[PATCH 9/9] ARM: ux500: always select ABX500_CORE

[Linus Walleij]

On Fri, May 3, 2013 at 2:48 PM, Arnd Bergmann <arnd at arndb.de> wrote:

> I think we can certainly eliminate the ABX500 option, this one can
> just get selected by AB3100 and AB8500. The PRCMU can also
> be silent because as you say it is always needed.

OK sounds like a plan.

> The GPADC driver is interesting: it does not have its own user
> interface (besides the debugging driver) and could just get selected
> by the other drivers using its exported interfaces. It would
> also be better to convert it to the standard IIO ADC interface,
> but I don't know if that's realistic.

This should be moved over to IIO ADC, that subsystem however
did not exist when this driver was submitted, that is why it ended
up in MFD. As usual someone needs to go hack on it...

> This leavs the debugging
> interface as the only sub-option. Do you know if that is
> actually being used by developers, or is this one of those interfaces
> that were created during bringup and then never touched again
> after everything worked?

Something like that, but as long as new platforms using that
ASIC is coming out it remains quite usable for this.

It is also used for hardware validation, where you hook up the
system with a lot of electric probes and want to set specific
bits here and there to validate functionality. There just a minor
change to the silicon or packaging triggers such re-validation.

The usecase is similar to the debug interface we invented for
pin control recently, however there we managed to make things
centralized.

> Regarding AB3100, I assume the relationship to U300 is similar to
> that between DB8500 and AB8500. Are you able to boot a U300 system
> without touching AB3100?

I would say no. The system will be in some bootstrap state unless
you bring up the AB3100, and especially the regulators.

These are default y but should arguably be selected y
instead.

The U300 SoC will bootstrap power in a strange way until the
regulators are up, and then hand over to software-controlled
regulators for powering the SoC and release that bootstrap.

This is not harmful but a very strange and it's doubtful whether
I would call that "fully booted". It's something like booting
into "safe mode"
http://en.wikipedia.org/wiki/Safe_mode

Not enabling regulators on the U300 will have other strange
effects ... like MMC/SD not working. Yet we can not have
depends on REGULATORS in the Kconfig for the MMCI driver
since this driver is also used on systems without the regulator
framework (hardwired power).

All these run-time "makes sense" is in a bit of flux as compared
to config-and-compile-time "makes sense" unfortunately.

I lean toward selecting AB3100 and REGULATOR_AB3100
for the U300 actually.

Yours,
Linus Walleij