[U-Boot] Passing information from SPL to next stage

[Chris Packham]

On Tue, Jul 26, 2016 at 2:51 AM, Tom Rini <trini at konsulko.com> wrote:
> On Mon, Jul 25, 2016 at 08:54:27PM +1200, Chris Packham wrote:
>
>> Hi,
>>
>> Is there a standard way of passing information discovered by the SPL
>> onto the next boot stage?
>>
>> I'm guessing for platforms that support the new driver model it's
>> possible to add/update information in the device-tree, but what about
>> platforms that don't currently use the new driver model.
>>
>> I had a quick search of the mailing list and docs but didn't find
>> anything obvious. If I've missed something feel free to point me at
>> it.
>
> Just how much information is it?  The answer is somewhere between
> 'save_boot_params' (shove a tiny bit of data in a magic location) and
> "switch to driver model, whack the DT prior to kicking off U-Boot",
> depending also on size constraints.
>

In our particular use-case we want to check for a specific input
character in SPL to launch a RAM test, otherwise proceed to a full
boot and possibly launch other diagnostics based on a different key.
The main point is we only want to call getc() once so the information
on what input character was received (or the result of interpreting
it) needs to go from SPL to the next stage if the input wasn't
something that the SPL cared about.

I'll take a look at save_boot_params.