On Tue, Oct 06, 2015 at 04:10:05PM +0100, John Lewis wrote:
If I disable coreboot framebuffer support in SeaBIOS and then use the VGABIOS from the stock ROM in RW_LEGACY, I don't get any display from SeaBIOS on Broadwell.
If I do the same with a Haswell Chromebook, the display works.
In the former case, SeaBIOS appears to find and load the VGABIOS, according to cbmem, just no display.
I think whatever this problem is may also explain why I'm not able to get display using a modified BOOT_STUB with SeaBIOS on Broadwell.
IIUC, the intel vgabios fails to work properly on some gpus if it is run after the hardware has already been initialized. If that's the case you'd need to be careful to only init the display once (either native coreboot vga + SeaVGABIOS cbvga, or no video in coreboot + SeaBIOS run intel vgabios).
Yes, which is why I removed the intel vgabios from the coreboot part of the ROM, to make sure coreboot wasn't able to initialise it to begin with. The backlight comes on, but I don't get any display until the kernel loads.
So, even if coreboot doesn't initialize the display (no native init and no intel vgabios) and SeaBIOS does run the intel vgabios you still don't get a screen? That's unfortunate.
-Kevin