Is cpufreq-dt safe without regulator support?

[Nishanth Menon]

On Tue, Mar 17, 2015 at 1:22 PM, Lucas Stach <l.stach at pengutronix.de> wrote:
> Am Dienstag, den 17.03.2015, 15:45 +0800 schrieb wens Tsai:
>> Hi Viresh,
>>
>> The sunxi platform added cpufreq support in 4.0.0-rc1 using
>> the generic cpufreq-dt driver. One issue we've run into is
>> the default OPPs we use include an overclocked/overvoltage
>> setting.
>>
>> If the cpu is missing a regulator supply phandle, or the
>> kernel is built without regulators, cpufreq can increase
>> the clock rate without the needed voltage increase.
>>
>> The former issue can be resolved by providing a dummy
>> regulator with the default voltage, effectively disabling
>> cpufreq.
>>
>> The latter is possible. Without regulator support built-in,
>> even a correct, complete DTS can still fail. Should I just
>> remove the offending OPP? Still that does not fix the
>> problem when we actually do want overclocking.
>>
>> To summarize, should cpufreq-dt probe fail when regulator
>> support isn't available? Should we differentiate between
>> not having a regulator phandle vs no regulator support?
>>
> If you have an OPP in the DTS that is not stable with the boot voltage
> then you need to handle this case in you platform code by disabling this
> OPP if no regulator support is built into the kernel.
>
> You can look at the i.MX code to see how this can be done. It is used
> there to disable an OPP depending on fuse settings.


Something we want to do generically?

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Regards,
Nishanth Menon