VGA support

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VGA initialization in coreboot

Since coreboot v4 you can configure VGA initialization in Kconfig. For older versions of coreboot check the history of this page.

First do:

 $ make menuconfig

Then go

    Chipset  --->
     [*] Setup bridges on path to VGA adapter 
     [*] Run VGA option ROMs
     Option ROM execution type (Native mode)  --->

Alternatively you can choose the "Secure mode" to run the VGA option rom in a contained environment.

If you have no on-board graphics, you are done configuring coreboot at this point. You may exit configuration, and run make to get your VGA enabled coreboot image.

On-board Video Devices

If you run coreboot on a system with on-board graphics, you have to embed a VGA on the top level, enter the file name of your option rom and the PCI ID of the associated graphics device in the form <vendor_id>,<device_id>:

   VGA BIOS  --->
    [*] Add a VGA BIOS image
    (oprom-0.rom) VGA BIOS path and filename
    (8086,27a2) VGA device PCI IDs

That's it, exit configuration, and run make to get your VGA enabled coreboot image.

How to retrieve a good video bios

RECOMMENDED: Extracting from your vendor bios image

The recommended method is to take your mainboard vendor's BIOS image and extract the VGA BIOS using a tool called awardeco/amideco/phnxdeco. These tools are available in Debian/Ubuntu. If your vendor bios is award, you would use awardeco, if it's AMI amideco, and if it's Phoenix phnxdeco.

This is the most reliable way:

  • You are guaranteed to get an image that fits to your onboard VGA
  • Even if your VGA BIOS uses self-modifying code you get a correct image

With this method, you may need to pad the image to a certain size, e.g. 64k. This is necessary at least for VIA CN700 chipsets where the factory VGA bios is smaller.

Downloading

There are sites that have video bios roms on their website. (I know of this one for nvidia cards: [1])

Extracting from the system

However you should be able to retrieve your own video bios as well with linux.

  • Boot up a machine with a commercial bios (not coreboot) with the video card you wish to work under coreboot.
  • You can see where and how much your card's bios is using by doing a
cat /proc/iomem | grep 'Video ROM'
  • From the command line enter:
    dd if=/dev/mem of=vgabios.bin bs=1k count=64 skip=768
    This assumes you card's bios is cached at 0xc0000, and is 64K long.

dd if=/dev/mem of=video.bios.bin.4 bs=65536 count=1 skip=12

This works for many of the VIA Epia boards.
Alternatively you can automatically generate it using this nice script from Peter Stuge:

$ cat /proc/iomem | grep 'Video ROM' | (read m; m=${m/ :*}; s=${m/-*}; e=${m/*-}; \
$ dd if=/dev/mem of=vgabios.bin bs=1c skip=$[0x$s] count=$[$[0x$e]-$[0x$s]+1])
  • You now have a video bios image