Motherboard Porting Guide
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Documentation is now handled by the same processes we use for code: Add something to the Documentation/ directory in the coreboot repo, and it will be rendered to https://doc.coreboot.org/. Contributions welcome!
Motherboard Porting Guide
Please note that this is WIP work.
HOWTO to find a way
- find the model and manufacturer of your motherboard.
- fetch Coreboot source code: git clone http://review.coreboot.org/p/coreboot
- fetch and built these tools (you'll need to have at least libpci and pciutils installed for some of these):
superiotool: cd coreboot/util/superiotool; make; sudo make install inteltool:cd coreboot/util/inteltool; make; sudo make install ectool: cd coreboot/util/ectool; make; sudo make install dmidecode: git clone https://git.savannah.nongnu.org/git/dmidecode.git msrtool: cd coreboot/util/msrtool; ./configure; make; sudo make install nvramtool: cd coreboot/util/nvramtool; make; sudo make install flashrom: git clone https://review.coreboot.org/flashrom.git
- check that your distro have these tools and install them:
# lspci # dmesg # acpitool # lsusb # acpidump
- Loading this kernel module will be needed for one of the steps below:
# modprobe msr
- Perform these commands as root:
lspci -nnvvvxxxx > lspci.log 2> lspci.err.log lsusb -vvv > lsusb.log 2> lsusb.err.log superiotool -deV > superiotool.log 2> superiotool.err.log inteltool -a > inteltool.log 2> inteltool.err.log ectool -i > ectool.log 2> ectool.err.log msrtool > msrtool.log 2> msrtool.err.log dmidecode > dmidecode.log 2> dmidecode.err.log biosdecode > biosdecode.log 2> biosdecode.err.log nvramtool -x > nvramtool.log 2> nvramtool.err.log dmesg > dmesg.log 2> dmesg.err.log acpidump > acpidump.log 2> acpidump.err.log for x in /sys/class/sound/card0/hw*; do cat "$x/init_pin_configs" > pin_"$(basename "$x")"; done for x in /proc/asound/card0/codec#*; do cat "$x" > "$(basename "$x")"; done cat /proc/cpuinfo > cpuinfo.log 2> cpuinfo.err.log cat /proc/ioports > ioports.log 2> ioports.err.log cat /sys/class/input/input*/id/bustype > input_bustypes.log
- And also these, which may not work on some vendor firmware:
flashrom -V -p internal:laptop=force_I_want_a_brick > flashrom_info.log 2> flashrom_info.err.log flashrom -V -p internal:laptop=force_I_want_a_brick -r rom.bin > flashrom_read.log 2> flashrom_read.err.log
Here's the warning you get when running the above commands without the laptop=force_I_want_a_brick parameter on an unsupported laptop:
======================================================================== WARNING! You seem to be running flashrom on an unsupported laptop. Laptops, notebooks and netbooks are difficult to support and we recommend to use the vendor flashing utility. The embedded controller (EC) in these machines often interacts badly with flashing. See the manpage and https://flashrom.org/Laptops for details. If flash is shared with the EC, erase is guaranteed to brick your laptop and write may brick your laptop. Read and probe may irritate your EC and cause fan failure, backlight failure and sudden poweroff. You have been warned. ========================================================================
- Save all logs in a safe place, as well as the rom.bin file.
- Find what chip does your motherboard use. The name of the chip is present in flashrom_info.log but is not always exact as some chips have several packaging variants (e.g. SOIC-16, SOIC-8 and TSOP). Consult this page for more info on possible chip formats. If possible make a high-resolution (600dpi or higher) scan of the motherboard. Make a scan, not a photo, as cameras typically lack enough resolution to properly identify individual chips.
- try to find information about which EC (if on laptop) or Super I/O chip (if any) is used in your mther board (You may also find some info in Service Manuals or Disassembly Guides)
- try to find the datasheets for your Super I/O / EC chip
For laptop, additionally:
- if you see that ectool returns some fake stuff, like only 'FF' or '00', then you have a custom EC configuration and it'll be a harder work for supporting it.
- if you see that ectool return looks like 'right' output - you have a big chance for support
- you need to figure out the name of the Super I/O / EC chip based on the above log outputs. If you can't find it on the logs, then you'll have to disassemble your laptop to look at the actual chips.
Preparing recovery method
Inevitably when you develop coreboot there will be unbootable builds and so you'll need a way to unbrick your machine after installing a failed image. There are several ways to do so. Main ones are:
In any case you have to locate the flash chip. Note the chipname from flashrom output. Teardown your system and find that chip. For how it usually looks like, consult this page. If you have a scanner, take a high-resolution scan of your motherboard since it may be useful later.
Selecting a Similar Board
The most important criteria for finding a similar board is the chipset. Look at northbridge (device 0:0.0) and southbridge (LPC controller) in the lspci output. Use grep on the coreboot tree to find how those chipsets are named, and then grep for the chipset name (case-insensitive) to find a board which uses it. If there are several of them, try to match (in order of decreasing importance) the system type (desktop/laptop), Super I/O and manufacturer.
Adding a new board
This is a two step process. If your mainboard already exists in the coreboot source tree, skip to next section.
Adding a new vendor to the tree
Create a directory in src/mainboard with the same name as the vendor name. Add to src/mainboard/Kconfig a new vendor entry. The rest of this example uses "foo" vendor.
config VENDOR_FOO bool "Foo"
Add also an include for the new Kconfig file which holds the vendor motherboards in the vendor directory:
Create a src/mainboard/foo/Kconfig file, copying it from some other vendor, and then change the vendor name. Delete all mainboards.
Adding a new motherboard to the tree
Assume in these examples that the vendor name is foo and the board type is bar. Add a new configuration item in src/mainboard/foo/Kconfig:
config BOARD_FOO_BAR bool "BAR"
Add include a board specific config:
Adjusting the contents of the new board directory
Now copy the files of your similar board and start adjusting them. Your first stop is the Kconfig file.
- You need to change the conditional statement in the first line to match your board:
-if BOARD_VENDOR_BAR +if BOARD_VENDOR_BAZ
- Change MAINBOARD_DIR and names.
- Change device options to match your config.
- Next stop is mainboard.c where you should adjust the GPIO config based on the inteltool dump performed above.
- Now you can build it, flash the resulting image and see what fails.
- Later adjust hda_verb.h to get sound working properly (use initial pin dumps for reference).
Look through the options and adjust.
Adjust Kconfig to fit the new vendor/model name and don't forget to change MAINBOARD_DIR and MAINBOARD_PART_NUMBER.