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Message-ID: <186c3fa4-fe85-4989-9edd-fdb6345859a9@amd.com>
Date: Mon, 24 Mar 2025 13:49:26 +0530
From: Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>
To: Mario Limonciello <superm1@...nel.org>,
"Gautham R . Shenoy" <gautham.shenoy@....com>,
Perry Yuan <perry.yuan@....com>
Cc: "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<linux-kernel@...r.kernel.org>,
"open list:CPU FREQUENCY SCALING FRAMEWORK" <linux-pm@...r.kernel.org>,
Mario Limonciello <mario.limonciello@....com>
Subject: Re: [PATCH v4 1/5] cpufreq/amd-pstate: Add dynamic energy performance
preference
On 3/21/2025 7:58 AM, Mario Limonciello wrote:
> From: Mario Limonciello <mario.limonciello@....com>
>
> Dynamic energy performance preference will change the EPP profile
> based on whether the machine is running on AC or DC power.
>
> A notification chain from the power supply core is used to adjust
> EPP values on plug in or plug out events.
>
> For non-server systems:
> * the default EPP for AC mode is `performance`.
> * the default EPP for DC mode is `balance_performance`.
>
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> ---
> v3->v4:
> * Handle Kconfig not being set
> * Fix dynamic epp default on server
> v2-v3:
> * Fix typo in Kconfig
> v1->v2:
> * Change defaults to performance (AC) and balance_performance (DC)
> * Default Kconfig to disabled for now
> * Rebase on latest branch
> ---
> Documentation/admin-guide/pm/amd-pstate.rst | 18 ++-
> drivers/cpufreq/Kconfig.x86 | 12 ++
> drivers/cpufreq/amd-pstate.c | 135 +++++++++++++++++++-
> drivers/cpufreq/amd-pstate.h | 5 +-
> 4 files changed, 161 insertions(+), 9 deletions(-)
>
> diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst
> index 412423c54f258..2e076650dc77c 100644
> --- a/Documentation/admin-guide/pm/amd-pstate.rst
> +++ b/Documentation/admin-guide/pm/amd-pstate.rst
> @@ -289,7 +289,7 @@ and user can change current preference according to energy or performance needs
> Please get all support profiles list from
> ``energy_performance_available_preferences`` attribute, all the profiles are
> 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
> +firmware, but if the dynamic EPP feature is enabled, driver will block writes.
> This attribute is read-write.
>
> ``boost``
> @@ -311,6 +311,22 @@ boost or `1` to enable it, for the respective CPU using the sysfs path
> Other performance and frequency values can be read back from
> ``/sys/devices/system/cpu/cpuX/acpi_cppc/``, see :ref:`cppc_sysfs`.
>
> +Dynamic energy performance profile
> +==================================
> +The amd-pstate driver supports dynamically selecting the energy performance
> +profile based on whether the machine is running on AC or DC power.
> +
> +Whether this behavior is enabled by default with the kernel config option
> +`CONFIG_X86_AMD_PSTATE_DYNAMIC_EPP`. This behavior can also be overridden
> +at runtime by the sysfs file ``/sys/devices/system/cpu/cpufreq/policyX/dynamic_epp``.
The file is actually located at "/sys/devices/system/cpu/amd_pstate/dynamic_epp"
> +
> +When set to enabled, the driver will select a different energy performance
> +profile when the machine is running on battery or AC power.
> +When set to disabled, the driver will not change the energy performance profile
> +based on the power source and will not react to user desired power state.
> +
> +Attempting to manually write to the ``energy_performance_preference`` sysfs
> +file will fail when ``dynamic_epp`` is enabled.
>
> ``amd-pstate`` vs ``acpi-cpufreq``
> ======================================
[snip]
> @@ -1502,9 +1611,15 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
> return ret;
> WRITE_ONCE(cpudata->cppc_req_cached, value);
> }
> - ret = amd_pstate_set_epp(policy, cpudata->epp_default);
> +
> + if (dynamic_epp) {
> + policy->policy = CPUFREQ_POLICY_PERFORMANCE;
So, we are allowing the dynamic EPP framework to modify the EPP value in performance
governor as well? Shouldn't we allow dynamic_epp only with powersave governor.
> + ret = amd_pstate_set_dynamic_epp(policy);
> + }
> + else
> + ret = amd_pstate_set_epp(policy, amd_pstate_get_balanced_epp(policy));
> if (ret)
> - return ret;
> + goto free_cpudata1;
>
> current_pstate_driver->adjust_perf = NULL;
>
> @@ -1521,6 +1636,8 @@ static void amd_pstate_epp_cpu_exit(struct cpufreq_policy *policy)
> struct amd_cpudata *cpudata = policy->driver_data;
>
> if (cpudata) {
> + if (cpudata->dynamic_epp)
> + amd_pstate_clear_dynamic_epp(policy);
> kfree(cpudata);
> policy->driver_data = NULL;
> }
> @@ -1556,6 +1673,10 @@ static int amd_pstate_epp_set_policy(struct cpufreq_policy *policy)
> if (!policy->cpuinfo.max_freq)
> return -ENODEV;
>
> + /* policy can't be changed to powersave policy while dynamic epp is enabled */
> + if (policy->policy == CPUFREQ_POLICY_POWERSAVE && cpudata->dynamic_epp)
> + return -EBUSY;
> +
> cpudata->policy = policy->policy;
>
> ret = amd_pstate_epp_update_limit(policy);
> diff --git a/drivers/cpufreq/amd-pstate.h b/drivers/cpufreq/amd-pstate.h
> index fbe1c08d3f061..6882876f895de 100644
> --- a/drivers/cpufreq/amd-pstate.h
> +++ b/drivers/cpufreq/amd-pstate.h
> @@ -104,7 +104,10 @@ struct amd_cpudata {
> /* EPP feature related attributes*/
> u32 policy;
> bool suspended;
> - u8 epp_default;
> + u8 epp_default_ac;
> + u8 epp_default_dc;
> + bool dynamic_epp;
> + struct notifier_block power_nb;
> };
>
> /*
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