VGA support

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:

<source lang="bash">

$ make menuconfig

</source>

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 bios_extract.

$ git clone http://review.coreboot.org/p/bios_extract.git

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

Decompress your rom image with:

$ ./bios_extract hdmag217.rom

If bios_decode fails with a message like

Using file "hdmag217.rom" (513kB)
Found Phoenix BIOS "Phoenix ServerBIOS 3 Release 6.0     "
Version "DEVEL4E0", created on 03/20/06 at 14:37:39.
Error: Invalid module signature at 0x80581

then you have to cut the flash chip description off the image. In this case the BIOS image is 512KB, so you do

$ dd if=hdmag217.rom of=hdma.rom bs=512k count=1
1+0 records in
1+0 records out
524288 bytes transferred in 0.000883 secs (593688784 bytes/sec)

You will get an output similar to this:

Using file "hdma.rom" (512kB)
Found Phoenix BIOS "Phoenix ServerBIOS 3 Release 6.0     "
Version "DEVEL4E0", created on 03/20/06 at 14:37:39.
0x715FC ( 27134 bytes)   ->   romexec_0.rom
0x6E1CB ( 13338 bytes)   ->   strings_0.rom	(29401 bytes)
0x6D65D (  2899 bytes)   ->   display_0.rom	(4128 bytes)
0x6B62E (  8208 bytes)   ->   update_0.rom
0x6B1E3 (  1072 bytes)   ->   decompcode_0.rom			 [0x5000:0xB6D0]
0x6564F ( 23421 bytes)   ->   oprom_0.rom	(36864 bytes)
0x65608 (    44 bytes)   ->   tcpa_H_0.rom	(32 bytes)
0x65592 (    91 bytes)   ->   acpi_1.rom	(116 bytes)
0x65519 (    94 bytes)   ->   acpi_2.rom	(244 bytes)
0x654ED (    13 bytes)   ->   tcpa_*_0.rom
0x64D4F (  1927 bytes)   ->   bioscode_0.rom	(31382 bytes)	 [0xF000:0x856A]
0x60020 ( 19728 bytes)   ->   romexec_1.rom
0x570D9 ( 36656 bytes)   ->   oprom_1.rom	(61440 bytes)
0x4DB9D ( 38177 bytes)   ->   oprom_2.rom	(63488 bytes)
0x46493 ( 30447 bytes)   ->   oprom_3.rom	(65536 bytes)
0x41DAB ( 18125 bytes)   ->   logo_0.rom	(310162 bytes)
0x39CA5 ( 25439 bytes)   ->   oprom_4.rom	(51200 bytes)
0x36005 ( 15493 bytes)   ->   setup_0.rom	(37682 bytes)
0x325D7 ( 14867 bytes)   ->   template_0.rom	(37728 bytes)
0x2FA36 ( 11142 bytes)   ->   miser_0.rom	(16208 bytes)
0x2E63C (  5087 bytes)   ->   tcpa_Q_0.rom	(16096 bytes)
0x2D7C3 (  3678 bytes)   ->   acpi_0.rom	(10464 bytes)
0x1FA2A ( 41023 bytes)   ->   bioscode_1.rom	(56080 bytes)	 [0xE000:0x40F0]
0x14FE0 ( 43567 bytes)   ->   bioscode_2.rom	(62416 bytes)	 [0x6000:0xCC30]
0x0EB4C ( 25721 bytes)   ->   bioscode_3.rom	(36976 bytes)	 [0x6000:0x3BC0]
0x0D0A0 (  6801 bytes)   ->   bioscode_4.rom	(31856 bytes)	 [0x5000:0xBF50]

Now you can check the option roms (oprom_?.rom) with the tool romheaders which is part of the FCode Suite:

$ romheaders oprom_0.rom 

Image 1:
PCI Expansion ROM Header:
  Signature: 0x55aa (Ok)
  CPU unique data: 0x48 0xeb 0x7b 0x01 0x76 0x00 0x00 0x00
                   0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
  Pointer to PCI Data Structure: 0x017c

PCI Data Structure:
  Signature: 0x50434952 'PCIR' (Ok)
  Vendor ID: 0x1002
  Device ID: 0x4752
  Vital Product Data:  0x0000
  PCI Data Structure Length: 0x0018 (24 bytes)
  PCI Data Structure Revision: 0x00
  Class Code: 0x030000 (VGA Display controller)
  Image Length: 0x0048 blocks (36864 bytes)
  Revision Level of Code/Data: 0x0421
  Code Type: 0x00 (Intel x86)
  Last-Image Flag: 0x80 (last image in rom)
  Reserved: 0x0000

Platform specific data for x86 compliant option rom:
  Initialization Size: 0x48 (36864 bytes)
  Entry point for INIT function: 0x80

Congratulations, that's your option rom (compare PCI IDs and Class Code to find it among the option roms).

Downloading

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

For Intel onboard graphics you can download the vbios(vga bios) from Intel's download section. The vbios is included with some versions of the graphics driver. The summary will say something like "NOTE:These materials are intended for use by developers.Includes VBIOS". The actual vbios file is the *.dat file included with the graphics driver.

Extracting from the system (if everything else fails)

However you might be able to retrieve your on-board video bios with Linux as well.

• 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

<source lang="bash">cat /proc/iomem | grep 'Video ROM'</source>

• From the command line enter:
  <source lang="bash">dd if=/dev/mem of=vgabios.bin bs=1k count=64 skip=768</source> This assumes you card's bios is cached at 0xc0000, and is 64K long.

<source lang="bash">dd if=/dev/mem of=video.bios.bin.4 bs=65536 count=1 skip=12</source> This works for many of the VIA Epia boards.
Alternatively you can automatically generate it using this nice script from Peter Stuge:
<source lang="bash"> 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]) </source>

• You now have a video bios image