Re: [PATCH] ARM: dts: imx7ulp: Add cpu clock-frequency property

Shawn Guo
2019-12-04T02:02:48Z

+ Vincent

On Tue, Dec 03, 2019 at 01:09:22AM +0000, Anson Huang wrote:
>
> > Subject: Re: [PATCH] ARM: dts: imx7ulp: Add cpu clock-frequency property
> >
> > On Tue, Nov 05, 2019 at 09:49:38AM +0800, Anson Huang wrote:
> > > Add "clock-frequency" property to avoid below warning on i.MX7ULP:
> > >
> > > [ 0.011762] /cpus/cpu@0 missing clock-frequency property
> > >
> > > Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
> > > ---
> > > arch/arm/boot/dts/imx7ulp.dtsi | 1 +
> > > 1 file changed, 1 insertion(+)
> > >
> > > diff --git a/arch/arm/boot/dts/imx7ulp.dtsi
> > > b/arch/arm/boot/dts/imx7ulp.dtsi index d37a192..87b2237 100644
> > > --- a/arch/arm/boot/dts/imx7ulp.dtsi
> > > +++ b/arch/arm/boot/dts/imx7ulp.dtsi
> > > @@ -41,6 +41,7 @@
> > > compatible = "arm,cortex-a7";
> > > device_type = "cpu";
> > > reg = <0>;
> > > + clock-frequency = <500210526>;
> >
> > I cannot find the binding doc for this property. What is the definition of it,
> > the maximum frequency that the cpu could possibly run at?
>
>
> The code is as below, maybe the property is missing from the beginning of this code,
> this property should mean the current frequency of CPU running at I think:
>
> arch/arm/kernel/topology.c
>
> 122 rate = of_get_property(cn, "clock-frequency", &len);
> 123 if (!rate || len != 4) {
> 124 pr_err("%pOF missing clock-frequency property\n", cn);
> 125 continue;
> 126 }

Yes, I can find the code, but not bindings for it. Considering
frequency of a CPU can be scaled in a quite wide range, we need
a clear understanding on this property. IIUIC, the property is used to
calculate the capacity of CPU, it should be the maximum frequency the
CPU could possibly scale to?

Shawn