linux-kernel - Re: [PATCH] cpufreq: CPPC: Support for autonomous selection in cppc

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Message-ID: <4c4b0140-9126-4586-92f8-f7c9fd7a4a34@huawei.com>
Date: Mon, 19 May 2025 17:29:22 +0800
From: "zhenglifeng (A)" <zhenglifeng1@...wei.com>
To: Viresh Kumar <viresh.kumar@...aro.org>
CC: <rafael@...nel.org>, <pierre.gondois@....com>, <sumitg@...dia.com>,
	<linux-kernel@...r.kernel.org>, <linux-pm@...r.kernel.org>,
	<linuxarm@...wei.com>, <mario.limonciello@....com>,
	<yumpusamongus@...il.com>, <srinivas.pandruvada@...ux.intel.com>,
	<jonathan.cameron@...wei.com>, <zhanjie9@...ilicon.com>,
	<lihuisong@...wei.com>, <cenxinghai@...artners.com>, <yubowen8@...wei.com>,
	<hepeng68@...wei.com>
Subject: Re: [PATCH] cpufreq: CPPC: Support for autonomous selection in
 cppc_cpufreq

On 2025/5/19 16:18, Viresh Kumar wrote:
> On 07-05-25, 11:19, Lifeng Zheng wrote:
>> Add sysfs interfaces for CPPC autonomous selection in the cppc_cpufreq
>> driver.
>>
>> Signed-off-by: Lifeng Zheng <zhenglifeng1@...wei.com>
> 
> Sumit, can you provide your tag if it looks fine to you ?
> 
>> diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
>> index 206079d3bd5b..37065e1b8ebc 100644
>> --- a/Documentation/ABI/testing/sysfs-devices-system-cpu
>> +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
>> @@ -268,6 +268,60 @@ Description:	Discover CPUs in the same CPU frequency coordination domain
>>  		This file is only present if the acpi-cpufreq or the cppc-cpufreq
>>  		drivers are in use.
>>  
>> +What:		/sys/devices/system/cpu/cpuX/cpufreq/auto_select
> 
> Is the path correct? Should this be cpufreq/policyN/auto_select ?

cpufreq/policyN/ is linked to cpuX/cpufreq/, both paths correct. The
description of freqdomain_cpus uses cpuX/cpufreq/, so I followed.

> 
>> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
>> index b3d74f9adcf0..3c3d00cec298 100644
>> --- a/drivers/cpufreq/cppc_cpufreq.c
>> +++ b/drivers/cpufreq/cppc_cpufreq.c
>> @@ -808,10 +808,119 @@ static ssize_t show_freqdomain_cpus(struct cpufreq_policy *policy, char *buf)
>>  
>>  	return cpufreq_show_cpus(cpu_data->shared_cpu_map, buf);
>>  }
>> +
>> +static ssize_t show_auto_select(struct cpufreq_policy *policy, char *buf)
>> +{
>> +	bool val;
>> +	int ret;
>> +
>> +	ret = cppc_get_auto_sel(policy->cpu, &val);
>> +
>> +	/* show "<unsupported>" when this register is not supported by cpc */
> 
> s/cpc/cppc/ ?

It means Continuous Performance Control, you can see that in ACPI 6.5,
s8.4.6.1 _CPC (Continuous Performance Control). Use "_CPC" might be better.