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Message-ID: <1369cedf-e66b-82eb-4501-a6976bb8c558@huawei.com>
Date:   Thu, 26 Oct 2023 10:36:15 +0800
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Subject: Re: [PATCH -next] cpufreq: userspace: Keep the current frequency when
 set userspace policy
Content-Language: en-US
To:     Viresh Kumar <viresh.kumar@linaro.org>
CC:     <rafael@kernel.org>, <liwei391@huawei.com>,
        <linux-pm@vger.kernel.org>, <xiexiuqi@huawei.com>,
        <wangxiongfeng2@huawei.com>, <linux-kernel@vger.kernel.org>
References: <20231025080910.3245690-1-zengheng4@huawei.com>
 <20231025111821.pp3hdpilddbx4yzr@vireshk-i7>
From:   Zeng Heng <zengheng4@huawei.com>
In-Reply-To: <20231025111821.pp3hdpilddbx4yzr@vireshk-i7>
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在 2023/10/25 19:18, Viresh Kumar 写道:
> On 25-10-23, 16:09, Zeng Heng wrote:
>> When switching to the userspace policy, if the current frequency is within
>> the range of policy's min and max values, the current frequency value
>> should be remained. The .limit() function is called when changing governor
>> or updating governor limits, so in both cases, there is no need to update
>> frequency if the current frequency does not exceed the threshold.
>>
>> Additionally, when changing to userspace governor, the default value of
>> set_speed is set by reading the current frequency of the CPU, but there
>> is inevitable error between the frequency coming from .get_rate() interface
>> and the actual working frequency. Consequently, when switching to userspace
>> policy, keeping the current frequency can avoid unexpected changes.
>>
>> Signed-off-by: Zeng Heng <zengheng4@huawei.com>
>> ---
>>   drivers/cpufreq/cpufreq_userspace.c | 4 +---
>>   1 file changed, 1 insertion(+), 3 deletions(-)
>>
>> diff --git a/drivers/cpufreq/cpufreq_userspace.c b/drivers/cpufreq/cpufreq_userspace.c
>> index 2c42fee76daa..fe55a7bb663c 100644
>> --- a/drivers/cpufreq/cpufreq_userspace.c
>> +++ b/drivers/cpufreq/cpufreq_userspace.c
>> @@ -117,9 +117,7 @@ static void cpufreq_userspace_policy_limits(struct cpufreq_policy *policy)
>>   	else if (policy->min > userspace->setspeed)
>>   		__cpufreq_driver_target(policy, policy->min,
>>   					CPUFREQ_RELATION_L);
>> -	else
>> -		__cpufreq_driver_target(policy, userspace->setspeed,
>> -					CPUFREQ_RELATION_L);
>> +	/* Otherwise, keep the current frequency. */
>>
>>   	mutex_unlock(&userspace->mutex);
>>   }
> Here is some reasoning why it should be done the way it is:
>
> commit e43e94c1eda7 ("cpufreq: Fix GOV_LIMITS handling for the userspace governor")


Get it, thanks for the response.

Zeng Heng