Booting FIT kernels

[Joel Stanley]

Hello,

I've switched my kernel development workflow to use a FIT image
containing the machine's dtb, initramfs and kenrel. By copying this
over with tftp and booting it, I can test my changes with a real
openbmc rootfs, but the changes go away once someone else reboots.

This example uses witherspoon. Put the files in the root of your
kernel object tree.

1. Download obmc-phosphor-initramfs-witherspoon.cpio.lzma[1]
2. Download http://ozlabs.org/~joel/openbmc.its
3. Build your kernel with `make`
4. Build your fit with `mkimgage -f openbmc.its myimage`

You now have a FIT image called myimage. Copy it across to your tftp
server and on a u-boot prompt as follows:

ast > setenv serverip <tftp server>
ast > tftp 0x83000000 myimage
ast > bootm 0x83000000

And off it goes! The magic was mostly working out where to find the
.its file. In the future we could include this in the kernel tree and
have a makefile rule that does the FIT-ing for us.

Cheers,

Joel

[1] https://openpower.xyz/job/openbmc-build/distro=ubuntu,target=witherspoon/lastSuccessfulBuild/artifact/images/witherspoon/