[U-Boot] [PATCH 5/5] arm: socfpga: implement proper peripheral reset

[Simon Goldschmidt]

On Mon, Jan 28, 2019 at 12:30 PM Marek Vasut <marex at denx.de> wrote:
>
> On 1/27/19 9:56 AM, Simon Goldschmidt wrote:
> > Am 26.01.2019 um 10:00 schrieb Marek Vasut:
> >> On 1/25/19 9:30 PM, Simon Goldschmidt wrote:
> >>> This commit removes ad-hoc reset handling for peripheral resets from SPL
> >>> for socfpga gen5.
> >>>
> >>> This is done because as U-Boot drivers support reset handling by now.
> >>>
> >>> For kernels that don't support taking peripherals out of reset that are
> >>> not enabled by U-Boot, a new Kconfig option "OLD_SOCFPGA_KERNEL_COMPAT"
> >>> is added, which keeps the old behaviour of just enabling all
> >>> peripherals.
> >>>
> >>> This new option is enabled by default for now, as even Linux 4.20 does
> >>> not support reset handling on all peripherals.
> >>>
> >>> Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt at gmail.com>
> >>
> >> Well ew, don't we have some pre-linux-boot hook which could just flip
> >> the reset register bits in one place ? And also, I'd prefer this to be
> >> runtime-configurable, not compile-time configurable.
> >
> >
> > And this will be the biggest change for v2. It's also why I needed so
> > long to send this series. What I sent in this version is how Tom said
> > the same thing is being handled for mach-sunxi (Kconfig
> > "OLD_SUNXI_KERNEL_COMPAT").
> >
> > So if I remember your last mails about this topic, you'd prefer an
> > environment variable with a callback that leads to enabling all
> > peripherals just before jumping to Linux (yes, I'll find a hook for that).
>
> Rather, I'd prefer some .remove() code in the SoCFPGA reset driver which
> would check an environment variable to determine whether it should
> ungate the resets before booting Linux or not.

OK, that should work. I'll work on that for v2.

Regards,
Simon

>
> > I see two problems here:
> > - enabling all peripherals will need to be the default for some time,
> > until Linux supports reset handling in all drivers. How do you want to
> > deal with that?
>
> Set the env variable to default=1 for all socfpga boards ?
>
> > - is this scheme used somewhere else for compatibility? I think it would
> > make sense for multiple architectures to use the same way to handle such
> > compatibility issues...
>
> I don't think so, however it's better than compile-time setting.
>
> [...]
>
> --
> Best regards,
> Marek Vasut