Am Freitag, 10. Juni 2016, 12:30:56 schrieb Rob Herring:

On Thu, Jun 09, 2016 at 01:42:02PM +0200, Krzysztof Kozlowski wrote:

quoted

On 06/09/2016 12:29 PM, Mark Brown wrote:

quoted

On Thu, Jun 09, 2016 at 11:44:18AM +0200, Krzysztof Kozlowski wrote:

quoted

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.

quoted

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.

Also, at least from the simple blocks I've seen so far (usb-hub chips, usb-
sata bridges), a power-supply feels more like it should be a regular phy-
supply of the usbphy connected the the host-controller.

It's similar for mmc-controllers where vmmc-supply on the controller handles 
the power-supply of the connected card and thus the current mmc power-
sequences do not handle regulators.

Reset-gpios and clock inputs are clearly properties of the actual device, but 
the supply control should probably lay with the host controller, especially as 
it is the one deciding when to power on/off things.