Re: [RFC] ARM: dts: omap36xx: Enable thermal throttling

[Daniel Lezcano]

On 18/09/2019 11:24, Viresh Kumar wrote:
> On 13-09-19, 00:33, Daniel Lezcano wrote:
>>
>> Hi Adam,
>>
>> On 12/09/2019 23:19, Adam Ford wrote:
>>> On Thu, Sep 12, 2019 at 4:12 PM Daniel Lezcano
>>> <daniel.lezcano@xxxxxxxxxx> wrote:
>>>>
>>>> On 12/09/2019 20:30, Adam Ford wrote:
>>>>> The thermal sensor in the omap3 family isn't accurate, but it's
>>>>> better than nothing.  The various OPP's enabled for the omap3630
>>>>> support up to OPP1G, however the datasheet for the DM3730 states
>>>>> that OPP130 and OPP1G are not available above TJ of 90C.
>>>>>
>>>>> This patch configures the thermal throttling to limit the
>>>>> operating points of the omap3630 to Only OPP50 and OPP100 if
>>>>> the thermal sensor reads a value above 90C.
>>
>> Oh, that's a very interesting use case.
>>
>> AFAICT the thermal framework is not designed to deal with this
>> situation. I agree this setup may work (even if I'm not convinced about
>> the stability of the whole).
>>
>> May be Viresh can help for the cpufreq side?
> 
> Sorry but I am not able to understand what's not supported by thermal framework
> here and what can I do to help :)

The solution of preventing running above the 90ÂC by changing the OPPs
is fine and works. It is a way of workaround the spec.

But AFAIU, the specs of the board say the OPPs 800MHz and 1GHz are only
permitted during an amount of time above 90ÂC which makes the constraint
inverted and recall somehow the 'turbo-mode' description:

"
- turbo-mode: Marks the OPP to be used only for turbo modes. Turbo mode
is available on some platforms, where the device can run over its
operating frequency for a short duration of time limited by the device's
power, current and thermal limits.
"

This is where I thought you can give an input.


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