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SubjectRe: [RFC] ARM: dts: omap36xx: Enable thermal throttling
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> Am 13.09.2019 um 18:42 schrieb Adam Ford <aford173@gmail.com>:
>
> On Fri, Sep 13, 2019 at 11:35 AM Adam Ford <aford173@gmail.com> wrote:
>>
>> On Fri, Sep 13, 2019 at 10:09 AM H. Nikolaus Schaller <hns@goldelico.com> wrote:
>>>
>>>
>>>> Am 13.09.2019 um 17:01 schrieb Adam Ford <aford173@gmail.com>:
>>>>
>>>> On Fri, Sep 13, 2019 at 9:24 AM H. Nikolaus Schaller <hns@goldelico.com> wrote:
>>>>>
>>>>>
>>>>>> Am 13.09.2019 um 16:05 schrieb Adam Ford <aford173@gmail.com>:
>>>>>>
>>>>>> On Fri, Sep 13, 2019 at 8:32 AM H. Nikolaus Schaller <hns@goldelico.com> wrote:
>>>>>>>
>>>>>>> Hi Adam,
>>>>>>>
>>>>>>>> Am 13.09.2019 um 13:07 schrieb Adam Ford <aford173@gmail.com>:
>>>>>>>
>>>>>>>>>> + cpu_cooling_maps: cooling-maps {
>>>>>>>>>> + map0 {
>>>>>>>>>> + trip = <&cpu_alert0>;
>>>>>>>>>> + /* Only allow OPP50 and OPP100 */
>>>>>>>>>> + cooling-device = <&cpu 0 1>;
>>>>>>>>>
>>>>>>>>> omap4-cpu-thermal.dtsi uses THERMAL_NO_LIMIT constants but I do not
>>>>>>>>> understand their meaning (and how it relates to the opp list).
>>>>>>>>
>>>>>>>> I read through the documentation, but it wasn't completely clear to
>>>>>>>> me. AFAICT, the numbers after &cpu represent the min and max index in
>>>>>>>> the OPP table when the condition is hit.
>>>>>>>
>>>>>>> Ok. It seems to use "cooling state" for those and the first is minimum
>>>>>>> and the last is maximum. Using THERMAL_NO_LIMIT (-1UL) means to have
>>>>>>> no limits.
>>>>>>>
>>>>>>> Since here we use the &cpu node it is likely that the "cooling state"
>>>>>>> is the same as the OPP index currently in use.
>>>>>>>
>>>>>>> I have looked through the .dts which use cpu_crit and the picture is
>>>>>>> not unique...
>>>>>>>
>>>>>>> omap4 seems to only define it
>>>>>>> am57xx has two different grade dtsi files
>>>>>>> dra7 overwrites critical temperature value
>>>>>>> am57xx-beagle defines a gpio to control a fan
>>>>>>
>>>>
>>>> I am going to push a separate but related RFC with 2 patches in the
>>>> series. This new one will setup the alerts and maps without any
>>>> throttling for all omap3's in the first patch. The second patch will
>>>> consolidate the thermal references to omap3.dtsi so omap34, omap36 and
>>>> am35 can all use them without having to duplicate the entries.
>>>>
>>>> It will make the omap36xx changes simpler to manage, because we can
>>>> just modify a portion of the entries instead of having the whole
>>>> table.
>>>>
>>>> Once this parallel RFC gets comments/feedback, I'll re-integrate the
>>>> omap36xx throttling.
>>>
>>> Good idea. I have looked over them and they seem to be ok.
>>
>> Rebasing my omap36xx throttling after the v2 RFC I pushed moving the
>> omap3-cpu thermal stuff, I modified the omap36xx accordingly to try
>> and force the alert condition:
>>
>> &cpu_alert0 {
>> temperature = <55000>; /* millicelsius */
>> };
>>
>> &cpu_cooling_maps {
>> map0 {
>> /* OPP130 and OPP1G are not available above 90C */
>> cooling-device = <&cpu 0 2>;
>> };
>> };
>>
>> I would expect that with the temperature set for 55C, it would have
>> done something, but it doesn't appear to be working as I would expect.
>>
>> # cat /sys/devices/virtual/thermal/thermal_zone0/temp
>> 58500
>>
>> # cat /sys/devices/system/cpu/cpufreq/policy0/scaling_available_frequencies
>> 300000 600000 800000
>> #
>>
>> :-(
>>
>
> Good news (I think)
>
> With cooling-device = <&cpu 1 2> setup, I was able to ask the max
> frequency and it returned 600MHz.
>
> # cat /sys/devices/virtual/thermal/thermal_zone0/temp
> 58500
> # cat /sys/devices/system/cpu/cpufreq/policy0/scaling_available_frequencies
> 300000 600000 800000
> # cat /sys/devices/system/cpu/cpufreq/policy0/scaling_m
> scaling_max_freq scaling_min_freq
> # cat /sys/devices/system/cpu/cpufreq/policy0/scaling_max_freq
> 600000

looks good!
But we have to understand what the <&cpu 1 2> exactly means...

Hopefully someone reading your RFCv2 can answer...

What happens with trip point 60000?
(unfortunately one has to reboot in between or can you kexec between two kernel/dtb versions?)

BR,
Nikolaus

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