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Message-ID: <Z8qWCyb8Jexb180g@BLRRASHENOY1.amd.com>
Date: Fri, 7 Mar 2025 12:15:31 +0530
From: "Gautham R. Shenoy" <gautham.shenoy@....com>
To: Mario Limonciello <superm1@...nel.org>
Cc: Perry Yuan <perry.yuan@....com>,
Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>,
"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 v2 1/5] cpufreq/amd-pstate: Add dynamic energy
performance preference
Hello Mario,
On Tue, Mar 04, 2025 at 09:23:23AM -0600, 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>
> ---
> 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 | 129 ++++++++++++++++++--
> drivers/cpufreq/amd-pstate.h | 5 +-
> 4 files changed, 155 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
[...snip..]
> @@ -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``.
> +
> +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``
> ======================================
> diff --git a/drivers/cpufreq/Kconfig.x86 b/drivers/cpufreq/Kconfig.x86
> index 97c2d4f15d76e..c5ef92634ddf4 100644
> --- a/drivers/cpufreq/Kconfig.x86
> +++ b/drivers/cpufreq/Kconfig.x86
> @@ -68,6 +68,18 @@ config X86_AMD_PSTATE_DEFAULT_MODE
> For details, take a look at:
> <file:Documentation/admin-guide/pm/amd-pstate.rst>.
>
> +config X86_AMD_PSTATE_DYNAMIC_EPP
> + bool "AMD Processor P-State dynamic EPP support"
> + depends on X86_AMD_PSTATE
> + default n
> + help
> + Allow the kenrel to dynamically change the energy performance
^^^^^^
kernel
> + value from events like ACPI platform profile and AC adapter plug
> + events.
> +
> + This feature can also be changed at runtime, this configuration
> + option only sets the kernel default value behavior.
> +
> config X86_AMD_PSTATE_UT
> tristate "selftest for AMD Processor P-State driver"
> depends on X86 && ACPI_PROCESSOR
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index e98ef41083ba1..f00fb4ba9f26e 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -36,6 +36,7 @@
> #include <linux/io.h>
> #include <linux/delay.h>
> #include <linux/uaccess.h>
> +#include <linux/power_supply.h>
> #include <linux/static_call.h>
> #include <linux/topology.h>
>
> @@ -86,6 +87,7 @@ static struct cpufreq_driver amd_pstate_driver;
> static struct cpufreq_driver amd_pstate_epp_driver;
> static int cppc_state = AMD_PSTATE_UNDEFINED;
> static bool amd_pstate_prefcore = true;
> +static bool dynamic_epp = CONFIG_X86_AMD_PSTATE_DYNAMIC_EPP;
> static struct quirk_entry *quirks;
>
> /*
> @@ -1050,6 +1052,73 @@ static void amd_pstate_cpu_exit(struct cpufreq_policy *policy)
> kfree(cpudata);
> }
>
> +static int amd_pstate_get_balanced_epp(struct cpufreq_policy *policy)
Can we rename this function as amd_pstate_get_dynamic_epp() ?
Because the values being returned may not be
balance_performance/balance_power.
> +{
> + struct amd_cpudata *cpudata = policy->driver_data;
> +
> + if (power_supply_is_system_supplied())
> + return cpudata->epp_default_ac;
> + else
> + return cpudata->epp_default_dc;
> +}
> +
> +static int amd_pstate_power_supply_notifier(struct notifier_block *nb,
> + unsigned long event, void *data)
> +{
> + struct amd_cpudata *cpudata = container_of(nb, struct amd_cpudata, power_nb);
> + struct cpufreq_policy *policy __free(put_cpufreq_policy) = cpufreq_cpu_get(cpudata->cpu);
> + u8 epp;
> + int ret;
> +
> + if (event != PSY_EVENT_PROP_CHANGED)
> + return NOTIFY_OK;
> +
> + epp = amd_pstate_get_balanced_epp(policy);
> +
> + ret = amd_pstate_set_epp(policy, epp);
> + if (ret)
> + pr_warn("Failed to set CPU %d EPP %u: %d\n", cpudata->cpu, epp, ret);
> +
> + return NOTIFY_OK;
> +}
> +static void amd_pstate_clear_dynamic_epp(struct cpufreq_policy *policy)
> +{
> + struct amd_cpudata *cpudata = policy->driver_data;
> +
> + if (cpudata->power_nb.notifier_call)
> + power_supply_unreg_notifier(&cpudata->power_nb);
> + cpudata->dynamic_epp = false;
> +}
> +
> +static int amd_pstate_set_dynamic_epp(struct cpufreq_policy *policy)
> +{
> + struct amd_cpudata *cpudata = policy->driver_data;
> + int ret;
> + u8 epp;
> +
> + epp = amd_pstate_get_balanced_epp(policy);
> + ret = amd_pstate_set_epp(policy, epp);
> + if (ret)
> + return ret;
> +
> + /* only enable notifier if things will actually change */
> + if (cpudata->epp_default_ac != cpudata->epp_default_dc) {
> + ret = power_supply_reg_notifier(&cpudata->power_nb);
> + if (ret)
> + goto cleanup;
> + cpudata->power_nb.notifier_call = amd_pstate_power_supply_notifier;
> + }
> +
> + cpudata->dynamic_epp = true;
> +
> + return 0;
> +
> +cleanup:
> + amd_pstate_clear_dynamic_epp(policy);
> +
> + return ret;
> +}
> +
> /* Sysfs attributes */
>
> /*
> @@ -1146,6 +1215,11 @@ static ssize_t store_energy_performance_preference(
> ssize_t ret;
> u8 epp;
>
> + if (cpudata->dynamic_epp) {
> + pr_debug("EPP cannot be set when dynamic EPP is enabled\n");
> + return -EBUSY;
> + }
> +
> ret = sscanf(buf, "%20s", str_preference);
> if (ret != 1)
> return -EINVAL;
> @@ -1154,10 +1228,10 @@ static ssize_t store_energy_performance_preference(
> if (ret < 0)
> return -EINVAL;
>
> - if (!ret)
> - epp = cpudata->epp_default;
> - else
> + if (ret)
> epp = epp_values[ret];
> + else
> + epp = amd_pstate_get_balanced_epp(policy);
>
> if (epp > 0 && policy->policy == CPUFREQ_POLICY_PERFORMANCE) {
> pr_debug("EPP cannot be set under performance policy\n");
> @@ -1165,6 +1239,8 @@ static ssize_t store_energy_performance_preference(
> }
>
> ret = amd_pstate_set_epp(policy, epp);
> + if (ret)
> + return ret;
Isn't this unecessary given that the next line is doing exactly this ?
>
> return ret ? ret : count;
> }
Rest of the patch looks good to me.
--
Thanks and Regards
gautham.
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