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

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Message-ID: <ZKJzfbbMFRQO7xov@amd.com>
Date:   Mon, 3 Jul 2023 15:06:37 +0800
From:   Huang Rui <ray.huang@....com>
To:     "Limonciello, Mario" <Mario.Limonciello@....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 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,
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
>