linux-kernel - Re: [RFC PATCH 0/2] Add software node support to regulator framework

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Date:   Tue, 13 Jul 2021 22:46:29 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     Daniel Scally <djrscally@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <mgross@...ux.intel.com>,
        Maximilian Luz <luzmaximilian@...il.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        kieran.bingham@...asonboard.com
Subject: Re: [RFC PATCH 0/2] Add software node support to regulator framework

On Tue, Jul 13, 2021 at 9:19 PM Mark Brown <broonie@...nel.org> wrote:
>
> On Tue, Jul 13, 2021 at 06:55:59PM +0300, Andy Shevchenko wrote:
> > On Tue, Jul 13, 2021 at 6:25 PM Mark Brown <broonie@...nel.org> wrote:
>
> > > The driver code is trivial boilerplate, assuming someone doesn't go and
> > > implement a helper to register stuff separately like I suggested.  The
> > > proposed swnode stuff would involve duplicating the DT parsing code.
> > > This seems like a whole lot of effort for something that provides a
> > > worse result than either of the existing things.
>
> > I'm not sure I follow. Where did you see the duplication when I saw
> > the other way around?
>
> The current patch consists entirely of additions, it does not remove any
> existing code at all, the diffstat is:
>
>  5 files changed, 174 insertions(+)

Ah, okay, you are talking with regard to the current patch. I talked
in generic terms.

> > Converting code from OF to fwnode APIs in most cases is smooth and
> > doesn't add any overhead to the codebase,
>
> We explicitly do not want to attempt to parse regulator properties out
> of ACPI platform descriptions because using the regulator binding on
> ACPI platforms conflicts with the ACPI model for power management and
> we really don't want to encourage platforms to attempt to mix and match
> here, it's not going to lead to anything robust.  System integrators
> that need this sort of OS visible low level power management really
> should be working with the UEFI forum to get an ACPI specification for
> it, or if they don't really need it fixing up their AML to DTRT.

No-one is objecting to this. I agree that integration of regulators
and ACPI should be done in a specific way if needed at all.

> If you were to say that we could bodge around that by somehow forcing
> this binding to exist only for swnodes when running on ACPI systems then
> we'd still have the problems with creating something with worse tooling
> than what's there already.

Of course, no objections to this.

> Like I said in the other mail fwnode is a nice hack for systems that are
> using ACPI but have hardware that's doing something totally outside the
> ACPI model to allow them to reuse work that's been done for DT, it's not
> a universal solution to the lack of appropriate support for describing
> modern systems in ACPI.

In some (I suppose rear) cases it may be used by DT-enabled platforms as well.
I can imagine the case when you have a system in ROM and only what you
can do to change DTB there is either use DT overlays (which seems to
be not working, plenty of gaps there according to a Wiki I saw once)
or do something in the board files.

So, if you replace "ACPI" with the "firmware resource provider" in the
above paragraph, I will agree 100% with you.

-- 
With Best Regards,
Andy Shevchenko