linux-kernel - Re: [PATCH v3 11/21] cpufreq: amd: add amd-pstate frequencies attributes

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Date:   Fri, 5 Nov 2021 13:59:55 -0500
From:   Nathan Fontenot <nafonten@....com>
To:     Huang Rui <ray.huang@....com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Borislav Petkov <bp@...e.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Giovanni Gherdovich <ggherdovich@...e.cz>,
        linux-pm@...r.kernel.org
Cc:     Deepak Sharma <deepak.sharma@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Mario Limonciello <mario.limonciello@....com>,
        Steven Noonan <steven@...vesoftware.com>,
        Nathan Fontenot <nathan.fontenot@....com>,
        Jinzhou Su <Jinzhou.Su@....com>,
        Xiaojian Du <Xiaojian.Du@....com>,
        linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH v3 11/21] cpufreq: amd: add amd-pstate frequencies
 attributes

On 10/29/21 8:02 AM, Huang Rui wrote:
> Introduce sysfs attributes to get the different level processor
> frequencies.
> 
> Signed-off-by: Huang Rui <ray.huang@....com>
> ---
>  drivers/cpufreq/amd-pstate.c | 63 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 63 insertions(+)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 9af27ac1f818..8cf1e80f44e0 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -485,6 +485,68 @@ static int amd_pstate_cpu_exit(struct cpufreq_policy *policy)
>  	return 0;
>  }
>  
> +/* Sysfs attributes */
> +
> +/* This frequency is to indicate the maximum hardware frequency.
> + * If boost is not active but supported, the frequency will be larger than the
> + * one in cpuinfo.
> + */
> +static ssize_t show_amd_pstate_max_freq(struct cpufreq_policy *policy,
> +					char *buf)
> +{
> +	int max_freq;
> +	struct amd_cpudata *cpudata;
> +
> +	cpudata = policy->driver_data;
> +
> +	max_freq = amd_get_max_freq(cpudata);
> +	if (max_freq < 0)
> +		return max_freq;
> +
> +	return sprintf(&buf[0], "%u\n", max_freq);
> +}
> +
> +static ssize_t show_amd_pstate_nominal_freq(struct cpufreq_policy *policy,
> +					    char *buf)
> +{
> +	int nominal_freq;
> +	struct amd_cpudata *cpudata;
> +
> +	cpudata = policy->driver_data;
> +
> +	nominal_freq = amd_get_nominal_freq(cpudata);
> +	if (nominal_freq < 0)
> +		return nominal_freq;
> +
> +	return sprintf(&buf[0], "%u\n", nominal_freq);
> +}

The nominal_freq valus is already reported in sysfs by drivers/acpi since this
value is part of the ACPI spec. Is there a reason to have multiple sysfs entries 
for the same value?

-Nathan
 
> +
> +static ssize_t show_amd_pstate_lowest_nonlinear_freq(struct cpufreq_policy *policy,
> +						     char *buf)
> +{
> +	int freq;
> +	struct amd_cpudata *cpudata;
> +
> +	cpudata = policy->driver_data;
> +
> +	freq = amd_get_lowest_nonlinear_freq(cpudata);
> +	if (freq < 0)
> +		return freq;
> +
> +	return sprintf(&buf[0], "%u\n", freq);
> +}
> +
> +cpufreq_freq_attr_ro(amd_pstate_max_freq);
> +cpufreq_freq_attr_ro(amd_pstate_nominal_freq);
> +cpufreq_freq_attr_ro(amd_pstate_lowest_nonlinear_freq);
> +
> +static struct freq_attr *amd_pstate_attr[] = {
> +	&amd_pstate_max_freq,
> +	&amd_pstate_nominal_freq,
> +	&amd_pstate_lowest_nonlinear_freq,
> +	NULL,
> +};
> +
>  static struct cpufreq_driver amd_pstate_driver = {
>  	.flags		= CPUFREQ_CONST_LOOPS | CPUFREQ_NEED_UPDATE_LIMITS,
>  	.verify		= amd_pstate_verify,
> @@ -493,6 +555,7 @@ static struct cpufreq_driver amd_pstate_driver = {
>  	.exit		= amd_pstate_cpu_exit,
>  	.set_boost	= amd_pstate_set_boost,
>  	.name		= "amd-pstate",
> +	.attr           = amd_pstate_attr,
>  };
>  
>  static int __init amd_pstate_init(void)
>