Date:	Mon, 29 Sep 2014 15:10:07 +0200
From:	Stefan Wahren <stefan.wahren@...e.com>
To:	Mark Rutland <mark.rutland@....com>
CC:	"lgirdwood@...il.com" <lgirdwood@...il.com>,
	"broonie@...nel.org" <broonie@...nel.org>,
	"shawn.guo@...aro.org" <shawn.guo@...aro.org>,
	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	Pawel Moll <Pawel.Moll@....com>,
	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	"galak@...eaurora.org" <galak@...eaurora.org>,
	"festevam@...il.com" <festevam@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"kernel@...gutronix.de" <kernel@...gutronix.de>
Subject: Re: [PATCH 1/2] DT: add binding for mxs regulator

Hi,

Am 29.09.2014 um 14:41 schrieb Mark Rutland:
> Well, the simple-bus will cause the children to be probed. But it looks
> like you care about properties of the parent. I don't think that
> simple-bus is appropriate because it's not being handled as a
> transparent bridge from the PoV of the children.

actually i need the address of the power status register. In this
version i get the base address from the parent node add an offset.

Do you prefer to define the address of the power status register like a
second address cell:

reg_vddd: regulator@...44040 {
	reg = <0x80044040 0x10
	       0x800440c0 0x01>;
        ...
};

or do i need special properties like this:

reg_vddd: regulator@...44040 {
	reg = <0x80044040 0x10>;
	fsl,mxs-status-reg = <0x800440c0>;
        ...
};

>> Do we need a extra driver?
> Perhaps, but it's relatively simple to match on a compatible string and
> probe children if you just wantto start small for now.

Okay. Would be great if someone has a good example. At first, i thought
of power/anatop.

>
>>>> +- #address-cells: Number of cells required to define regulator register,
>>>> +  must be 1
>>>> +- #size-cells: Number of cells required to define register size, must be 1
>>> Why must this be the case, given that the child node expects an absolute
>>> physical address?
>> I need a property to define the control register for the regulators
>> without defining vendor specific properties like "fsl,mxs-control-reg"
>> or something.
> You misunderstand me. I was querying the "must be 1" rather than the
> proeprties themselves.
>
>>> What's wrong with #address-cells = <2>, for example?
>> Nothing
> Then we shouldn't specify "must be 1", no?

Right, must be at least 1.

>>>> +- reg: Absolute physical address and size of the register set for the device
>>> Why is this here _and_ in the child node(s)?
>> The parent of the power node is also a simple bus. I use this to
>> calculate the power status register per offset.
>>
>>> What is the difference between this node and its children?
>> The parent node represent the power sub system and the regulators are
>> part of this sub system.
>>
>>> Can there be more than one sub-node?
>> In the i.MX28 are at least 4 voltage regulators, 1 current regulator and
>> many more. At first, the driver should implement only 3 voltage
>> regulators (vddd, vdda, vddio).
> Ok.
>
> I think you need a binding for the power subsystem, and a trivial driver
> that can match on that and probe the child regulators. Are there
> components other than voltage or current regulators in the sub system?

Yes, according to the reference manual there is a dc-dc converter, a
battery charger, battery monitor, ...

In short a lot of developing time ;-)

> Mark.

Best regards

Stefan

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