[PATCH 6/8] power: domain: apple: Add reset support

[Simon Glass]

Hi Mark,

On Sat, 22 Jan 2022 at 07:12, Mark Kettenis <mark.kettenis at xs4all.nl> wrote:
>
> > From: Simon Glass <sjg at chromium.org>
> > Date: Fri, 21 Jan 2022 18:40:23 -0700
> >
> > Hi Mark,
> >
> > On Fri, 14 Jan 2022 at 04:05, Mark Kettenis <kettenis at openbsd.org> wrote:
> > >
> > > The power management controller found on Apple SoCs als provides
> > > a way to reset all devices within a power domain. This is needed
> > > to cleanly shutdown the NVMe controller before we hand over
> > > control to the OS.
> > >
> > > Signed-off-by: Mark Kettenis <kettenis at openbsd.org>
> > > ---
> > >  arch/arm/Kconfig                  |  1 +
> > >  drivers/power/domain/apple-pmgr.c | 73 ++++++++++++++++++++++++++++++-
> > >  2 files changed, 73 insertions(+), 1 deletion(-)
> >
> > This should use devicetree instead of device_bind() and be a reset
> > driver in drivers/reset
>
> Not sure what you mean with "this should use devicetree".  The reset
> and power domain functionality is integrated in the same hardware
> register and there is a single node that decsribes the device.
>
> The Linux driver implements the power domain and reset functionality
> in a single driver as well.  I suppose I could move the reset code
> into a file of its own in drivers/reset, but I don't think it would
> make the code easier to understand.  And I'd still need to bind the
> reset driver explicitly in apple_pmgr_probe() as it isn't possible to
> automatically bind two drivers to a single device tree node as far as
> I can tell.

It seems odd that Linux does this sort of thing. The normal U-Boot
approach would be to create a parent MFD driver with children for each
uclass. Does linux do that these days?

Driver model cannot create two drivers from one device tree node,
although you can create one manually later as you have done.

It seems OK to follow along with Linux, if it makes it easier to
maintain. Otherwise, drivers/reset would be better for the reset
driver.

Either way:

Reviewed-by: Simon Glass <sjg at chromium.org>
Tested on: Macbook Air M1
Tested-by: Simon Glass <sjg at chromium.org>

Regards,
Simon