linux-kernel - Re: [RFC] ARM: dts: omap36xx: Enable thermal throttling

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Message-Id: <7C9393BD-B23B-41A6-BF96-E53CD707AAC7@goldelico.com>
Date:   Fri, 13 Sep 2019 17:09:00 +0200
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Adam Ford <aford173@...il.com>
Cc:     Linux-OMAP <linux-omap@...r.kernel.org>,
        Tony Lindgren <tony@...mide.com>,
        André Roth <neolynx@...il.com>,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andreas Kemnade <andreas@...nade.info>,
        Nishanth Menon <nm@...com>, Adam Ford <adam.ford@...icpd.com>,
        kernel@...a-handheld.com
Subject: Re: [RFC] ARM: dts: omap36xx: Enable thermal throttling


> Am 13.09.2019 um 17:01 schrieb Adam Ford <aford173@...il.com>:
> 
> On Fri, Sep 13, 2019 at 9:24 AM H. Nikolaus Schaller <hns@...delico.com> wrote:
>> 
>> 
>>> Am 13.09.2019 um 16:05 schrieb Adam Ford <aford173@...il.com>:
>>> 
>>> On Fri, Sep 13, 2019 at 8:32 AM H. Nikolaus Schaller <hns@...delico.com> wrote:
>>>> 
>>>> Hi Adam,
>>>> 
>>>>> Am 13.09.2019 um 13:07 schrieb Adam Ford <aford173@...il.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.

> 
> adam

BR and thanks,
Nikolaus