mirror of
https://github.com/AsahiLinux/u-boot
synced 2024-11-27 07:01:24 +00:00
9d73e85a87
The current documentation only covers how to chain-load U-Boot on a Chromebook. Add more information about the other ways to use U-Boot on Chromebooks. In particular it is again possible to build it with Chromium OS verified boot. Signed-off-by: Simon Glass <sjg@chromium.org>
239 lines
7.2 KiB
Text
239 lines
7.2 KiB
Text
Running U-Boot from coreboot on Chromebooks
|
|
===========================================
|
|
|
|
U-Boot can be used as a secondary boot loader in a few situations such as from
|
|
UEFI and coreboot (see README.x86). Recent Chromebooks use coreboot even on
|
|
ARM platforms to start up the machine.
|
|
|
|
This document aims to provide a guide to booting U-Boot on a Chromebook. It
|
|
is only a starting point, and there are many guides on the interwebs. But
|
|
placing this information in the U-Boot tree should make it easier to find for
|
|
those who use U-Boot habitually.
|
|
|
|
Most of these platforms are supported by U-Boot natively, but it is risky to
|
|
replace the ROM unless you have a servo board and cable to restore it with.
|
|
|
|
|
|
For all of these the standard U-Boot build instructions apply. For example on
|
|
ARM:
|
|
|
|
sudo apt install gcc-arm-linux-gnueabi
|
|
mkdir b
|
|
make O=b/nyan_big CROSS_COMPILE=arm-linux-gnueabi- nyan-big_defconfig all
|
|
|
|
You can obtain the vbutil_kernel utility here:
|
|
|
|
https://drive.google.com/open?id=0B7WYZbZ9zd-3dHlVVXo4VXE2T0U
|
|
|
|
|
|
Snow (Samsung ARM Chromebook)
|
|
-----------------------------
|
|
|
|
See here:
|
|
|
|
https://www.chromium.org/chromium-os/firmware-porting-guide/using-nv-u-boot-on-the-samsung-arm-chromebook
|
|
|
|
|
|
Nyan-big
|
|
--------
|
|
|
|
Compiled based on information here:
|
|
https://lists.denx.de/pipermail/u-boot/2015-March/209530.html
|
|
https://git.collabora.com/cgit/user/tomeu/u-boot.git/commit/?h=nyan-big
|
|
https://lists.denx.de/pipermail/u-boot/2017-May/289491.html
|
|
https://github.com/chromeos-nvidia-androidtv/gnu-linux-on-acer-chromebook-13#copy-data-to-the-sd-card
|
|
|
|
1. Build U-Boot
|
|
|
|
mkdir b
|
|
make -j8 O=b/nyan-big CROSS_COMPILE=arm-linux-gnueabi- nyan-big_defconfig all
|
|
|
|
|
|
2. Select a .its file
|
|
|
|
Select something from doc/chromium which matches your board, or create your
|
|
own.
|
|
|
|
Note that the device tree node is required, even though it is not actually
|
|
used by U-Boot. This is because the Chromebook expects to pass it to the
|
|
kernel, and crashes if it is not present.
|
|
|
|
|
|
3. Build and sign an image
|
|
|
|
./b/nyan-big/tools/mkimage -f doc/chromium/nyan-big.its u-boot-chromium.fit
|
|
echo test >dummy.txt
|
|
vbutil_kernel --arch arm --keyblock doc/chromium/devkeys/kernel.keyblock \
|
|
--signprivate doc/chromium/devkeys/kernel_data_key.vbprivk \
|
|
--version 1 --config dummy.txt --vmlinuz u-boot-chromium.fit \
|
|
--bootloader dummy.txt --pack u-boot.kpart
|
|
|
|
|
|
4. Prepare an SD card
|
|
|
|
DISK=/dev/sdc # Replace with your actual SD card device
|
|
sudo cgpt create $DISK
|
|
sudo cgpt add -b 34 -s 32768 -P 1 -S 1 -t kernel $DISK
|
|
sudo cgpt add -b 32802 -s 2000000 -t rootfs $DISK
|
|
sudo gdisk $DISK # Enter command 'w' to write a protective MBR to the disk
|
|
|
|
|
|
5. Write U-Boot to the SD card
|
|
|
|
sudo dd if=u-boot.kpart of=/dev/sdc1; sync
|
|
|
|
|
|
6. Start it up
|
|
|
|
Reboot the device in dev mode. Make sure that you have USB booting enabled. To
|
|
do this, login as root (via Ctrl-Alt-forward_arrow) and type
|
|
'enable_dev_usb_boot'. You only need to do this once.
|
|
|
|
Reboot the device with the SD card inserted. Press Clrl-U at the developer
|
|
mode screen. It should show something like the following on the display:
|
|
|
|
U-Boot 2017.07-00637-g242eb42-dirty (May 22 2017 - 06:14:21 -0600)
|
|
|
|
Model: Acer Chromebook 13 CB5-311
|
|
Board: Google/NVIDIA Nyan-big, ID: 1
|
|
|
|
Net: No ethernet found.
|
|
Hit any key to stop autoboot: 0
|
|
Tegra124 (Nyan-big) #
|
|
|
|
|
|
7. Known problems
|
|
|
|
On the serial console the word MMC is chopped at the start of the line:
|
|
|
|
C: sdhci@700b0000: 2, sdhci@700b0400: 1, sdhci@700b0600: 0
|
|
|
|
This is likely due to some problem with change-over of the serial driver
|
|
during relocation (or perhaps updating the clock setup in board_init()).
|
|
|
|
|
|
9. Notes
|
|
|
|
To check that you copied the u-boot.its file correctly, use these commands.
|
|
You should see that the data at 0x100 in u-boot-chromium.fit is the first few
|
|
bytes of U-Boot:
|
|
|
|
hd u-boot-chromium.fit |head -20
|
|
...
|
|
00000100 b8 00 00 ea 14 f0 9f e5 14 f0 9f e5 14 f0 9f e5 |................|
|
|
|
|
hd b/nyan-big/u-boot.bin |head
|
|
00000000 b8 00 00 ea 14 f0 9f e5 14 f0 9f e5 14 f0 9f e5 |................|
|
|
|
|
|
|
The 'data' property of the FIT is set up to start at offset 0x100 bytes into
|
|
the file. The change to CONFIG_SYS_TEXT_BASE is also an offset of 0x100 bytes
|
|
from the load address. If this changes, you either need to modify U-Boot to be
|
|
fully relocatable, or expect it to hang.
|
|
|
|
|
|
chromebook_jerry
|
|
----------------
|
|
|
|
The instruction are similar to those for Nyan with changes as noted below:
|
|
|
|
1. Patch U-Boot
|
|
|
|
Open include/configs/rk3288_common.h
|
|
|
|
Change:
|
|
|
|
#define CONFIG_SYS_TEXT_BASE 0x00100000
|
|
|
|
to:
|
|
|
|
#define CONFIG_SYS_TEXT_BASE 0x02000100
|
|
|
|
|
|
|
|
2. Build U-Boot
|
|
|
|
mkdir b
|
|
make -j8 O=b/chromebook_jerry CROSS_COMPILE=arm-linux-gnueabi- \
|
|
chromebook_jerry_defconfig all
|
|
|
|
|
|
3. See above
|
|
|
|
4. Build and sign an image
|
|
|
|
./b/chromebook_jerry/tools/mkimage -f doc/chromium/chromebook_jerry.its \
|
|
u-boot-chromium.fit
|
|
echo test >dummy.txt
|
|
vbutil_kernel --arch arm --keyblock doc/chromium/devkeys/kernel.keyblock \
|
|
--signprivate doc/chromium/devkeys/kernel_data_key.vbprivk \
|
|
--version 1 --config dummy.txt --vmlinuz u-boot-chromium.fit \
|
|
--bootloader dummy.txt --pack u-boot.kpart
|
|
|
|
|
|
5. See above
|
|
|
|
6. See above
|
|
|
|
7. Start it up
|
|
|
|
Reboot the device in dev mode. Make sure that you have USB booting enabled. To
|
|
do this, login as root (via Ctrl-Alt-forward_arrow) and type
|
|
'enable_dev_usb_boot'. You only need to do this once.
|
|
|
|
Reboot the device with the SD card inserted. Press Clrl-U at the developer
|
|
mode screen. It should show something like the following on the display:
|
|
|
|
U-Boot 2017.05-00649-g72acdbf-dirty (May 29 2017 - 14:57:05 -0600)
|
|
|
|
Model: Google Jerry
|
|
Net: Net Initialization Skipped
|
|
No ethernet found.
|
|
Hit any key to stop autoboot: 0
|
|
|
|
|
|
8. Known problems
|
|
|
|
None as yet.
|
|
|
|
|
|
9. Notes
|
|
|
|
None as yet.
|
|
|
|
|
|
Other notes
|
|
===========
|
|
|
|
flashrom
|
|
--------
|
|
|
|
Used to make a backup of your firmware, or to replace it.
|
|
|
|
See: https://www.chromium.org/chromium-os/packages/cros-flashrom
|
|
|
|
|
|
coreboot
|
|
--------
|
|
|
|
Coreboot itself is not designed to actually boot an OS. Instead, a program
|
|
called Depthcharge is used. This originally came out of U-Boot and was then
|
|
heavily hacked and modified such that is is almost unrecognisable. It does
|
|
include a very small part of the U-Boot command-line interface but is not
|
|
usable as a general-purpose boot loader.
|
|
|
|
In addition, it has a very unusual design in that it does not do device init
|
|
itself, but instead relies on coreboot. This is similar to (in U-Boot) having
|
|
a SPI driver with an empty probe() method, relying on whatever was set up
|
|
beforehand. It can be quite hard to figure out between these two code bases
|
|
what settings are actually used. When chain-loading into U-Boot we must be
|
|
careful to reinit anything that U-Boot expects. If not, some peripherals (or
|
|
the whole machine) may not work. This makes the process of chainloading more
|
|
complicated than it could be on some platforms.
|
|
|
|
Finally, it supports only a subset of the U-Boot's FIT format. In particular
|
|
it uses a fixed address to load the FIT and does not support load/exec
|
|
addresses. This means that U-Boot must be able to boot from whatever
|
|
address Depthcharge happens to use (it is the CONFIG_KERNEL_START setting
|
|
in Depthcharge). In practice this means that the data in the kernel@1 FIT node
|
|
(see above) must start at the same address as U-Boot's CONFIG_SYS_TEXT_BASE.
|