[U-Boot] [PATCH] arm: socfpga: control reboot from SRAM via env callback

[Simon Goldschmidt]

Am 04.05.2019 um 20:43 schrieb Marek Vasut:
> On 5/3/19 10:53 PM, Simon Goldschmidt wrote:
>>
>>
>> Marek Vasut <marex at denx.de <mailto:marex at denx.de>> schrieb am Fr., 3.
>> Mai 2019, 22:42:
>>
>>      On 5/3/19 10:39 PM, Simon Goldschmidt wrote:
>>      >
>>      >
>>      > On 03.05.19 22:35, Marek Vasut wrote:
>>      >> On 5/3/19 10:30 PM, Simon Goldschmidt wrote:
>>      >>>
>>      >>>
>>      >>> On 03.05.19 22:28, Marek Vasut wrote:
>>      >>>> On 5/3/19 10:08 PM, Simon Goldschmidt wrote:
>>      >>>>> This moves the code that enables the Boot ROM to just jump to SRAM
>>      >>>>> instead
>>      >>>>> of loading SPL from the original boot source on warm reboot.
>>      >>>>>
>>      >>>>> Instead of always enabling this, an environment callback for the
>>      >>>>> env var
>>      >>>>> "socfpga_reboot_from_sram" is used. This way, the behaviour can be
>>      >>>>> enabled
>>      >>>>> at runtime and via saved environment.
>>      >>>>>
>>      >>>>> Signed-off-by: Simon Goldschmidt
>>      <simon.k.r.goldschmidt at gmail.com
>>      <mailto:simon.k.r.goldschmidt at gmail.com>>
>>      >>>>
>>      >>>> Would that be like a default "reset" command action ?
>>      >>>> This probably shouldn't be socfpga specific then.
>>      >>>
>>      >>> No, it's a thing that lives on and influences even the soft
>>      reset issued
>>      >>> by linux "reboot" command. This is something *very* socfpga
>>      specific.
>>      >>
>>      >> Hmmm, so isn't this a policy to be configured on the Linux end ?
>>      >
>>      > Might be, but it affects U-Boot's 'reset' command as well. And I guess
>>      > it's set up in U-Boot this early to ensure it always works.
>>
>>      Drat, that's right. So there has to be some way to agree on how the
>>      reset works between the kernel and U-Boot ?
>>
>>      > If it were for me, we could drop writing this magic altogether. I just
>>      > figured some boards might require it to be written somewhere, and came
>>      > up with a patch that might save those boards with the way it was
>>      before.
>>
>>      Isn't this magic actually used by bootrom ?
>>
>>
>> Right. It tells the boot rom to jump to ocram on next reboot instead of
>> loading spl from qspi or mmc. But if that's required or not a good idea
>> at all depends on many factors. Some of them board related, some U-Boot
>> related and some Linux related (depending on the hardware and drivers used).
> 
> Should that be runtime configurable then ?

Since it might depend on Linux putting the qspi chip into a state where 
it's not accessible by the boot ROM. That might change without 
rebuilding U-Boot.

On the other hand, this is probably more of a U-Boot build time config. 
I could make it a Kconfig option as well...

Regards,
Simon