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

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Date:   Thu, 19 Dec 2019 14:51:03 -0800
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Daniel Lezcano <daniel.lezcano@...aro.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

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.

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