Re: [PATCH 4/7] powerpc/85xx: add support to JOG feature using cpufreq interface

[Zhao Chenhui <chenhui.zhao@freescale.com>]

On Mon, Nov 07, 2011 at 12:50:24PM -0600, Scott Wood wrote:
> On 11/07/2011 04:27 AM, Zhao Chenhui wrote:
> > On Fri, Nov 04, 2011 at 02:42:54PM -0500, Scott Wood wrote:
> >> On 11/04/2011 07:36 AM, Zhao Chenhui wrote:
> >>> +	cpufreq_frequency_table_target(policy,
> >>> +				       mpc85xx_freqs,
> >>> +				       target_freq,
> >>> +				       relation,
> >>> +				       &new);
> >>> +
> >>> +	freqs.old = policy->cur;
> >>> +	freqs.new = mpc85xx_freqs[new].frequency;
> >>> +	freqs.cpu = policy->cpu;
> >>> +
> >>> +	mutex_lock(&mpc85xx_switch_mutex);
> >>> +	cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
> >>> +
> >>> +	pr_info("Setting frequency for core %d to %d kHz, " \
> >>> +		 "PLL ratio is %d/2\n",
> >>> +		 policy->cpu,
> >>> +		 mpc85xx_freqs[new].frequency,
> >>> +		 mpc85xx_freqs[new].index);
> >>> +
> >>> +	set_pll(mpc85xx_freqs[new].index, policy->cpu);
> >>> +
> >>> +	cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
> >>> +	mutex_unlock(&mpc85xx_switch_mutex);
> >>> +
> >>> +	ppc_proc_freq = freqs.new * 1000ul;
> >>
> >> ppc_proc_freq is global -- can CPUs not have their frequencies adjusted
> >> separately?
> >>
> >> It should be under the lock, if the lock is needed at all.
> >>
> > 
> > There is only one ppc_proc_freq. no lock.
> 
> I realize there's only one.
> 
> I'm asking whether CPUs can have their frequencies set indpendently --
> if the answer is no, and this function is not specific to a CPU, my only
> concern is the lock.  Either this function can be called multiple times
> in parallel, in which case the ppc_proc_freq update should be inside the
> lock, or it can't, in which case why do we need the lock at all?
> 
> -Scott

Yes. They can be changed independently.
I will set ppc_proc_freq inside the lock.

-chenhui