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

[Peter Robinson]

 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.

Peter