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

Dave Gerlach
2016-11-02T16:03:13Z

Hi,
On 11/01/2016 10:59 PM, Viresh Kumar wrote:
> 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@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.
>

Does that still apply when opp-supported-hw is involved? Based on the
comment at the start of the table, those OPPs are all mutually exclusive
and will not ever be enabled on the same piece of silicon, they
represent the lowest OPP for each of three different supported-hw
configurations.

Regards,
Dave