U-Boot

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U-boot is the bootloader commonly used on our allwinner SoCs. Amongst others, it provides the basic infrastructure to bring up a board to a point where it can load a linux kernel and start booting your operating system.

Contents

Compile U-Boot

Get a toolchain

If you haven't done so before, get a suitable toolchain installed and added to your PATH.

Clone the repository

You can clone our u-boot repository by running:

git clone https://github.com/linux-sunxi/u-boot-sunxi.git

This should checkout the sunxi branch, which allows booting from SD, over USB and over ethernet, but it still lacks support for booting off the NAND. For more information about booting from NAND, check the NAND howto.

Note: the 'sunxi' branch in the u-boot-sunxi repository is currently under active development and also frequently merges in the changes from the upstream u-boot. Expect it to be occasionally broken. There is no stable branch or tag at the moment. If something does not work correctly, please consider trying older revisions from the 'sunxi' branch or look for any possible not-yet-applied fixes in the linux-sunxi and u-boot mailing lists.

Determine build target

You can list the available u-boot targets by running:

grep sunxi boards.cfg | awk '{print $7}'

You will notice that some board names are duplicates, but with _FEL attached. These are for use with USBBoot, while the standard ones will boot from SD.

Build

When you have determined what target you want to build, configure:

make CROSS_COMPILE=arm-linux-gnueabihf- {TARGET}_config 

Then just build it:

make CROSS_COMPILE=arm-linux-gnueabihf- 

You might want to add '-j4' to make use of 4 processors (or any number that matches your system), to speed up the build.

Boot

When the build has completed, there will be spl/sunxi-spl.bin and u-boot.img available in your u-boot tree.

For getting these bits loaded onto the hardware, please refer to the respective howto:

Configure U-Boot

TODO: Move these to their respective howtos

Setting environment variables

There is a difference in setting environment variables between the boot script and the u-boot shell.

Inside the shell you would set, for instance:

setenv root /dev/sda1

But in the script you would use:

root=/dev/sda1

SD Card

setenv bootargs console=ttyS0,115200 root=/dev/mmcblk0p2 rootwait panic=10 ${extra}
ext2load mmc 0 0x43000000 script.bin
ext2load mmc 0 0x48000000 uImage
bootm 0x48000000

NAND

Example u-boot environment, as found in uEnv.txt from a stock android u-boot environment partition

bootdelay=0
bootcmd=run setargs boot_normal
console=ttyS0,115200
nand_root=/dev/nandc
mmc_root=/dev/mmcblk0p4
init=/init
loglevel=8
setargs=setenv bootargs console=${console} root=${nand_root} init=${init} loglevel=${loglevel}
boot_normal=nand read 40007800 boot;boota 40007800
boot_recovery=nand read 40007800 recovery;boota 40007800
boot_fastboot=fastboot

NFS

Recent version of u-boot are able to boot from NFS as well as TFTP, but you have to get rid of the automatic setup of FTP. Check Ethernet for more information.

Note: on the A20 based cubieboards, this only seems to work on the stable kernel, not on stage.

FB console

To get u-boot output shown on the built-in framebuffer driver (currently, HDMI only at 1024x768), add the following to your boot.cmd:

setenv stdout=serial,vga
setenv stderr=serial,vga

The default environment has these values set as well.

Adding a new device to U-Boot

dram config

With the output from bootinfo or a10-meminfo, you can now create a dram file for your device in board/sunxi/ The output from either program trivially applies to a u-boot sunxi dram file.

First, try to match your settings with an existing dram file. There are a lot of generic dram files available for a10, perhaps one of those matches your config. If an existing board config for another device matches yours, then please consider turning this into a generic dram file.

If nothing matches, copy an existing file to a filename relevant for your device and edit the entries manually. Do not forget to git add this new file.

Add dram file to build system

Edit board/sunxi/Makefile to add a line which links your device with the right dram_ object.

Add board to boards.cfg

boards.cfg, in the top level of your u-boot tree, holds all board configurations.

Scroll down until you find the sunxi devices, and create an entry for your device.

Build and run the new u-boot

That's it. You should now be able to compile and test u-boot. It makes sense to also get a kernel and operating system running to more completely test the u-boot dram settings before committing code.

Commit your work to the git tree and send in the patch

You can now commit your changes, and with:

git format-patch -M -C HEAD^

You will create a git mbox patch file which you can mail to our mailinglist. If you have set up git correctly, you can just run:

git send-email 0001-*.patch

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