linux-kernel - Re: [PATCH] cpufreq: amd-pstate: Add sysfs file for base frequency

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Date:   Mon, 3 Jul 2023 20:09:19 -0500
From:   Mario Limonciello <mario.limonciello@....com>
To:     Huang Rui <ray.huang@....com>
Cc:     "rafael@...nel.org" <rafael@...nel.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Karny, Wyes" <Wyes.Karny@....com>,
        "Yuan, Perry" <Perry.Yuan@....com>
Subject: Re: [PATCH] cpufreq: amd-pstate: Add sysfs file for base frequency

On 7/3/23 02:06, Huang Rui wrote:
> On Thu, Jun 29, 2023 at 09:54:54PM +0800, Limonciello, Mario wrote:
>> Some applications may want to query the base frequency to tell when
>> a processor is operating in boost.
>>
>> Tested-by: Wyes Karny <wyes.karny@....com>
>> Reviewed-by: Wyes Karny <wyes.karny@....com>
>> Co-developed-by: Perry Yuan <perry.yuan@....com>
>> Signed-off-by: Perry Yuan <perry.yuan@....com>
>> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
>> ---
>>   Documentation/admin-guide/pm/amd-pstate.rst |  4 ++++
>>   drivers/cpufreq/amd-pstate.c                | 15 +++++++++++++++
>>   2 files changed, 19 insertions(+)
>>
>> diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst
>> index 1cf40f69278cd..e68267857e859 100644
>> --- a/Documentation/admin-guide/pm/amd-pstate.rst
>> +++ b/Documentation/admin-guide/pm/amd-pstate.rst
>> @@ -281,6 +281,10 @@ integer values defined between 0 to 255 when EPP feature is enabled by platform
>>   firmware, if EPP feature is disabled, driver will ignore the written value
>>   This attribute is read-write.
>>   
>> +``base_frequency``
>> +	Shows the base frequency of the CPU. Frequencies above this will be in the
>> +  ``boost`` range. This attribute is read-only.
>> +
>>   Other performance and frequency values can be read back from
>>   ``/sys/devices/system/cpu/cpuX/acpi_cppc/``, see :ref:`cppc_sysfs`.
>>   
>> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
>> index 81fba0dcbee99..0fec66b3f7241 100644
>> --- a/drivers/cpufreq/amd-pstate.c
>> +++ b/drivers/cpufreq/amd-pstate.c
>> @@ -1037,6 +1037,19 @@ static ssize_t store_status(struct kobject *a, struct kobj_attribute *b,
>>   	return ret < 0 ? ret : count;
>>   }
>>   
>> +static ssize_t show_base_frequency(struct cpufreq_policy *policy, char *buf)
>> +{
>> +	struct amd_cpudata *cpudata = policy->driver_data;
>> +	u32 nominal_freq;
>> +
>> +	nominal_freq = amd_get_nominal_freq(cpudata);
>> +	if (nominal_freq < 0)
>> +		return nominal_freq;
>> +
>> +	return sysfs_emit(buf, "%d\n", nominal_freq);
>> +}
> 
> User can get it from nominal_freq at drivers/acpi/cppc_acpi.c:
> 
> show_cppc_data(cppc_get_perf_caps, cppc_perf_caps, nominal_freq);

Thanks for sharing that, I wasn't aware.  This patch is unnecessary indeed.

> 
> Thanks,
> Ray
> 
>> +
>> +cpufreq_freq_attr_ro(base_frequency);
>>   cpufreq_freq_attr_ro(amd_pstate_max_freq);
>>   cpufreq_freq_attr_ro(amd_pstate_lowest_nonlinear_freq);
>>   
>> @@ -1049,6 +1062,7 @@ static struct freq_attr *amd_pstate_attr[] = {
>>   	&amd_pstate_max_freq,
>>   	&amd_pstate_lowest_nonlinear_freq,
>>   	&amd_pstate_highest_perf,
>> +	&base_frequency,
>>   	NULL,
>>   };
>>   
>> @@ -1058,6 +1072,7 @@ static struct freq_attr *amd_pstate_epp_attr[] = {
>>   	&amd_pstate_highest_perf,
>>   	&energy_performance_preference,
>>   	&energy_performance_available_preferences,
>> +	&base_frequency,
>>   	NULL,
>>   };
>>   
>> -- 
>> 2.34.1
>>