linux-kernel - Re: [PATCH V2] acpi-cpufreq: replace per_cpu with driver

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Date:	Thu, 09 Jul 2015 09:28:30 +0800
From:	Pan Xinhui <xinhuix.pan@...el.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Viresh Kumar <viresh.kumar@...aro.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-pm@...r.kernel.org, "mnipxh@....com" <mnipxh@....com>,
	"yanmin_zhang@...ux.intel.com" <yanmin_zhang@...ux.intel.com>
Subject: Re: [PATCH V2] acpi-cpufreq: replace per_cpu with driver_data of
 policy

hi, Rafael
	thanks for your kind reply. :)

On 2015年07月09日 08:20, Rafael J. Wysocki wrote:
> On Tuesday, July 07, 2015 08:04:43 PM Viresh Kumar wrote:
>> On 07-07-15, 20:43, Pan Xinhui wrote:
>>>
>>> Drivers can store their internal per-policy information in
>>> policy->driver_data, lets use it.
>>>
>>> we have benefits after this replacing.
>>> 1) memory saving.
>>> 2) policy is shared by several cpus, per_cpu seems not correct. using
>>> *driver_data* is more reasonable.
>>> 3) fix a memory leak in acpi_cpufreq_cpu_exit. as policy->cpu might
>>> change during cpu hotplug. So sometimes we cant't free *data*, use
>>> *driver_data* to fix it.
>>> 4) fix a zero return value of get_cur_freq_on_cpu. Only per_cpu of
>>> policy->cpu is set to *data*, if we try to get cpufreq on other cpus, we
>>> get zero instead of correct values. Use *driver_data* to fix it.
>>>
>>> Signed-off-by: Pan Xinhui <xinhuix.pan@...el.com>
>>> ---
>>> Changes from V1:
>>> 	codes style fix, comments update
>>> 	move cpufreq_cpu_put(policy) after we get *driver_data*
>>> ---
>>>  drivers/cpufreq/acpi-cpufreq.c | 40 ++++++++++++++++++++++------------------
>>>  1 file changed, 22 insertions(+), 18 deletions(-)
>>
>> Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
> 
> OK
> 
> Does it fix any recent regressions or is it just an old bug?
> 

This patch achieve old bug fix and codes improvements. In past days, policy has no field *driver_data*, So
acpi-cpufreq driver has to use per_cpu to store some extra information. But it did not take good care of every scenarios.
Now cpufreq core makes awesome effort to store more per-policy information in policy. We can make use of this feature. So I
cook this patch. :)

I am preparing two patches for other two issues in acpi-cpufreq driver based on this patch.
I will fix them step by step. :)

thanks
xinhui

> Rafael
> 
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