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From: Oleksandr Natalenko <oleksandr@natalenko.name>
To: rafael.j.wysocki@intel.com, Mario.Limonciello@amd.com,
 viresh.kumar@linaro.org, Ray.Huang@amd.com, gautham.shenoy@amd.com,
 Borislav.Petkov@amd.com, Perry Yuan <perry.yuan@amd.com>
Cc: Alexander.Deucher@amd.com, Xinmei.Huang@amd.com, Xiaojian.Du@amd.com,
 Li.Meng@amd.com, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject:
 Re: [PATCH v10 6/7] cpufreq: amd-pstate: introduce per CPU frequency boost
 control
Date: Wed, 08 May 2024 11:34:21 +0200
Message-ID: <12430678.O9o76ZdvQC@natalenko.name>
In-Reply-To:
 <49204c6d4a334c0bfbc589dda79b5cd7c4c28b7c.1715152592.git.perry.yuan@amd.com>
References:
 <cover.1715152592.git.perry.yuan@amd.com>
 <49204c6d4a334c0bfbc589dda79b5cd7c4c28b7c.1715152592.git.perry.yuan@amd.com>
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From: Oleksandr Natalenko <oleksandr@natalenko.name>
Date: Wed, 08 May 2024 11:34:21 +0200
Message-ID: <12430678.O9o76ZdvQC@natalenko.name>
MIME-Version: 1.0

Hello.

On st=C5=99eda 8. kv=C4=9Btna 2024 9:21:11, SEL=C4=8C Perry Yuan wrote:
> Add a new sysfs attribute file to support per CPU frequency boost
> control, allowing individual CPUs to enable or disable CPB separately.
>=20
> The new sysfs attribute file is located at below path,
> `/sys/devices/system/cpu/cpuX/cpufreq/boost`,
> where `X` represents the CPU number.
>=20
> To disable CPB for a specific CPU, you can use the following command:
> $ sudo bash -c "echo 0 > /sys/devices/system/cpu/cpuX/cpufreq/boost"
>=20
> After disabling CPB, the CPU frequency will no longer boost beyond
> the base frequency for that particular CPU.
>=20
> for example:
> ----------------------------------------------------------------------
> CPU NODE SOCKET CORE L1d:L1i:L2:L3 ONLINE    MAXMHZ   MINMHZ       MHZ
>   0    0      0    0 0:0:0:0          yes 4208.0000 400.0000 1666.7740
>   1    0      0    0 0:0:0:0          yes 4208.0000 400.0000  400.0000
>=20
> ----------------------------------------------------------------------
> $ sudo bash -c "echo 0 > /sys/devices/system/cpu/cpu0/cpufreq/boost"
>=20
> CPU NODE SOCKET CORE L1d:L1i:L2:L3 ONLINE    MAXMHZ   MINMHZ       MHZ
>   0    0      0    0 0:0:0:0          yes 3501.0000 400.0000 4154.3140
>   1    0      0    0 0:0:0:0          yes 4208.0000 400.0000  400.0000
>=20
> Please be aware that modifying the global variable
> `amd_pstate_global_params.cpb_boost` will overwrite the individual CPU se=
ttings.
>=20
> Signed-off-by: Perry Yuan <perry.yuan@amd.com>
> ---
>  drivers/cpufreq/amd-pstate.c | 27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
>=20
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 11bce2c1db32..cb0055e7c842 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -1371,6 +1371,30 @@ static int amd_pstate_cpu_boost(int cpu, bool stat=
e)
>  	return ret < 0 ? ret : 0;
>  }
> =20
> +static ssize_t show_boost(struct cpufreq_policy *policy, char *buf)
> +{
> +	struct amd_cpudata *cpudata =3D policy->driver_data;
> +	bool boost_val;
> +
> +	boost_val =3D READ_ONCE(cpudata->boost_state);
> +
> +	return sysfs_emit(buf, "%u\n", boost_val);
> +}
> +
> +static ssize_t store_boost(
> +		struct cpufreq_policy *policy, const char *buf, size_t count)
> +{
> +	bool boost_val;
> +	int ret;
> +
> +	if (sscanf(buf, "%d", &boost_val) !=3D 1)

This will generate warning. IIUC, sscanf() doesn't work with booleans direc=
tly, so you'd probably want to read the value into an (unsigned) integer, a=
nd then cast it to bool.

> +		return -EINVAL;
> +
> +	ret =3D amd_pstate_cpu_boost(policy->cpu, boost_val);
> +
> +	return ret < 0 ? ret : count;
> +}
> +
>  static ssize_t cpb_boost_show(struct device *dev,
>  			   struct device_attribute *attr, char *buf)
>  {
> @@ -1416,6 +1440,7 @@ cpufreq_freq_attr_ro(amd_pstate_prefcore_ranking);
>  cpufreq_freq_attr_ro(amd_pstate_hw_prefcore);
>  cpufreq_freq_attr_rw(energy_performance_preference);
>  cpufreq_freq_attr_ro(energy_performance_available_preferences);
> +cpufreq_freq_attr_rw(boost);
>  static DEVICE_ATTR_RW(status);
>  static DEVICE_ATTR_RO(prefcore);
>  static DEVICE_ATTR_RW(cpb_boost);
> @@ -1426,6 +1451,7 @@ static struct freq_attr *amd_pstate_attr[] =3D {
>  	&amd_pstate_highest_perf,
>  	&amd_pstate_prefcore_ranking,
>  	&amd_pstate_hw_prefcore,
> +	&boost,
>  	NULL,
>  };
> =20
> @@ -1437,6 +1463,7 @@ static struct freq_attr *amd_pstate_epp_attr[] =3D {
>  	&amd_pstate_hw_prefcore,
>  	&energy_performance_preference,
>  	&energy_performance_available_preferences,
> +	&boost,
>  	NULL,
>  };
> =20
>=20


=2D-=20
Oleksandr Natalenko (post-factum)
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