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

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Date:	Mon, 10 Aug 2015 16:00:49 +0800
From:	Chung-Yih Wang (王崇懿) 
	<cywang@...gle.com>
To:	Mark Rutland <mark.rutland@....com>, javi.merino@....com
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Zhang Rui <rui.zhang@...el.com>,
	Eduardo Valentin <edubezval@...il.com>,
	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

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.

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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