Re: [PATCH v1 0/5] power: domain: Add driver for a PM domain provider which controls

[Dmitry Baryshkov]

On 15/06/2022 21:13, Marcel Ziswiler wrote:
> On Wed, 2022-06-15 at 10:37 -0700, Krzysztof Kozlowski wrote:
> > On 15/06/2022 10:31, Marcel Ziswiler wrote:
> > > Hi
> > >
> > > On Wed, 2022-06-15 at 10:15 -0700, Krzysztof Kozlowski wrote:
> > > > On 15/06/2022 09:10, Max Krummenacher wrote:
> > > > > Hi
> > > > >
> > > > > On Tue, Jun 14, 2022 at 9:22 AM Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote:
> > > > > > Hi Rob,
> > > > > >
> > > > > > On Mon, Jun 13, 2022 at 9:15 PM Rob Herring <robh@xxxxxxxxxx> wrote:
> > > > > > > On Thu, Jun 09, 2022 at 05:08:46PM +0200, Max Krummenacher wrote:
> > > > > > > > From: Max Krummenacher <max.krummenacher@xxxxxxxxxxx>
> > > > > > > >
> > > > > > > > its power enable by using a regulator.
> > > > > > > >
> > > > > > > > The currently implemented PM domain providers are all specific to
> > > > > > > > a particular system on chip.
> > > > > > >
> > > > > > > Yes, power domains tend to be specific to an SoC... 'power-domains' is
> > > > > > > supposed to be power islands in a chip. Linux 'PM domains' can be
> > > > > > > anything...
> > > > >
> > > > > I don't see why such power islands should be restricted to a SoC. You can
> > > > > build the exact same idea on a PCB or even more modular designs.
> > > >
> > > > In the SoC these power islands are more-or-less defined. These are real
> > > > regions gated by some control knob.
> > > >
> > > > Calling few devices on a board "power domain" does not make it a power
> > > > domain. There is no grouping, there is no control knob.
> > > >
> > > > Aren't you now re-implementing regulator supplies? How is this different
> > > > than existing supplies?
> > >
> > > I believe the biggest difference between power-domains and regulator-supplies lays in the former being
> > > driver
> > > agnostic while the later is driver specific.
> >
> > That's one way to look, but the other way (matching the bindings
> > purpose) is to look at hardware. You have physical wire / voltage rail
> > supply - use regulator supply. In the terms of the hardware - what is
> > that power domain? It's a concept, not a physical object.
>
> Well, but how can that concept then exist within the SoC but not outside? I don't get it. Isn't it just the
> exact same physical power gating thingy whether inside the SoC or on a PCB?
>
> > > Meaning with power-domains one can just add such arbitrary
> > > structure to the device tree without any further driver specific changes/handling required. While with
> > > regulator-supplies each and every driver actually needs to have driver specific handling thereof added. Or
> > > do I
> > > miss anything?
> >
> > Thanks for clarification but I am not sure if it matches the purpose of
> > bindings and DTS. You can change the implementation as well to have
> > implicit regulators. No need for new bindings for that.
>
> Okay, maybe that would also work, of course. So basically add a new binding which allows adding regulators to
> arbitrary nodes which then will be generically handled by e.g. runtime PM. Almost something like assigned-
> clocks [1] you mean? I guess that could work. Remember that's why Max posted it as an RFC to get such feedback.
> Thanks for further refining those ideas.

Please do not do this. You have an external device. It has some input 
voltage rails. Please define -supply properties for each of the voltage 
rails. Explicitly power them on and off. Use fixed-regulator for your 
GPIO regulators. Other boards might have other ways to control the power 
supply.

Then define the pm_runtime callbacks doing proper work for you. If you 
wish to do the magic, consider looking on the pm_clock.h interface (and 
adding the pm_regulators.h). But this approach can also be frowned upon 
by the PM maintainers. Nevertheless, this is the driver/core issue. The 
DT interface should be the same: a set of regulators and a set of 
-supply properties.

--
With best wishes
Dmitry