On 07/11/2012 11:08 PM, Prashant Gaikwad wrote:
> On Wednesday 11 July 2012 07:33 PM, Rob Herring wrote:
>> On 07/11/2012 07:56 AM, Prashant Gaikwad wrote:
>>> 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.
>
>>> 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.
>
>>> };
>>>
>>> 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).
>
>
> 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>;
Rob
>
> 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.
>
>> Rob
>>
>>> };
>>>
>>> Thanks& Regards,
>>> Prashant G
>>>
>>> _______________________________________________
>>> linux-arm-kernel mailing list
>>> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
>>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>>
>
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