linux-kernel - Re: [PATCH v4 1/2] dt: cpufreq: st: Provide bindings for ST's CPUFreq implementation

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Message-ID: <20150728074104.GL21114@x1>
Date:	Tue, 28 Jul 2015 08:41:04 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	kernel@...inux.com, rjw@...ysocki.net, linux-pm@...r.kernel.org,
	devicetree@...r.kernel.org, ajitpal.singh@...com, sre@...nel.org,
	dbaryshkov@...il.com
Subject: Re: [PATCH v4 1/2] dt: cpufreq: st: Provide bindings for ST's
 CPUFreq implementation

On Tue, 28 Jul 2015, Viresh Kumar wrote:

> On 27-07-15, 16:20, Lee Jones wrote:
> > Cc: devicetree@...r.kernel.org
> > Signed-off-by: Lee Jones <lee.jones@...aro.org>
> > ---
> > 
> > Changelog:
> >  - Using OPP-v2
> >  - Moved (and linked) a bunch of documentation to ../power/
> > 
> >  .../devicetree/bindings/cpufreq/cpufreq-st.txt     | 40 ++++++++++++++++++++++
> >  1 file changed, 40 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/cpufreq/cpufreq-st.txt
> > 
> > diff --git a/Documentation/devicetree/bindings/cpufreq/cpufreq-st.txt b/Documentation/devicetree/bindings/cpufreq/cpufreq-st.txt
> > new file mode 100644
> > index 0000000..79add9d
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/cpufreq/cpufreq-st.txt
> > @@ -0,0 +1,40 @@
> > +Binding for ST's CPUFreq driver
> > +===============================
> > +
> > +Frequency Scaling only
> > +----------------------
> > +
> > +Located in CPU's node:
> > +
> > +- operating-points		: [See: ../power/opp.txt]
> > +
> > +Example [safe]
> > +--------------
> > +
> > +cpus {
> > +	cpu@0 {
> > +				 /* kHz     uV   */
> > +		operating-points = <1500000 0
> > +				    1200000 0
> > +				    800000  0
> > +				    500000  0>;
> > +	};
> > +};
> > +
> > +Dynamic Voltage and Frequency Scaling (DVFS)
> > +--------------------------------------------
> > +
> > +Located in CPU's node:
> > +
> > +- operating-points-v2-sti	: [See ../power/opp-st.txt]
> > +
> > +Example [unsafe]
> > +----------------
> > +
> > +cpus {
> > +	cpu@0 {
> > +		operating-points-v2	= <[OPP list phandle]>;
> > +	};
> > +};
> > +
> > +For an example of an OPP list, see ../power/opp-st.txt.
> 
> I don't think you need this file/patch at all.. It is almost blank and
> doesn't define a binding. And so there is no need to specify this at
> all. Just an OPP binding file is enough.

I have two issues with that.  Firstly, although the driver uses the
OPP API (it also uses the Regulator and Clock API too), it is
fundamentally a CPUFreq driver, so I think it should have a CPUFreq
DT entry.  Secondly, if someone doesn't know the history of the
ST CPUFreq set, they will look here for an accompanying document.  I
personally wouldn't think to look in power/*opp* for a CPUFreq
binding.

Perhaps, as all of the CPUFreq drivers use the OPP API, everything
should be moved to drivers/base/power or drivers/power?

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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