[Solved] Intel graphics framebuffer glitch

[pvc]

I am experimenting with display mode setting for Intel integrated graphics and I am having some trouble. I am able to switch between different display modes (like 640x400@70, 640x480@60, 1024x768@60, etc.) but some pixel columns seem to be glitched, no matter which display mode is being used. Attachments show what the problem is. It's almost like pixel stream doesn't match with frame timings. BTW. Im testing on G31 (GMA 3100) chipset but I only have documentation for G35 (GMA X3500).

[pvc]

I can't believe it took me this long to find it.

Turns out that I did not mask low bits of GMADR register when reading it from PCI config space. Instead 0xE0000000 I used 0xE0000008 address as graphics memory base. Last 8 looked so similar to other 0s on the screen in VGA font. I did see it only after setting up serial connection (and whole CLI) to the machine and using some semi-decent font in terminal emulator.

[kzinti]

Hehe... Yeah it has happened to me in the past. Frustrating.

[eekee]

Remote login of one sort or another is extremely useful when developing window systems.