[PATCH v3 2/3] Documentation: dt: add bindings for ti-cpufreq

[Viresh Kumar]

On 27-10-16, 16:41, Dave Gerlach wrote:
> Add the device tree bindings document for the TI CPUFreq/OPP driver
> on AM33xx and AM43xx SoCs. The operating-points-v2 binding allows us
> to provide an opp-supported-hw property for each OPP to define when
> it is available. This driver is responsible for reading and parsing
> registers to determine which OPPs can be selectively enabled based
> on the specific SoC in use by matching against the opp-supported-hw
> data.
> 
> Signed-off-by: Dave Gerlach <d-gerlach at ti.com>
> ---
> v2->v3:
> - Move ti,syscon-* properties under opp table instead of cpu node, as
>   that is a better location for them.
> - For the opp table do not use platform specific compatible strings
>   but instead a operating-points-v2-ti-cpu
> 
>  .../devicetree/bindings/cpufreq/ti-cpufreq.txt     | 132 +++++++++++++++++++++
>  1 file changed, 132 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/cpufreq/ti-cpufreq.txt
> 
> diff --git a/Documentation/devicetree/bindings/cpufreq/ti-cpufreq.txt b/Documentation/devicetree/bindings/cpufreq/ti-cpufreq.txt
> new file mode 100644
> index 000000000000..467ad29c75c9
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/cpufreq/ti-cpufreq.txt
> @@ -0,0 +1,132 @@
> +TI CPUFreq and OPP bindings
> +================================
> +
> +Certain TI SoCs, like those in the am335x, am437x, am57xx, and dra7xx
> +families support different OPPs depending on the silicon variant in use.
> +The ti_cpufreq driver can use revision and an efuse value from the SoC to
> +provide the OPP framework with supported hardware information. This is
> +used to determine which OPPs from the operating-points-v2 table get enabled
> +when it is parsed by the OPP framework.
> +
> +Required properties:
> +--------------------
> +In 'cpus' nodes:
> +- operating-points-v2: Phandle to the operating-points-v2 table to use.
> +
> +In 'operating-points-v2' table:
> +- compatible: Should be 'operating-points-v2-ti-cpu' for am335x, am43xx,
> +	      and dra7xx/am57xx SoCs
> +- ti,syscon-efuse: Syscon phandle, offset to efuse register, efuse register
> +		   mask, and efuse register shift to get the relevant bits
> +		   that describe OPP availability.
> +- ti,syscon-rev: Syscon and offset used to look up revision value on SoC.
> +
> +Optional properties:
> +--------------------
> +For each opp entry in 'operating-points-v2' table:
> +- opp-supported-hw: Two bitfields indicating:
> +	1. Which revision of the SoC the OPP is supported by
> +	2. Which eFuse bits indicate this OPP is available
> +
> +	A bitwise AND is performed against these values and if any bit
> +	matches, the OPP gets enabled. Not providing the property for an
> +	entry indicates that an OPP is always supported.
> +
> +Example:
> +--------
> +
> +/* From arch/arm/boot/dts/am33xx.dtsi */
> +cpus {
> +	#address-cells = <1>;
> +	#size-cells = <0>;
> +	cpu at 0 {
> +		compatible = "arm,cortex-a8";
> +		device_type = "cpu";
> +		reg = <0>;
> +
> +		operating-points-v2 = <&cpu0_opp_table>;
> +
> +		clocks = <&dpll_mpu_ck>;
> +		clock-names = "cpu";
> +
> +		clock-latency = <300000>; /* From omap-cpufreq driver */
> +	};
> +};
> +
> +/*
> + * cpu0 has different OPPs depending on SoC revision and some on revisions
> + * 0x2 and 0x4 have eFuse bits that indicate if they are available or not
> + */
> +cpu0_opp_table: opp_table0 {
> +	compatible = "operating-points-v2-ti-am3352-cpu";
> +	ti,syscon-efuse = <&scm_conf 0x7fc 0x1fff 0>;
> +	ti,syscon-rev = <&scm_conf 0x600>;
> +
> +	/*
> +	 * The three following nodes are marked with opp-suspend
> +	 * because they can not be enabled simultaneously on a
> +	 * single SoC.
> +	 */
> +	opp50 at 300000000 {
> +		opp-hz = /bits/ 64 <300000000>;
> +		opp-microvolt = <950000 931000 969000>;
> +		opp-supported-hw = <0x06 0x0010>;
> +		opp-suspend;
> +	};
> +
> +	opp100 at 275000000 {
> +		opp-hz = /bits/ 64 <275000000>;
> +		opp-microvolt = <1100000 1078000 1122000>;
> +		opp-supported-hw = <0x01 0x00FF>;
> +		opp-suspend;
> +	};
> +
> +	opp100 at 300000000 {
> +		opp-hz = /bits/ 64 <300000000>;
> +		opp-microvolt = <1100000 1078000 1122000>;
> +		opp-supported-hw = <0x06 0x0020>;
> +		opp-suspend;

Only one OPP in the table can be marked as suspend OPP.

-- 
viresh