Make it a little more ergonomic than navigating to the chromium.org docs
by just documenting the steps needed to install U-Boot on a Trogdor
chromebook. I've been using the Depthcharge 'altfw' flow to do this
which is nice because you get to keep ChromeOS installed for any future
firmware updates.
Signed-off-by: Stephen Boyd <swb...@chromium.org>
---
doc/board/google/chromebook_trogdor.rst | 69 +++++++++++++++++++++++++
doc/board/google/index.rst | 1 +
2 files changed, 70 insertions(+)
create mode 100644 doc/board/google/chromebook_trogdor.rst
diff --git a/doc/board/google/chromebook_trogdor.rst
b/doc/board/google/chromebook_trogdor.rst
new file mode 100644
index 000000000000..dc40b9072bd5
--- /dev/null
+++ b/doc/board/google/chromebook_trogdor.rst
@@ -0,0 +1,69 @@
+.. SPDX-License-Identifier: GPL-2.0+
+.. sectionauthor:: Stephen Boyd <swb...@chromium.org>
+
+Chromebook Trogdor/Strongbad
+============================
+
+Trogdor and Strongbad are Chromebooks that are either clamshells or
+detachables. U-Boot can be installed into the alternate firmware (altfw) slot
+in the SPI-NOR flash chip and selected in the developer mode boot screen. This
+chain loads U-Boot from Depthcharge and avoids disabling the write protect
+screw.
+
+Enable Alternate Firmware
+=========================
+
+First, you need to enable developer mode on the Chromebook. On a clamshell
+that's done by pressing power + ESC + refresh. On a detachable you press the
+power button + volume up + volume down. Once you get to the recovery screen,
+press Ctrl+d to enter developer mode.
+
+In developer mode, switch to VT2 (use Ctrl+Alt+refresh) and log in as 'root'
+(the default has no password). Configure Depthcharge to load U-Boot::
+
+ cd /tmp
+ flashrom -r bios.bin
+ cat > ubootfw.txt <<EOF
+ 0;uboot;uboot;u-boot for coreboot on ARM
+ 1;uboot;uboot;u-boot for coreboot on ARM
+ EOF
+ cbfstool /tmp/bios.bin remove -r RW_LEGACY -n altfw/list
+ cbfstool bios.bin add -r RW_LEGACY -n altfw/list -f ubootfw.txt -t raw
+
+You can also prevent future ChromeOS firmware updates from replacing the
+alternate firmware::
+
+ cbfstool bios.bin remove -r RW_LEGACY -n cros_allow_auto_update
+
+And finally enable the alternate firmware feature::
+
+ crossystem dev_boot_altfw=1
+
+It's a good idea to flash the RW_LEGACY section now with this alternate
+firwmare list even though we haven't installed U-Boot yet::
+
+ flashrom -w bios.bin -i RW_LEGACY
+
+Installation
+------------
+
+Build U-Boot and obtain u-boot.elf::
+
+ $ make chromebook_trogdor_defconfig
+ $ make
+
+Copy the 'u-boot.elf' file to the Chromebook. On the Chromebook, add the u-boot
+payload::
+
+ cd /tmp
+ flashrom -r bios.bin
+ cbfstool bios.bin add-payload -r RW_LEGACY -c lzma -n uboot -f u-boot.elf
+ flashrom -w bios.bin -i RW_LEGACY
+
+Now you can reboot and select the "Select alternate bootloader" option. Select
+'uboot' to boot U-Boot. If you would like this to be the default boot option,
+you can boot into ChromeOS and switch to VT2 (use Ctrl+Alt+refresh) to use
+crossystem::
+
+ crossystem dev_default_boot=altfw
+
diff --git a/doc/board/google/index.rst b/doc/board/google/index.rst
index 061c79771875..1144b164162c 100644
--- a/doc/board/google/index.rst
+++ b/doc/board/google/index.rst
@@ -9,3 +9,4 @@ Google
chromebook_coral
chromebook_link
chromebook_samus
+ chromebook_trogdor
--
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