[U-Boot] [PATCH 12/12] README: Add instructions for chain-loading U-Boot

[Simon Glass]

Hi Peter,

On 29 May 2017 at 07:29, Peter Robinson <pbrobinson at gmail.com> wrote:
>  On Mon, May 22, 2017 at 12:17 PM, Simon Glass <sjg at chromium.org> wrote:
>> Most Chromebooks support chain-loading U-Boot but instructions are
>> somewhat scattered. Add a README to hold this information within the
>> U-Boot tree. Also add the standard developer keys to simplify the
>> instructions, since they are small.
>>
>> For now this only supports nyan-big.
>>
>> Signed-off-by: Simon Glass <sjg at chromium.org>
>> ---
>>
>>  doc/README.chromium                          | 222 +++++++++++++++++++++++++++
>>  doc/chromium/devkeys/kernel.keyblock         | Bin 0 -> 1208 bytes
>>  doc/chromium/devkeys/kernel_data_key.vbprivk | Bin 0 -> 1199 bytes
>>  3 files changed, 222 insertions(+)
>>  create mode 100644 doc/README.chromium
>>  create mode 100644 doc/chromium/devkeys/kernel.keyblock
>>  create mode 100644 doc/chromium/devkeys/kernel_data_key.vbprivk
>>
>> diff --git a/doc/README.chromium b/doc/README.chromium
>> new file mode 100644
>> index 0000000000..1dd111c65d
>> --- /dev/null
>> +++ b/doc/README.chromium
>> @@ -0,0 +1,222 @@
>> +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. Patch U-Boot
>> +
>> +Open include/configs/tegra124-common.h
>> +
>> +Change:
>> +
>> +#define CONFIG_SYS_TEXT_BASE   0x80110000
>> +
>> +to:
>> +
>> +#define CONFIG_SYS_TEXT_BASE   0x81000100
>
> One query on this one, is it possible to define or override that in
> configs/nyan-big_defconfig rather than in the include file. This would
> be useful from a distro PoV where we build numerous u-boot binaries
> from a single source tree.

Yes I think so. I will have a think about it.

Regards,
Simon