[U-Boot] Getting the reboot/reset reason through to the kernel

[Chris Packham]

On Wed, Jun 12, 2019 at 11:18 AM Chris Packham <judge.packham at gmail.com> wrote:
>
> Hi List,
>
> Sorry for a vague general post.
>
> I know that a number of SoCs have a reset reason register so that they
> can distinguish between power-on reset vs reset line input vs watchdog
> timer etc.
>
> Is there any standard thing in u-boot that looks at these to "do
> stuff" e.g. to put peripherals through a manual reset or skip certain
> parts of init.
>
> Is there any standard way of getting this to the Linux kernel and
> ultimately to userspace to generate a log?
>
> Searching for "linux reboot reason" naturally leads to a zillion
> results of people wanting to know why their server/laptop crashed so
> my duckduckgo-fu (yeah I'm trying to make that a thing) is failing me.
>

One lead I did find was that it looks like the keymile kmp204x
board(s) read this info out of the RSTRQSR register and stashes it
into a FPGA register. Not sure if this just drives a LED or if there's
something else that reads this info back later.