linux-kernel - Re: [RFC PATCH 1/2] cpuidle: Add idle enter/exit time stamp for notifying current idle state.

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Date:	Tue, 02 Apr 2013 07:00:11 +0200
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	Jonghwa Lee <jonghwa3.lee@...sung.com>
CC:	"Rafael J. Wysocki" <rjw@...k.pl>, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org, cpufreq@...r.kernel.org,
	MyungJoo Ham <myungjoo.ham@...sung.com>,
	Lukasz Majewski <l.majewski@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Chanwoo Choi <cw00.choi@...sung.com>, sw0312.kim@...sung.com,
	m.szyprowski@...sung.com
Subject: Re: [RFC PATCH 1/2] cpuidle: Add idle enter/exit time stamp for notifying
 current idle state.

On 04/01/2013 10:24 AM, Jonghwa Lee wrote:
> This patch adds idle state time stamp to cpuidle device structure to
> notify its current idle state. If last enter time is newer than last
> exit time, then it means that the core is in idle now.
> 
> Signed-off-by: Jonghwa Lee <jonghwa3.lee@...sung.com>
> ---

The patch description does not explain what problem you want to solve,
how to solve it and the patch itself shows nothing.

Could you elaborate ?

Thanks
  -- Daniel

>  drivers/cpuidle/cpuidle.c |    8 ++++----
>  include/linux/cpuidle.h   |    4 ++++
>  2 files changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
> index eba6929..1e830cc 100644
> --- a/drivers/cpuidle/cpuidle.c
> +++ b/drivers/cpuidle/cpuidle.c
> @@ -233,18 +233,18 @@ int cpuidle_wrap_enter(struct cpuidle_device *dev,
>  				int (*enter)(struct cpuidle_device *dev,
>  					struct cpuidle_driver *drv, int index))
>  {
> -	ktime_t time_start, time_end;
>  	s64 diff;
>  
> -	time_start = ktime_get();
> +	dev->last_idle_start = ktime_get();
>  
>  	index = enter(dev, drv, index);
>  
> -	time_end = ktime_get();
> +	dev->last_idle_end = ktime_get();
>  
>  	local_irq_enable();
>  
> -	diff = ktime_to_us(ktime_sub(time_end, time_start));
> +	diff = ktime_to_us(ktime_sub(dev->last_idle_end,
> +				dev->last_idle_start));
>  	if (diff > INT_MAX)
>  		diff = INT_MAX;
>  
> diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
> index 480c14d..d1af05f 100644
> --- a/include/linux/cpuidle.h
> +++ b/include/linux/cpuidle.h
> @@ -16,6 +16,7 @@
>  #include <linux/kobject.h>
>  #include <linux/completion.h>
>  #include <linux/hrtimer.h>
> +#include <linux/ktime.h>
>  
>  #define CPUIDLE_STATE_MAX	8
>  #define CPUIDLE_NAME_LEN	16
> @@ -74,6 +75,9 @@ struct cpuidle_device {
>  	struct kobject		kobj;
>  	struct completion	kobj_unregister;
>  
> +	ktime_t			last_idle_start;
> +	ktime_t			last_idle_end;
> +
>  #ifdef CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED
>  	int			safe_state_index;
>  	cpumask_t		coupled_cpus;
> 


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