead of the geodelx modified table. Then even with the 
correct geodelx table, the seabios table is still addressed at compile 
time. The geodelx-v3 patch includes the modified table, while the 
geodelx-modehack patch is a temporary quick fix to address the right table.

    For switching from X to the console, the display controller 
registers need to be reset to enable vga . These are DC_GENERAL_CFG=0x80 
and DC_DISPLAY_CFG=0x48. The linux vgacon vt driver only saves the 
standard vga io ports and memory. I am looking into doing this with vesa 
extensions from X.  For now an easy way to do this is to re-post the 
vgabios with vbetool or svgalib. I removed exiting if legacy io checking 
fails so reposting is possible.

    -replaced video parameter table
    -removed quiting when legacy io fails
    -fixed spelling

    -temporary fix to use correct video timing 

        Chris Kindt

Signed-off-by: Chris Kindt <chriskindt at umbc.edu>
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