linux-kernel - Re: [PATCH v3 4/4] thermal: cpuidle: Register cpuidle cooling device

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Message-ID: <db4eeecf-2126-e455-ef02-fc034c631e09@arm.com>
Date:   Tue, 28 Apr 2020 16:31:40 +0100
From:   Lukasz Luba <lukasz.luba@....com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>, rui.zhang@...el.com
Cc:     amit.kucheria@...durent.com,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        "open list:CPU IDLE TIME MANAGEMENT FRAMEWORK" 
        <linux-pm@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:CPUIDLE DRIVER - ARM PSCI" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3 4/4] thermal: cpuidle: Register cpuidle cooling device



On 4/14/20 11:08 PM, 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/cpuidle-arm.c  | 5 +++++
>   drivers/cpuidle/cpuidle-psci.c | 5 +++++
>   2 files changed, 10 insertions(+)
> 
> diff --git a/drivers/cpuidle/cpuidle-arm.c b/drivers/cpuidle/cpuidle-arm.c
> index 9e5156d39627..2406ac0ae134 100644
> --- a/drivers/cpuidle/cpuidle-arm.c
> +++ b/drivers/cpuidle/cpuidle-arm.c
> @@ -8,6 +8,7 @@
>   
>   #define pr_fmt(fmt) "CPUidle arm: " fmt
>   
> +#include <linux/cpu_cooling.h>
>   #include <linux/cpuidle.h>
>   #include <linux/cpumask.h>
>   #include <linux/cpu_pm.h>
> @@ -124,6 +125,10 @@ static int __init arm_idle_init_cpu(int cpu)
>   	if (ret)
>   		goto out_kfree_drv;
>   
> +	ret = cpuidle_cooling_register(drv);
> +	if (ret)
> +		pr_err("Failed to register the idle cooling device: %d\n", ret);

This and similar from cpuidle-psci.c might produce a lot of error log
entries. The 'return 0' below does not take into account that we failed
to register cpuidle cooling. Thus, I would rather ignore the return from 
cpuidle_cooling_register and move this print into
cpuidle_cooling_register function, changing it also to debug level.

> +
>   	return 0;
>   
>   out_kfree_drv:
> diff --git a/drivers/cpuidle/cpuidle-psci.c b/drivers/cpuidle/cpuidle-psci.c
> index edd7a54ef0d3..8e805bff646f 100644
> --- a/drivers/cpuidle/cpuidle-psci.c
> +++ b/drivers/cpuidle/cpuidle-psci.c
> @@ -9,6 +9,7 @@
>   #define pr_fmt(fmt) "CPUidle PSCI: " fmt
>   
>   #include <linux/cpuhotplug.h>
> +#include <linux/cpu_cooling.h>
>   #include <linux/cpuidle.h>
>   #include <linux/cpumask.h>
>   #include <linux/cpu_pm.h>
> @@ -305,6 +306,10 @@ static int __init psci_idle_init_cpu(int cpu)
>   	if (ret)
>   		goto out_kfree_drv;
>   
> +	ret = cpuidle_cooling_register(drv);
> +	if (ret)
> +		pr_err("Failed to register the idle cooling device: %d\n", ret);
> +

The same here. I would change it into one line:
+	cpuidle_cooling_register(drv);

>   	return 0;
>   
>   out_kfree_drv:
> 

Regards,
Lukasz