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

[Chris Packham]

On Tue, Jul 26, 2016 at 11:51 AM, Chris Packham <judge.packham at gmail.com> wrote:
> 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.

Oh and I neglected to mention this board is based on the Freescale/NXP
T2081 so save_boot_params looks a little too ARM specific to be
helpful.