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

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Date:   Fri, 13 Sep 2019 11:42:41 -0500
From:   Adam Ford <aford173@...il.com>
To:     "H. Nikolaus Schaller" <hns@...delico.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

On Fri, Sep 13, 2019 at 11:35 AM Adam Ford <aford173@...il.com> wrote:
>
> On Fri, Sep 13, 2019 at 10:09 AM H. Nikolaus Schaller <hns@...delico.com> wrote:
> >
> >
> > > 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.
>
> 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

adam
>
> >
> > >
> > > adam
> >
> > BR and thanks,
> > Nikolaus
> >