linux-kernel - Re: [PATCH 2/3] intel_idle: Removing the redundant calculating for dev->state

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Date:	Sat, 09 Mar 2013 04:00:16 +0100
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	Chuansheng Liu <chuansheng.liu@...el.com>
CC:	lenb@...nel.org, len.brown@...el.com, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] intel_idle: Removing the redundant calculating for
 dev->state_count

On 03/08/2013 04:04 PM, Chuansheng Liu wrote:
> 
> In function intel_idle_cpu_init() and intel_idle_cpuidle_driver_init(),
> they are having the same for(;;) loop.
> 
> Here in intel_idle_cpu_init(), the dev->state_count can be assigned by
> drv->state_count directly.
> 
> Signed-off-by: liu chuansheng <chuansheng.liu@...el.com>
> ---
>  drivers/idle/intel_idle.c |   30 ++----------------------------
>  1 files changed, 2 insertions(+), 28 deletions(-)
> 
> diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
> index 17c9cf9..503b401 100644
> --- a/drivers/idle/intel_idle.c
> +++ b/drivers/idle/intel_idle.c
> @@ -599,38 +599,12 @@ static int intel_idle_cpuidle_driver_init(void)
>   */
>  static int intel_idle_cpu_init(int cpu)
>  {
> -	int cstate;
>  	struct cpuidle_device *dev;
> +	struct cpuidle_driver *drv = &intel_idle_driver;
>  
>  	dev = per_cpu_ptr(intel_idle_cpuidle_devices, cpu);
>  
> -	dev->state_count = 1;
> -
> -	for (cstate = 0; cstate < CPUIDLE_STATE_MAX; ++cstate) {
> -		int num_substates, mwait_hint, mwait_cstate, mwait_substate;
> -
> -		if (cpuidle_state_table[cstate].enter == NULL)
> -			break;
> -
> -		if (cstate + 1 > max_cstate) {
> -			printk(PREFIX "max_cstate %d reached\n", max_cstate);
> -			break;
> -		}
> -
> -		mwait_hint = flg2MWAIT(cpuidle_state_table[cstate].flags);
> -		mwait_cstate = MWAIT_HINT2CSTATE(mwait_hint);
> -		mwait_substate = MWAIT_HINT2SUBSTATE(mwait_hint);
> -
> -		/* does the state exist in CPUID.MWAIT? */
> -		num_substates = (mwait_substates >> ((mwait_cstate + 1) * 4))
> -					& MWAIT_SUBSTATE_MASK;
> -
> -		/* if sub-state in table is not enumerated by CPUID */
> -		if ((mwait_substate + 1) > num_substates)
> -			continue;
> -
> -		dev->state_count += 1;
> -	}
> +	dev->state_count = drv->state_count;

The cpuidle_register_device function already does this initialization.

Probably you can get rid of this initialization and certainly factor out
a bit the code in this case.


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