Re: [PATCH v9 6/7] cpufreq: amd-pstate: introduce per CPU frequency boost control

["Limonciello, Mario" <mario.limonciello@amd.com>]

On 5/6/2024 5:19 AM, 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.

I don't think it should be "both" global and per CPU.  It should be one 
or the other (and I think per CPU is better).

> 
> The new sysfs attribute file is located at below path,
> `/sys/devices/system/cpu/cpuX/cpufreq/amd_pstate_boost_cpb`,
> where `X` represents the CPU number.
> 
> To disable CPB for a specific CPU, you can use the following command:
> $ sudo bash -c "echo 0 > /sys/devices/system/cpu/cpuX/cpufreq/amd_pstate_boost_cpb"
> 
> After disabling CPB, the CPU frequency will no longer boost beyond
> the base frequency for that particular CPU.
> 
> 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
> 
> ----------------------------------------------------------------------
> $ sudo bash -c "echo 0 > /sys/devices/system/cpu/cpu0/cpufreq/amd_pstate_boost_cpb"
> 
> 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
> 
> Please be aware that modifying the global variable
> `amd_pstate_global_params.cpb_boost` will overwrite the individual CPU settings.
> 
> Signed-off-by: Perry Yuan <perry.yuan@amd.com>
> ---
>   drivers/cpufreq/amd-pstate.c | 27 +++++++++++++++++++++++++++
>   1 file changed, 27 insertions(+)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 11bce2c1db32..44531711a5fa 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 state)
>   	return ret < 0 ? ret : 0;
>   }
>   
> +static ssize_t show_amd_pstate_boost_cpb(struct cpufreq_policy *policy, char *buf)
> +{
> +	struct amd_cpudata *cpudata = policy->driver_data;
> +	bool boost_val;
> +
> +	boost_val = READ_ONCE(cpudata->boost_state);
> +
> +	return sysfs_emit(buf, "%u\n", boost_val);
> +}
> +
> +static ssize_t store_amd_pstate_boost_cpb(
> +		struct cpufreq_policy *policy, const char *buf, size_t count)
> +{
> +	bool boost_val;
> +	int ret;
> +
> +	if (sscanf(buf, "%d", &boost_val) != 1)
> +		return -EINVAL;
> +
> +	ret = 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(amd_pstate_boost_cpb);
>   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[] = {
>   	&amd_pstate_highest_perf,
>   	&amd_pstate_prefcore_ranking,
>   	&amd_pstate_hw_prefcore,
> +	&amd_pstate_boost_cpb,
>   	NULL,
>   };
>   
> @@ -1437,6 +1463,7 @@ static struct freq_attr *amd_pstate_epp_attr[] = {
>   	&amd_pstate_hw_prefcore,
>   	&energy_performance_preference,
>   	&energy_performance_available_preferences,
> +	&amd_pstate_boost_cpb,
>   	NULL,
>   };
>