On 07/11/2012 07:56 AM, Prashant Gaikwad wrote:
> Hi,
>
> I am working on DT binding for Tegra DVFS.
>
> For Tegra, DVFS node mainly consists of frequency and voltage pairs.
> Frequency in the pair may change for different process. E.g. for process
> 1 CPU clock frequency could be 900MHz at 1V while for process 2 it could
> be 1GHz at 1V.
> Tegra uses vendor specific ids to identify the correct frequency table.
>
> Following is the proposed binding for voltage and frequency tables used
> in DVFS. Looking for comments/suggestions to make it generic.
>
> =======DVFS table node===================
> This node defines the voltage configuration for the DVFS which includes
> the regulator and voltage array.
>
> Required properties:
>
> reg_id : <regulator phandle>;
> voltage-table : <voltage array, values in mV>;
>
> #address-cells and #size-cells : To identify correct frequency table
> using process id (or some other vendor specific way).
>
> ========Frequency table node===============
>
> This node defines frequency configuration for the device DVFS.
>
> Required properties:
>
> In device node need a reference to the DVFS table node.
>
> dvfs : the phandle for the DVFS table node
>
> frequency-table@n
> reg = <n>; dependent on address-cells and size-cells in DVFS
> table node.
> frequencies = <frequency array, values in MHz>;
You are storing u32 values, why limit the resolution to MHz.
Put the unit in the property names.
> }
>
> Example:
> -------------------------------------------------------------------------
>
> cpu-dvfs-table : dvfs-table {
This should be located with the node that the frequencies correspond to.
> compatible = "nvidia,tegra30-dvfs-table";
> reg_id = <&sm0>;
> #address-cells = <1>;
> #size-cells = <0>;
> voltage-array = <750 775 800 825 850 875 900 925 950 975
> 1000 1025 1050 1100 1125>;
The SOC is really characterized at all these voltages?
> };
>
> device {
> dvfs = <&cpu-dvfs-table>;
> frequency-table@102 {
> reg = <0x102>;
> frequencies = <314 314 314 456 456 456 608 608 608
> 760 817 817 912 1000>;
I don't see the point of repeating frequencies.
> };
> frequency-table@002 {
> reg = <0x002>;
> frequencies = <598 598 750 750 893 893 1000>;
> };
How do you determine the voltage for a frequency on table 2?
I'd expect a single property with freq/volt pairs or 2 properties for
freq and voltage where there is a 1:1 relationship (freq N uses voltage N).
Rob
> };
>
> Thanks & Regards,
> Prashant G
>
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