On 15/06/2022 11:13, 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 That I did not propose. :) We have a binding for regulator supplies so you do no need a new one. > 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. DTS and bindings describe here the hardware, so focus on that. Device is supplied by some regulator which I assume can be controlled by GPIO. I don't think you need new bindings for that. Implementation of bindings, so Linux driver, is different thing. > >>> We are really trying to model something where a single GPIO pin (via a GPIO regulator or whatever) can >>> control >>> power to a variety of on-board peripherals. And, of course, we envision runtime PM actually making use of >>> it >>> e.g. when doing suspend/resume. >> >> And this GPIO pin controls what? Some power switch which cuts the power >> of one regulator or many? > > Well, that doesn't really matter. Resp. this part one should be able to sufficiently model using whatever > available regulator lore we already have (e.g. whatever delays/times). > >> If many different regulators, how do you >> handle small differences in ramp up time? > > Well, I don't think this is any different to any other regulator(s), not? Them HW folks will just need to tell > us some reasonable numbers for those delays/times. Probably... I just wonder how that would work in practice. Best regards, Krzysztof
