Am 05.05.2019 um 22:17 schrieb Marek Vasut:
On 5/5/19 8:05 AM, Simon Goldschmidt wrote:
On 05.05.19 03:42, Marek Vasut wrote:
On 5/4/19 9:10 PM, Simon Goldschmidt wrote:
Am 04.05.2019 um 20:43 schrieb Marek Vasut:
On 5/3/19 10:53 PM, Simon Goldschmidt wrote:
Marek Vasut <ma...@denx.de <mailto:ma...@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.goldschm...@gmail.com
<mailto:simon.k.r.goldschm...@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.
If Linux switches the chip into some weird mode the bootrom cannot cope
with, it's a reset routing problem. This cannot be fixed in software.
No, it cannot be fixed, but currently there's a workaround for those
boards and I thought it was worth to keep this workaround, even though
my own boards will be fixed and not require such a workaround in the
future :-)
What's the workaround ?
The workaround is what this patch is about: the Boot ROM just branches
off to SRAM where it expectes SPL to be still working.
SPL can then e.g. reset 4-byte mode or whatever to still communicate
with the device when Boot ROM can't.
Of course the downside is that SRAM might be overwritten meanwhile,
which is why it's a workaround only, not the best idea how to do things...
Regards,
Simon
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