Re: [RFC v4 01/14] regulator: of: Add helper for getting all supplies

[Rob Herring]

On Thu, Jun 09, 2016 at 01:42:02PM +0200, Krzysztof Kozlowski wrote:
> On 06/09/2016 12:29 PM, Mark Brown wrote:
> > On Thu, Jun 09, 2016 at 11:44:18AM +0200, Krzysztof Kozlowski wrote:
> >> Few drivers have a need of getting regulator supplies without knowing
> >> their names:
> >> 1. The Simple Framebuffer driver works on setup provided by bootloader
> >>    (outside of scope of kernel);
> >> 2. Generic power sequence driver may be attached to any device node.
> >>
> >> Add a Device Tree helper for parsing "-supply" properties and returning
> >> allocated bulk regulator consumers.
> > 
> > I'm still very concerned that this is just an invitation to people to
> > write half baked regulator consumers and half baked DTs to go along with
> > it, making it a standard API that doesn't have big red flags on it that
> > will flag up when "normal" drivers use it is not good.  Right now this
> > just looks like a standard API and people are going to just start using
> > it.  If we are going to do this perhaps we need a separate header or
> > something to help flag this up.
> 
> No problem, I can move it to a special header.  Actually, if you dislike
> this as an API, it does not have to be in header at all.  I can just
> duplicate the simplefb code.
> 
> > In the case of power sequences I'd expect the sequences to perform
> > operations on named supplies - the core shouldn't know what the supplies
> > are but the thing specifying the sequence should.
> 
> Hm, so maybe passing names like:
> 
> usb3503@08 {
> 	reset-gpios = <&gpx3 5 GPIO_ACTIVE_HIGH>;
> 	initial-mode = <1>;
> 	vdd-supply = <&buck8_reg>;
> 	foo-supply = <&buck9_reg>;
> 
>         power-sequence;
> 	power-sequence-supplies = "vdd", "foo";

This alone would be fine as it is just one property, but then what's 
next? power-sequence-delay, power-sequence-clocks, etc. What if you 
need to express ordering relationship of supplies, clocks, gpios? We end 
up with a scripting language in DT and we don't want to have that.

Rob