On Tuesday 17 July 2012 12:06 AM, Turquette, Mike wrote:

On Sun, Jul 15, 2012 at 4:42 PM, Rob Herring[off-list ref]  wrote:

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On 07/11/2012 11:08 PM, Prashant Gaikwad wrote:

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On Wednesday 11 July 2012 07:33 PM, Rob Herring wrote:

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On 07/11/2012 07:56 AM, Prashant Gaikwad wrote:

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cpu-dvfs-table : dvfs-table {

This should be located with the node that the frequencies correspond to.

With CAR node?

With the power domain it corresponds to or the cpu nodes.

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                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?

Not really, but different processes of single SoC are characterized for
different voltages and this array covers all those voltages.

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};

device {
               dvfs =<&cpu-dvfs-table>;
               frequency-table at 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.

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               };
               frequency-table at 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).

How this will work:

voltage-array =<750 775 800 825 850 875 900  925 950 975 1000 1025 1050
1100 1125>
frequencies-1 =<314 314 314 456 456 456 608  608 608 760 817  817  912
1000>;
frequencies-2 =<598 598 750 750 893 893 1000>;

I don't see the point trying to share a voltage range. Not sharing it is
fewer array elements (22 vs 36):

voltage-array-1 =<750 825 900 975 1000 1050 1100>;
frequencies-1   =<314 456 608 760  817  912 1000>;

voltage-array-2 =<750 800 850  900>
frequencies-2   =<598 750 893 1000>;

This is significantly more readable.

Instead of voltage array, I was thinking of following approach to 
represent operating points for DVFS

reg : operating voltage in microvolt
tolerance : can be used to calculate required voltage. (optional, can be 
replaced by other relevant parameter to calculate required voltage)
frequencies : Array of phandle, clock specifier and frequency for all 
the clocks related to this rail.

opp at 750000000 {
     reg = <750000000>;
     tolerance = <4>;
     frequency-table at 102 {
            reg = <0x102>;
            frequencies = <&osc 0 314000>, <&ref 1 500000>;
     };
};

opp at 800000000 {
     reg = <800000000>;
     tolerance = <4>;
     frequency-table at 102 {
            reg = <0x102>;
            frequencies = <&osc 0 456000>, <&ref 1 608000>;
     };
     frequency-table at 002 {
            reg = <0x002>;
            frequencies = <&osc 0 400000>, <&ref 1 560000>;
     };
};

It represents:
         - 1:1 mapping for voltage/frequency pair.
         - Voltage can be represented as range.
         - relationships between clock domain and rail.

Only issue I see is, if there are large number of operating points it 
will increase data in DT.

Any suggestions?

Regards,
Mike

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Rob

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Freq and voltage has 1:1 relationship but as single voltage table is
used for different processes we have more entries in voltage table than
freq table.
Frequency table 1 is mapped till 1100mV while frequency table 2 is
mapped till 900mV only, it maintains 1:1 relationship.

About repeating frequencies, operating voltage for a frequency would be
the highest one mapped in the table.
For example, in frequency table 2 operating voltage for 750MHz would be
825mV while for 893MHz it would be 875mV. Unmapped entries could be
replaced with 0 to make reading better.

Advantage it provides is single voltage table used for multiple
frequency tables, as can be observed from above tables, operating
voltage for 314MHz in freq table 1 is 800mV while there is no frequency
in table 2 at that voltage.

I know this makes reading difficult but it provides flexibility,

I hope it explains the implementation.

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Rob

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};

Thanks&   Regards,
Prashant G

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