linux-kernel - Re: [PATCH 2/2] thermal: cpuidle: Register cpuidle cooling device

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Message-ID: <c08b76d1-5525-7d0e-7d11-da3584d2adcc@linaro.org>
Date:   Thu, 19 Dec 2019 23:57:04 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        "open list:CPU IDLE TIME MANAGEMENT FRAMEWORK" 
        <linux-pm@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] thermal: cpuidle: Register cpuidle cooling device

On 19/12/2019 23:51, Matthias Kaehlcke wrote:
> Hi Daniel,
> 
> On Thu, Dec 19, 2019 at 11:19:28PM +0100, Daniel Lezcano wrote:
>> The cpuidle driver can be used as a cooling device by injecting idle
>> cycles. The DT binding for the idle state added an optional
>>
>> When the property is set, register the cpuidle driver with the idle
>> state node pointer as a cooling device. The thermal framework will do
>> the association automatically with the thermal zone via the
>> cooling-device defined in the device tree cooling-maps section.
>>
>> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
>> ---
>>  drivers/cpuidle/dt_idle_states.c | 8 ++++++++
>>  1 file changed, 8 insertions(+)
>>
>> diff --git a/drivers/cpuidle/dt_idle_states.c b/drivers/cpuidle/dt_idle_states.c
>> index d06d21a9525d..34bd65197342 100644
>> --- a/drivers/cpuidle/dt_idle_states.c
>> +++ b/drivers/cpuidle/dt_idle_states.c
>> @@ -8,6 +8,7 @@
>>  
>>  #define pr_fmt(fmt) "DT idle-states: " fmt
>>  
>> +#include <linux/cpu_cooling.h>
>>  #include <linux/cpuidle.h>
>>  #include <linux/cpumask.h>
>>  #include <linux/errno.h>
>> @@ -205,6 +206,13 @@ int dt_init_idle_driver(struct cpuidle_driver *drv,
>>  			err = -EINVAL;
>>  			break;
>>  		}
>> +
>> +		if (of_find_property(state_node, "#cooling-cells", NULL)) {
>> +			err = cpuidle_of_cooling_register(state_node, drv);
> 
> cpuidle_of_cooling_register() returns a struct thermal_cooling_device *,
> so you probably want to use PTR_ERR() here.

Right, I'm about the send the V6 which returns an int.

> Could it be a problem that the cooling device isn't unregistered even when all
> associated cores are taken offline?

The cooling device relies on the powercap/idle_inject.c which is based
on the smpboot API. This one takes care of parking the per cpu pinned
tasks. So AFAICS, it is fine.

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