linux-kernel - Re: [PATCH] cpufreq: respect the min/max settings from user space

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Message-ID: <544F0C8C.3090003@nvidia.com>
Date:	Tue, 28 Oct 2014 11:25:00 +0800
From:	Vince Hsu <vinceh@...dia.com>
To:	Viresh Kumar <viresh.kumar@...aro.org>
CC:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Bill Huang <bilhuang@...dia.com>, <dgreid@...gle.com>,
	<olofj@...omium.org>
Subject: Re: [PATCH] cpufreq: respect the min/max settings from user space

Hi Viresh,

Could you remind me where can I find this patch upstream? It seems this 
was missed?

Thanks,
Vince

On 10/06/2014 12:50 PM, Vince Hsu wrote:
> Hi Viresh,
>
> On 10/06/2014 12:45 PM, Viresh Kumar wrote:
>> On 2 October 2014 12:25, Vince Hsu <vinceh@...dia.com> wrote:
>>> When the user space tries to set scaling_(max|min)_freq through
>>> sysfs, the cpufreq_set_policy() asks other driver's opinions
>>> for the max/min frequencies. Some device drivers, like Tegra
>>> CPU EDP which is not upstreamed yet though, may constrain the
>>> CPU maximum frequency dynamically because of board design.
>>> So if the user space access happens and some driver is capping
>>> the cpu frequency at the same time, the user_policy->(max|min)
>>> is overridden by the capped value, and that's not expected by
>>> the user space. And if the user space is not invoked again,
>>> the CPU will always be capped by the user_policy->(max|min)
>>> even no drivers limit the CPU frequency any more.
>>>
>>> This patch preserves the user specified min/max settings, so that
>>> every time the cpufreq policy is updated, the new max/min can
>>> be re-evaluated correctly based on the user's expection and
>>> the present device drivers' status.
>>>
>>> Signed-off-by: Vince Hsu <vinceh@...dia.com>
>>> ---
>>> Hi,
>>>
>>> I'm not sure if any platform that is supported mainlin might have this
>>> issue, and this patch is complie tested only.
>> Why only compiled tested? Why haven't you tested it on tegra?
> I did test with Chrome kernel on Tegra platform. I can't do that with 
> mainline kernel because we haven't had the CPU EDP driver upstream yet.
>
> Thanks,
> Vince
>
>>
>>>   drivers/cpufreq/cpufreq.c | 6 ++++--
>>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
>>> index 24bf76fba141..c007cf2a3d2a 100644
>>> --- a/drivers/cpufreq/cpufreq.c
>>> +++ b/drivers/cpufreq/cpufreq.c
>>> @@ -524,7 +524,7 @@ static int cpufreq_set_policy(struct 
>>> cpufreq_policy *policy,
>>>   static ssize_t 
>>> store_##file_name                                       \
>>>   (struct cpufreq_policy *policy, const char *buf, size_t 
>>> count)         \
>>> { \
>>> -       int 
>>> ret;                                                        \
>>> +       int ret, temp;                                          \
>>>          struct cpufreq_policy 
>>> new_policy;                               \
>>> \
>>>          ret = cpufreq_get_policy(&new_policy, 
>>> policy->cpu);             \
>>> @@ -535,8 +535,10 @@ static ssize_t 
>>> store_##file_name                                   \
>>>          if (ret != 
>>> 1)                                                   \
>>>                  return 
>>> -EINVAL;                                         \
>>> \
>>> +       temp = 
>>> new_policy.object;                                       \
>>>          ret = cpufreq_set_policy(policy, &new_policy);          \
>>> -       policy->user_policy.object = 
>>> policy->object;                    \
>>> +       if 
>>> (!ret)                                                       \
>>> +               policy->user_policy.object = 
>>> temp;                      \
>>> \
>>>          return ret ? ret : 
>>> count;                                       \
>>>   }
>> Looks fine otherwise.
>>
>> Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
>
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