Re: [PATCH RFC 2/3] power: mxs_power: add driver for mxs power subsystem

[Stefan Wahren <stefan.wahren@i2se.com>]

Hi Mark,

> Mark Brown <broonie@kernel.org> hat am 27. Januar 2015 um 01:16 geschrieben:
>
>
> On Mon, Jan 26, 2015 at 08:46:45PM +0100, Stefan Wahren wrote:
>
> > > > Does a common property name exists for the switching frequency or would
> > > > it be vendor specific?
>
> > > As far as I know most regulators have fixed switching frequencies,
> > > so there is no common property name so far. I added regulator
> > > framework people, since this property should be regulator specific.
>
> No, it's pretty common for there to be a couple of options - there's
> normally a performance tradeoff (power for regulation accuracy and/or
> cost) which can be selected. IIRC it's selected at design time as it
> affect the choice of passives on the board.
>
> > okay i understand. But doesn't it need a extra driver to set the switching
> > frequency because of the new compatible string?
>
> I don't understand this bit at all, sorry.

Sebastian suggested a new sub-node in the devicetree:

    powerpll {
        compatible = "fsl,imx28-power-pll"
        #clock-cells = <0>;
        clock-frequency = <12345>;
    }

and i think that the new compatible string needs a separate driver to take care
of the switching frequency.

Or is it okay to leave the handling of the switching frequency in the mxs-power
driver?

Btw if we add a new node to set switching frequency, i think it would be better
to describe the dc-dc convertor and not the pll:

    dcdc {
       compatible = "fsl,imx28-dcdc"
       frequency = <12345>;
    }

What do you think?

Best regards
Stefan

>
> >
> > At this point i think about moving this feature into the bootloader.
> >
> > @Fabio, @Marek:
> >
> > What's your opinion about that?
> >
> > >
> > > -- Sebastian
> >
> > Stefan
> >