Re: [PATCH 2/2] clk: clps711x: Add DT bindings documentation

Alexander Shiyan
2014-06-02T09:32:48Z

Mon, 2 Jun 2014 09:56:51 +0100 ?? Mark Rutland <mark.rutland@arm.com>:
> On Sun, Jun 01, 2014 at 10:55:22AM +0100, Alexander Shiyan wrote:
> > This patch adds DT binding documentation for the Cirrus Logic
> > CLPS711X-based CPUs clock subsystem.
> >
> > Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
> > ---
> > .../devicetree/bindings/clock/clps711x-clock.txt | 19 +++++++++++++++++++
> > 1 file changed, 19 insertions(+)
> > create mode 100644 Documentation/devicetree/bindings/clock/clps711x-clock.txt
> >
> > diff --git a/Documentation/devicetree/bindings/clock/clps711x-clock.txt b/Documentation/devicetree/bindings/clock/clps711x-clock.txt
> > new file mode 100644
> > index 0000000..0fdf3c9
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/clock/clps711x-clock.txt
> > @@ -0,0 +1,19 @@
> > +* Clock bindings for the Cirrus Logic CLPS711X CPUs
> > +
> > +Required properties:
> > +- compatible : Shall contain "cirrus,clps711x-clk".
> > +- reg : Address of the internal register set.
> > +- cpufreq : Factory set default frequency in HZ.
>
> Huh? Why is this called "cpufreq" what is this the frequency of,
> exactly?
>
> Is this an input or an output?

Modern CLPS711X CPUs support PLL reprogramming, while for older processors,
this procedure is not possible and the CPU clock is set to a fixed value. Thus if the
value of the PLL multiplier is not correct (missing), we use a fixed CPU frequency
of the processor, described in DT, which allows us to use the driver for the new and
old versions of this CPU.

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