u-boot/doc/README.chromium

1 Running U-Boot from coreboot on Chromebooks
4 U-Boot can be used as a secondary boot loader in a few situations such as from
6 ARM platforms to start up the machine.
8 This document aims to provide a guide to booting U-Boot on a Chromebook. It
10 placing this information in the U-Boot tree should make it easier to find for
11 those who use U-Boot habitually.
13 Most of these platforms are supported by U-Boot natively, but it is risky to
17 For all of these the standard U-Boot build instructions apply. For example on
20    sudo apt install gcc-arm-linux-gnueabi
22    make O=b/nyan_big CROSS_COMPILE=arm-linux-gnueabi- nyan-big_defconfig all
26    https://drive.google.com/open?id=0B7WYZbZ9zd-3dHlVVXo4VXE2T0U
30 -----------------------------
34 https://www.chromium.org/chromium-os/firmware-porting-guide/using-nv-u-boot-on-the-samsung-arm-chro…
37 Nyan-big
38 --------
41 https://lists.denx.de/pipermail/u-boot/2015-March/209530.html
42 https://git.collabora.com/cgit/user/tomeu/u-boot.git/commit/?h=nyan-big
43 https://lists.denx.de/pipermail/u-boot/2017-May/289491.html
44 https://github.com/chromeos-nvidia-androidtv/gnu-linux-on-acer-chromebook-13#copy-data-to-the-sd-ca…
46 1. Build U-Boot
49    make -j8 O=b/nyan-big CROSS_COMPILE=arm-linux-gnueabi- nyan-big_defconfig all
58 used by U-Boot. This is because the Chromebook expects to pass it to the
64    ./b/nyan-big/tools/mkimage -f doc/chromium/nyan-big.its u-boot-chromium.fit
66    vbutil_kernel --arch arm --keyblock doc/chromium/devkeys/kernel.keyblock \
67 	--signprivate doc/chromium/devkeys/kernel_data_key.vbprivk \
68 	--version 1 --config dummy.txt --vmlinuz u-boot-chromium.fit \
69 	--bootloader dummy.txt --pack u-boot.kpart
76    sudo cgpt add -b 34 -s 32768 -P 1 -S 1 -t kernel $DISK
77    sudo cgpt add -b 32802 -s 2000000 -t rootfs $DISK
81 5. Write U-Boot to the SD card
83    sudo dd if=u-boot.kpart of=/dev/sdc1; sync
86 6. Start it up
89 do this, login as root (via Ctrl-Alt-forward_arrow) and type
92 Reboot the device with the SD card inserted. Press Clrl-U at the developer
95    U-Boot 2017.07-00637-g242eb42-dirty (May 22 2017 - 06:14:21 -0600)
97    Model: Acer Chromebook 13 CB5-311
98    Board: Google/NVIDIA Nyan-big, ID: 1
102    Tegra124 (Nyan-big) #
111 This is likely due to some problem with change-over of the serial driver
117 To check that you copied the u-boot.its file correctly, use these commands.
118 You should see that the data at 0x100 in u-boot-chromium.fit is the first few
119 bytes of U-Boot:
121    hd u-boot-chromium.fit |head -20
125    hd b/nyan-big/u-boot.bin |head
129 The 'data' property of the FIT is set up to start at offset 0x100 bytes into
131 from the load address. If this changes, you either need to modify U-Boot to be
136 ----------------
140 1. Patch U-Boot
154 2. Build U-Boot
157    make -j8 O=b/chromebook_jerry CROSS_COMPILE=arm-linux-gnueabi- \
165    ./b/chromebook_jerry/tools/mkimage -f doc/chromium/chromebook_jerry.its \
166 	u-boot-chromium.fit
168    vbutil_kernel --arch arm --keyblock doc/chromium/devkeys/kernel.keyblock \
169 	--signprivate doc/chromium/devkeys/kernel_data_key.vbprivk \
170 	--version 1 --config dummy.txt --vmlinuz u-boot-chromium.fit \
171 	--bootloader dummy.txt --pack u-boot.kpart
178 7. Start it up
181 do this, login as root (via Ctrl-Alt-forward_arrow) and type
184 Reboot the device with the SD card inserted. Press Clrl-U at the developer
187    U-Boot 2017.05-00649-g72acdbf-dirty (May 29 2017 - 14:57:05 -0600)
209 --------
213    See: https://www.chromium.org/chromium-os/packages/cros-flashrom
217 --------
219 Coreboot itself is not designed to actually boot an OS. Instead, a program
220 called Depthcharge is used. This originally came out of U-Boot and was then
222 include a very small part of the U-Boot command-line interface but is not
223 usable as a general-purpose boot loader.
226 itself, but instead relies on coreboot. This is similar to (in U-Boot) having
227 a SPI driver with an empty probe() method, relying on whatever was set up
229 what settings are actually used. When chain-loading into U-Boot we must be
230 careful to reinit anything that U-Boot expects. If not, some peripherals (or
234 Finally, it supports only a subset of the U-Boot's FIT format. In particular
236 addresses. This means that U-Boot must be able to boot from whatever
239 (see above) must start at the same address as U-Boot's CONFIG_SYS_TEXT_BASE.