linux-kernel - Re: [PATCH] thermal: of: Introduce governor selection in dts

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Date:	Mon, 10 Aug 2015 18:47:23 +0100
From:	Javi Merino <javi.merino@....com>
To:	Chung-Yih Wang (王崇懿) <cywang@...gle.com>,
	Zhang Rui <rui.zhang@...el.com>,
	Eduardo Valentin <edubezval@...il.com>
Cc:	Mark Rutland <Mark.Rutland@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <Pawel.Moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH] thermal: of: Introduce governor selection in dts

On Mon, Aug 10, 2015 at 09:00:49AM +0100, Chung-Yih Wang (王崇懿) wrote:
> This patch was originally introduced when we made power_allocator the
> default governor where we had issues in binding a thermal zone w/o
> parameters to. Then we came out this facility for binding a specific
> governor to a thermal zone in dts instead of the default governor.
> Javi seems like this idea much.

While I can understand why this is not suitable for devicetree, we
should have a way in the kernel to configure different governors for
different thermal zones defined in device tree.  Thermal zones defined
from platform code can choose the thermal governor when they are
registered.

If this information can't go in device tree, where can we put it? As
an additional parameter to thermal_zone_of_sensor_register()?

Cheers,
Javi

> On Fri, Aug 7, 2015 at 6:31 PM, Mark Rutland <mark.rutland@....com> wrote:
> > On Fri, Aug 07, 2015 at 08:09:39AM +0100, Chung-Yih Wang (王崇懿) wrote:
> >> As there could be more thermal zones on a system and
> >> more variety in thermal governors provided in kernel,
> >> this patch provides flexibility of governor selection
> >> for a thermal zone declared in device tree.
> >>
> >> Change-Id: Ie4a75d762709cbbe9f1806dae325d13f71982e78
> >> Signed-off-by: Chung-yih Wang <cywang@...omium.org>
> >> ---
> >>  Documentation/devicetree/bindings/thermal/thermal.txt |  9 +++++++++
> >>  drivers/thermal/of-thermal.c                          | 10 ++++++++++
> >>  2 files changed, 19 insertions(+)
> >>
> >> diff --git a/Documentation/devicetree/bindings/thermal/thermal.txt
> >> b/Documentation/devicetree/bindings/thermal/thermal.txt
> >> index 8a49362..30a5d41 100644
> >> --- a/Documentation/devicetree/bindings/thermal/thermal.txt
> >> +++ b/Documentation/devicetree/bindings/thermal/thermal.txt
> >> @@ -174,6 +174,13 @@ Optional property:
> >>                         2000mW, while on a 10'' tablet is around
> >>                         4500mW.
> >>
> >> +- thermal-governor-name:       The name of governor used to control the
> >> +                               thermal zone instead of the default one
> >> +                               specified in kernel config. For reference, if
> >> +                               default governor is step_wise, one could
> >> +                               select power_allocator for cpu_thermal zone
> >> +                               in dts.
> >
> >
> > This is not a hardware or system property, but rather a Linux
> > implementation detail.
> >
> > This really shouldn't go in the DT.
> >
> > Mark.
> >
> >> +
> >>  Note: The delay properties are bound to the maximum dT/dt (temperature
> >>  derivative over time) in two situations for a thermal zone:
> >>  (i)  - when passive cooling is activated (polling-delay-passive); and
> >> @@ -555,6 +562,8 @@ thermal-zones {
> >>
> >>                 sustainable-power = <2500>;
> >>
> >> +               thermal-governor-name = "power_allocator";
> >> +
> >>                 trips {
> >>                         /* Trips are based on resulting linear equation */
> >>                         cpu_trip: cpu-trip {
> >> diff --git a/drivers/thermal/of-thermal.c b/drivers/thermal/of-thermal.c
> >> index b295b2b..45570ac 100644
> >> --- a/drivers/thermal/of-thermal.c
> >> +++ b/drivers/thermal/of-thermal.c
> >> @@ -882,6 +882,7 @@ int __init of_parse_thermal_zones(void)
> >>         }
> >>
> >>         for_each_child_of_node(np, child) {
> >> +               const char *governor_name;
> >>                 struct thermal_zone_device *zone;
> >>                 struct thermal_zone_params *tzp;
> >>                 int i, mask = 0;
> >> @@ -909,6 +910,15 @@ int __init of_parse_thermal_zones(void)
> >>                         goto exit_free;
> >>                 }
> >>
> >> +               /* Select a preferred governor if declared */
> >> +               if (!of_property_read_string(child,
> >> +                                            "thermal-governor-name",
> >> +                                            &governor_name)) {
> >> +                       strncpy(tzp->governor_name,
> >> +                               governor_name,
> >> +                               sizeof(tzp->governor_name) - 1);
> >> +               }
> >> +
> >>                 /* No hwmon because there might be hwmon drivers registering */
> >>                 tzp->no_hwmon = true;
> >>
> >> --
> >> 2.1.2
> >>
> 
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