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

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Date:	Mon, 11 Mar 2013 01:29:01 +0000
From:	"Liu, Chuansheng" <chuansheng.liu@...el.com>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>
CC:	"lenb@...nel.org" <lenb@...nel.org>,
	"Brown, Len" <len.brown@...el.com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 2/3] intel_idle: Removing the redundant calculating for
 dev->state_count



> -----Original Message-----
> From: Daniel Lezcano [mailto:daniel.lezcano@...aro.org]
> Sent: Saturday, March 09, 2013 11:00 AM
> To: Liu, Chuansheng
> Cc: lenb@...nel.org; Brown, Len; 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.
Thanks your remind, will send patch V2 to remove it.

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