[1/3] DT Binding for omap3 temperature sensor

OMAP34xx and OMAP36xx processors contain a register in the syscon area,
which can be used to determine the SoCs temperature. This provides a
DT binding specification for the temperature monitor.

Signed-off-by: Sebastian Reichel <sre@kernel.org>
---
 .../bindings/hwmon/omap3-temperature.txt           | 25 ++++++++++++++++++++++
 1 file changed, 25 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/omap3-temperature.txt

On Fri 2014-12-26 13:34:52, Sebastian Reichel wrote:
> OMAP34xx and OMAP36xx processors contain a register in the syscon area,
> which can be used to determine the SoCs temperature. This provides a
> DT binding specification for the temperature monitor.
> 
> Signed-off-by: Sebastian Reichel <sre@kernel.org>
> ---
>  .../bindings/hwmon/omap3-temperature.txt           | 25 ++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/hwmon/omap3-temperature.txt
> 
> diff --git a/Documentation/devicetree/bindings/hwmon/omap3-temperature.txt b/Documentation/devicetree/bindings/hwmon/omap3-temperature.txt
> new file mode 100644
> index 0000000..99631ad
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/hwmon/omap3-temperature.txt
> @@ -0,0 +1,25 @@
> +* OMAP3 temperature sensor
> +
> +The OMAP34xx and OMAP36xx processors contain a register in the syscon area,
> +which can be used to determine the SoCs temperature.
> +
> +Requires node properties:
> +- compatible :	should contain one of
> +	- "ti,omap34xx-temperature-sensor" for OMAP34xx
> +	- "ti,omap36xx-temperature-sensor" for OMAP36xx
> +- syscon :	Should be a phandle to system configuration node which
> +		encompases the temperature register
> +- clocks :	Should contain 32KHz fclk clock specifier
> +- clock-names :	Should contain clock names
> +	- "fck" for the 32KHz fclk clock specifier

I don't quite get it. The temperature sensor is internal on the CPU,
right? Why do we need device tree to describe it? As soon as we have
CPU that is compatible to ti,omap3430, we know everything we need to
know, no?

> +Example for omap34xx:
> +
> +/ {
> +	temperature-sensor {
> +		compatible = "ti,omap34xx-temperature-sensor";
> +		syscon = <&omap3_scm_general>;
> +		clocks = <&ts_fck>;
> +		clock-names = "fck";
> +	};
> +};

Or is there something that depends on the board there? Or do we want
to do it like this to be consistent with existing bindings?

									Pavel

Hi Pavel,

On Fri, Dec 26, 2014 at 06:19:44PM +0100, Pavel Machek wrote:
> On Fri 2014-12-26 13:34:52, Sebastian Reichel wrote:
> > OMAP34xx and OMAP36xx processors contain a register in the syscon area,
> > which can be used to determine the SoCs temperature. This provides a
> > DT binding specification for the temperature monitor.
> > 
> > Signed-off-by: Sebastian Reichel <sre@kernel.org>
> > ---
> >  .../bindings/hwmon/omap3-temperature.txt           | 25 ++++++++++++++++++++++
> >  1 file changed, 25 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/hwmon/omap3-temperature.txt
> > 
> > diff --git a/Documentation/devicetree/bindings/hwmon/omap3-temperature.txt b/Documentation/devicetree/bindings/hwmon/omap3-temperature.txt
> > new file mode 100644
> > index 0000000..99631ad
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/hwmon/omap3-temperature.txt
> > @@ -0,0 +1,25 @@
> > +* OMAP3 temperature sensor
> > +
> > +The OMAP34xx and OMAP36xx processors contain a register in the syscon area,
> > +which can be used to determine the SoCs temperature.
> > +
> > +Requires node properties:
> > +- compatible :	should contain one of
> > +	- "ti,omap34xx-temperature-sensor" for OMAP34xx
> > +	- "ti,omap36xx-temperature-sensor" for OMAP36xx
> > +- syscon :	Should be a phandle to system configuration node which
> > +		encompases the temperature register
> > +- clocks :	Should contain 32KHz fclk clock specifier
> > +- clock-names :	Should contain clock names
> > +	- "fck" for the 32KHz fclk clock specifier
> 
> I don't quite get it. The temperature sensor is internal on the CPU,
> right? Why do we need device tree to describe it? As soon as we have
> CPU that is compatible to ti,omap3430, we know everything we need to
> know, no?

Lots of stuff is SoC internal and described in the DT (e.g. serial
controllers). Just have a look in omap3.dtsi or omap34xx.dtsi.

I put the temperature sensor into its own node for the following
reasons:

 * syscon reference
 * clock reference

I first thought about loading the driver from the syscon driver,
but omap uses a generic one, so that's not an option. Apart from
that one would still need the clock reference.

> > +Example for omap34xx:
> > +
> > +/ {
> > +	temperature-sensor {
> > +		compatible = "ti,omap34xx-temperature-sensor";
> > +		syscon = <&omap3_scm_general>;
> > +		clocks = <&ts_fck>;
> > +		clock-names = "fck";
> > +	};
> > +};
> 
> Or is there something that depends on the board there? Or do we want
> to do it like this to be consistent with existing bindings?

This is SoC specific and should go into the omap34xx.dtsi and
omap36xx.dtsi files. See also PATCH 3/3.

-- Sebastian

On Fri 2014-12-26 13:34:52, Sebastian Reichel wrote:
> OMAP34xx and OMAP36xx processors contain a register in the syscon area,
> which can be used to determine the SoCs temperature. This provides a
> DT binding specification for the temperature monitor.
> 
> Signed-off-by: Sebastian Reichel <sre@kernel.org>

Acked-by: Pavel Machek <pavel@ucw.cz>
								Pavel