Re: [PATCH v5 15/15] devicetree: bindings: Document qcom,pvs

[Rob Herring]

On Wed, Dec 27, 2017 at 4:20 AM, Sricharan R <sricharan@xxxxxxxxxxxxxx> wrote:
> Hi Rob,
>
> On 12/26/2017 11:06 PM, Rob Herring wrote:
>> On Thu, Dec 21, 2017 at 5:53 AM, Sricharan R <sricharan@xxxxxxxxxxxxxx> wrote:
>>> Hi Rob,
>>>
>>> On 12/21/2017 2:48 AM, Rob Herring wrote:
>>>> On Wed, Dec 20, 2017 at 11:55:33AM +0530, Sricharan R wrote:
>>>>> Hi Viresh,
>>>>>
>>>>> On 12/20/2017 8:56 AM, Viresh Kumar wrote:
>>>>>> On 19-12-17, 21:25, Sricharan R wrote:
>>>>>>> +  cpu@0 {
>>>>>>> +          compatible = "qcom,krait";
>>>>>>> +          enable-method = "qcom,kpss-acc-v1";
>>>>>>> +          device_type = "cpu";
>>>>>>> +          reg = <0>;
>>>>>>> +          qcom,acc = <&acc0>;
>>>>>>> +          qcom,saw = <&saw0>;
>>>>>>> +          clocks = <&kraitcc 0>;
>>>>>>> +          clock-names = "cpu";
>>>>>>> +          cpu-supply = <&smb208_s2a>;
>>>>>>> +          operating-points-v2 = <&cpu_opp_table>;
>>>>>>> +  };
>>>>>>> +
>>>>>>> +  qcom,pvs {
>>>>>>> +          qcom,pvs-format-a;
>>>>>>> +  };
>>>>>>
>>>>>> Not sure what Rob is going to say on that :)
>>>>>>
>>>>>
>>>>>  Yes. Would be good to know the best way.
>>>>
>>>> Seems like this should be a property of an efuse node either implied by
>>>> the compatible or a separate property. What determines format A vs. B?
>>>>
>>>
>>>  Yes, this efuse registers are part of the eeprom (qfprom) tied to the soc.
>>>  So this property (details like bitfields and register offsets that it represents)
>>>  can be put soc specific and nvmem apis can be used to read
>>>  the registers. Does something like below look ok ?
>>>
>>>  qcom,pvs {
>>>         compatible = "qcom,pvs-ipq8064";
>>>         nvmem-cells = <&pvs_efuse>;
>>>  }
>>
>> Why do you need this node? It doesn't look like it corresponds to a
>> h/w block. It looks like you are just creating it to instantiate a
>> driver.
>>
>>>  qfprom: qfprom@700000 {
>>>         compatible      = "qcom,qfprom";
>>
>> Either this or...
>>
>>>         reg             = <0x00700000 0x1000>;
>>>         #address-cells  = <1>;
>>>         #size-cells     = <1>;
>>>         ranges;
>>>         pvs_efuse: pvs {
>>
>> a compatible here should be specific enough so the OS can know what
>> the bits are.
>
>  Infact the above "qcom,pvs" node is required mainly to act as a consumer
>  for the nvmem data provider ("qcom,qfprom") (using nvmem-cells = <&pvs_efuse>)
>  Then "qfprom" can be made to contain a "format_a" or "format_b" specific cell.
>
>  So all that is needed is, nvmem-cells = <&pvs_efuse_phandle> needs to be available
>  somewhere. The requirement is similar what is now done by "operating-points-v2-ti-cpu"
>  and the ti-cpufreq.c. There "operating-points-v2-ti-cpu" node, contains the syscon
>  register to read the efuse values. Similarly does defining a new
>  "operating-points-v2-krait-cpu" which would contain the nvmem-cells property look ok ?
>  This would avoid defining a new qcom,pvs node.

Yes, this seems reasonable.

>
>         cpu@0 {
>                 compatible = "qcom,krait";
>                 enable-method = "qcom,kpss-acc-v1";
>                 device_type = "cpu";
>                 reg = <0>;
>                 qcom,acc = <&acc0>;
>                 qcom,saw = <&saw0>;
>                 clocks = <&kraitcc 0>;
>                 clock-names = "cpu";
>                 cpu-supply = <&smb208_s2a>;
>                 operating-points-v2 = <&cpu_opp_table>;
>         };
>
>         cpu_opp_table: opp_table {
>                 compatible = "operating-points-v2-krait-cpu";
>
>                 nvmem-cells = <&pvs_efuse_format_a>;
>                 /*
>                  * Missing opp-shared property means CPUs switch DVFS states
>                  * independently.
>                  */
>
>                 opp-1400000000 {
>                         opp-hz = /bits/ 64 <1400000000>;
>                         opp-microvolt-speed0-pvs0-v0 = <1250000>;
>                         opp-microvolt-speed0-pvs1-v0 = <1175000>;
>                         opp-microvolt-speed0-pvs2-v0 = <1125000>;
>                         opp-microvolt-speed0-pvs3-v0 = <1050000>;
>
>                 };
>                 ...
>         }
>
>         qfprom: qfprom@700000 {
>                 compatible      = "qcom,qfprom";
>                 reg             = <0x00700000 0x1000>;
>                 #address-cells  = <1>;
>                 #size-cells     = <1>;
>                 ranges;
>                 pvs_efuse_format_a: pvs {
>                         reg = <0xc0 0x8>;
>                 };
>         }
>
> Regards,
>  Sricharan
>
> --
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