From: Mario Limonciello <mario.limonciello@amd.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@amd.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
@@ -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``.
+
+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
+	  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)
+{
+	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;
 
 	return ret ? ret : count;
 }
@@ -1364,6 +1440,32 @@ static ssize_t prefcore_show(struct device *dev,
 	return sysfs_emit(buf, "%s\n", str_enabled_disabled(amd_pstate_prefcore));
 }
 
+static ssize_t dynamic_epp_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%s\n", str_enabled_disabled(dynamic_epp));
+}
+
+static ssize_t dynamic_epp_store(struct device *a, struct device_attribute *b,
+				 const char *buf, size_t count)
+{
+	bool enabled;
+	int ret;
+
+	ret = kstrtobool(buf, &enabled);
+	if (ret)
+		return ret;
+
+	if (dynamic_epp == enabled)
+		return -EINVAL;
+
+	/* reinitialize with desired dynamic EPP value */
+	dynamic_epp = enabled;
+	ret = amd_pstate_change_driver_mode(cppc_state);
+
+	return ret ? ret : count;
+}
+
 cpufreq_freq_attr_ro(amd_pstate_max_freq);
 cpufreq_freq_attr_ro(amd_pstate_lowest_nonlinear_freq);
 
@@ -1374,6 +1476,7 @@ cpufreq_freq_attr_rw(energy_performance_preference);
 cpufreq_freq_attr_ro(energy_performance_available_preferences);
 static DEVICE_ATTR_RW(status);
 static DEVICE_ATTR_RO(prefcore);
+static DEVICE_ATTR_RW(dynamic_epp);
 
 static struct freq_attr *amd_pstate_attr[] = {
 	&amd_pstate_max_freq,
@@ -1398,6 +1501,7 @@ static struct freq_attr *amd_pstate_epp_attr[] = {
 static struct attribute *pstate_global_attributes[] = {
 	&dev_attr_status.attr,
 	&dev_attr_prefcore.attr,
+	&dev_attr_dynamic_epp.attr,
 	NULL
 };
 
@@ -1490,10 +1594,11 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
 	if (amd_pstate_acpi_pm_profile_server() ||
 	    amd_pstate_acpi_pm_profile_undefined()) {
 		policy->policy = CPUFREQ_POLICY_PERFORMANCE;
-		cpudata->epp_default = amd_pstate_get_epp(cpudata);
+		cpudata->epp_default_ac = cpudata->epp_default_dc = amd_pstate_get_epp(cpudata);
 	} else {
 		policy->policy = CPUFREQ_POLICY_POWERSAVE;
-		cpudata->epp_default = AMD_CPPC_EPP_BALANCE_PERFORMANCE;
+		cpudata->epp_default_ac = AMD_CPPC_EPP_PERFORMANCE;
+		cpudata->epp_default_dc = AMD_CPPC_EPP_BALANCE_PERFORMANCE;
 	}
 
 	if (cpu_feature_enabled(X86_FEATURE_CPPC)) {
@@ -1502,9 +1607,13 @@ 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)
+		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 +1630,8 @@ 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 +1667,10 @@ static int amd_pstate_epp_set_policy(struct cpufreq_policy *policy)
 	if (!policy->cpuinfo.max_freq)
 		return -ENODEV;
 
+	/* policy can't be changed to performance policy while dynamic epp is enabled */
+	if (policy->policy == CPUFREQ_POLICY_PERFORMANCE && 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;
 };
 
 /*
-- 
2.43.0

On 3/4/2025 8:53 PM, Mario Limonciello wrote:
> From: Mario Limonciello <mario.limonciello@amd.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@amd.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(-)
> 
[Snip]
> @@ -1556,6 +1667,10 @@ static int amd_pstate_epp_set_policy(struct cpufreq_policy *policy)
>  	if (!policy->cpuinfo.max_freq)
>  		return -ENODEV;
>  
> +	/* policy can't be changed to performance policy while dynamic epp is enabled */
> +	if (policy->policy == CPUFREQ_POLICY_PERFORMANCE && cpudata->dynamic_epp)
> +		return -EBUSY;

We might need to tweak this condition, because if we enable "CONFIG_X86_AMD_PSTATE_DYNAMIC_EPP" in config
and boot with "amd_pstate=active" it lands here (cpufreq_online()->amd_pstate_epp_set_policy()) driver init fails 
as the default governor is performance. 

> +
>  	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;
>  };
>  
>  /*

On 3/12/2025 07:16, Dhananjay Ugwekar wrote:
> On 3/4/2025 8:53 PM, Mario Limonciello wrote:
>> From: Mario Limonciello <mario.limonciello@amd.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@amd.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(-)
>>
> [Snip]
>> @@ -1556,6 +1667,10 @@ static int amd_pstate_epp_set_policy(struct cpufreq_policy *policy)
>>   	if (!policy->cpuinfo.max_freq)
>>   		return -ENODEV;
>>   
>> +	/* policy can't be changed to performance policy while dynamic epp is enabled */
>> +	if (policy->policy == CPUFREQ_POLICY_PERFORMANCE && cpudata->dynamic_epp)
>> +		return -EBUSY;
> 
> We might need to tweak this condition, because if we enable "CONFIG_X86_AMD_PSTATE_DYNAMIC_EPP" in config
> and boot with "amd_pstate=active" it lands here (cpufreq_online()->amd_pstate_epp_set_policy()) driver init fails
> as the default governor is performance.
> 

The check is important to make sure that you can't go to performance 
mode after init.

I think this is the way I would want to solve it.
Set policy to powersave before enabling dynamic epp for 
amd_pstate_epp_cpu_init().

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 824756ac0010e..4a0f561d0e2d1 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -1729,8 +1729,10 @@ static int amd_pstate_epp_cpu_init(struct 
cpufreq_policy *policy)
                 WRITE_ONCE(cpudata->cppc_req_cached, value);
         }

-       if (dynamic_epp)
+       if (dynamic_epp) {
+               policy->policy = CPUFREQ_POLICY_POWERSAVE;
                 ret = amd_pstate_set_dynamic_epp(policy);
+       }
         else
                 ret = amd_pstate_set_epp(policy, 
amd_pstate_get_balanced_epp(policy));
         if (ret)

Thoughts?

>> +
>>   	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;
>>   };
>>   
>>   /*
>

On 3/19/2025 1:06 AM, Mario Limonciello wrote:
> On 3/12/2025 07:16, Dhananjay Ugwekar wrote:
>> On 3/4/2025 8:53 PM, Mario Limonciello wrote:
>>> From: Mario Limonciello <mario.limonciello@amd.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@amd.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(-)
>>>
>> [Snip]
>>> @@ -1556,6 +1667,10 @@ static int amd_pstate_epp_set_policy(struct cpufreq_policy *policy)
>>>       if (!policy->cpuinfo.max_freq)
>>>           return -ENODEV;
>>>   +    /* policy can't be changed to performance policy while dynamic epp is enabled */
>>> +    if (policy->policy == CPUFREQ_POLICY_PERFORMANCE && cpudata->dynamic_epp)
>>> +        return -EBUSY;
>>
>> We might need to tweak this condition, because if we enable "CONFIG_X86_AMD_PSTATE_DYNAMIC_EPP" in config
>> and boot with "amd_pstate=active" it lands here (cpufreq_online()->amd_pstate_epp_set_policy()) driver init fails
>> as the default governor is performance.
>>
> 
> The check is important to make sure that you can't go to performance mode after init.
> 
> I think this is the way I would want to solve it.
> Set policy to powersave before enabling dynamic epp for amd_pstate_epp_cpu_init().
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 824756ac0010e..4a0f561d0e2d1 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -1729,8 +1729,10 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
>                 WRITE_ONCE(cpudata->cppc_req_cached, value);
>         }
> 
> -       if (dynamic_epp)
> +       if (dynamic_epp) {
> +               policy->policy = CPUFREQ_POLICY_POWERSAVE;
>                 ret = amd_pstate_set_dynamic_epp(policy);
> +       }
>         else
>                 ret = amd_pstate_set_epp(policy, amd_pstate_get_balanced_epp(policy));
			^^^^^^^^^^^^ (mentioned below)
>         if (ret)
> 
> Thoughts?

Yes, this looks good, because anyway there is no point in having performance governor and dynamic 
epp set at the same time.

I found one related quirk though, we are setting performance governor for server platforms in 
amd_pstate_epp_cpu_init() and then setting epp at the line highlighted above. We dont have a 
check in *_set_epp() functions for performance governor. This could alter the performance governor 
behavior if we set a "balanced" epp for it. I haven't tested this part yet. 

Thanks,
Dhananjay

> 
>>> +
>>>       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;
>>>   };
>>>     /*
>>
> 

On 3/18/2025 22:43, Dhananjay Ugwekar wrote:
> On 3/19/2025 1:06 AM, Mario Limonciello wrote:
>> On 3/12/2025 07:16, Dhananjay Ugwekar wrote:
>>> On 3/4/2025 8:53 PM, Mario Limonciello wrote:
>>>> From: Mario Limonciello <mario.limonciello@amd.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@amd.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(-)
>>>>
>>> [Snip]
>>>> @@ -1556,6 +1667,10 @@ static int amd_pstate_epp_set_policy(struct cpufreq_policy *policy)
>>>>        if (!policy->cpuinfo.max_freq)
>>>>            return -ENODEV;
>>>>    +    /* policy can't be changed to performance policy while dynamic epp is enabled */
>>>> +    if (policy->policy == CPUFREQ_POLICY_PERFORMANCE && cpudata->dynamic_epp)
>>>> +        return -EBUSY;
>>>
>>> We might need to tweak this condition, because if we enable "CONFIG_X86_AMD_PSTATE_DYNAMIC_EPP" in config
>>> and boot with "amd_pstate=active" it lands here (cpufreq_online()->amd_pstate_epp_set_policy()) driver init fails
>>> as the default governor is performance.
>>>
>>
>> The check is important to make sure that you can't go to performance mode after init.
>>
>> I think this is the way I would want to solve it.
>> Set policy to powersave before enabling dynamic epp for amd_pstate_epp_cpu_init().
>>
>> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
>> index 824756ac0010e..4a0f561d0e2d1 100644
>> --- a/drivers/cpufreq/amd-pstate.c
>> +++ b/drivers/cpufreq/amd-pstate.c
>> @@ -1729,8 +1729,10 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
>>                  WRITE_ONCE(cpudata->cppc_req_cached, value);
>>          }
>>
>> -       if (dynamic_epp)
>> +       if (dynamic_epp) {
>> +               policy->policy = CPUFREQ_POLICY_POWERSAVE;
>>                  ret = amd_pstate_set_dynamic_epp(policy);
>> +       }
>>          else
>>                  ret = amd_pstate_set_epp(policy, amd_pstate_get_balanced_epp(policy));
> 			^^^^^^^^^^^^ (mentioned below)
>>          if (ret)
>>
>> Thoughts?
> 
> Yes, this looks good, because anyway there is no point in having performance governor and dynamic
> epp set at the same time.
> 
> I found one related quirk though, we are setting performance governor for server platforms in
> amd_pstate_epp_cpu_init() and then setting epp at the line highlighted above. We dont have a
> check in *_set_epp() functions for performance governor. This could alter the performance governor
> behavior if we set a "balanced" epp for it. I haven't tested this part yet.

In that case we probably want the "default" ACPI platform profile to be 
"performance" when on a server instead of balanced.

> 
> Thanks,
> Dhananjay
> 
>>
>>>> +
>>>>        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;
>>>>    };
>>>>      /*
>>>
>>
> 

On 3/19/2025 11:50, Mario Limonciello wrote:
> On 3/18/2025 22:43, Dhananjay Ugwekar wrote:
>> On 3/19/2025 1:06 AM, Mario Limonciello wrote:
>>> On 3/12/2025 07:16, Dhananjay Ugwekar wrote:
>>>> On 3/4/2025 8:53 PM, Mario Limonciello wrote:
>>>>> From: Mario Limonciello <mario.limonciello@amd.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@amd.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(-)
>>>>>
>>>> [Snip]
>>>>> @@ -1556,6 +1667,10 @@ static int amd_pstate_epp_set_policy(struct 
>>>>> cpufreq_policy *policy)
>>>>>        if (!policy->cpuinfo.max_freq)
>>>>>            return -ENODEV;
>>>>>    +    /* policy can't be changed to performance policy while 
>>>>> dynamic epp is enabled */
>>>>> +    if (policy->policy == CPUFREQ_POLICY_PERFORMANCE && cpudata- 
>>>>> >dynamic_epp)
>>>>> +        return -EBUSY;
>>>>
>>>> We might need to tweak this condition, because if we enable 
>>>> "CONFIG_X86_AMD_PSTATE_DYNAMIC_EPP" in config
>>>> and boot with "amd_pstate=active" it lands here (cpufreq_online()- 
>>>> >amd_pstate_epp_set_policy()) driver init fails
>>>> as the default governor is performance.
>>>>
>>>
>>> The check is important to make sure that you can't go to performance 
>>> mode after init.
>>>
>>> I think this is the way I would want to solve it.
>>> Set policy to powersave before enabling dynamic epp for 
>>> amd_pstate_epp_cpu_init().
>>>
>>> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
>>> index 824756ac0010e..4a0f561d0e2d1 100644
>>> --- a/drivers/cpufreq/amd-pstate.c
>>> +++ b/drivers/cpufreq/amd-pstate.c
>>> @@ -1729,8 +1729,10 @@ static int amd_pstate_epp_cpu_init(struct 
>>> cpufreq_policy *policy)
>>>                  WRITE_ONCE(cpudata->cppc_req_cached, value);
>>>          }
>>>
>>> -       if (dynamic_epp)
>>> +       if (dynamic_epp) {
>>> +               policy->policy = CPUFREQ_POLICY_POWERSAVE;
>>>                  ret = amd_pstate_set_dynamic_epp(policy);
>>> +       }
>>>          else
>>>                  ret = amd_pstate_set_epp(policy, 
>>> amd_pstate_get_balanced_epp(policy));
>>             ^^^^^^^^^^^^ (mentioned below)
>>>          if (ret)
>>>
>>> Thoughts?
>>
>> Yes, this looks good, because anyway there is no point in having 
>> performance governor and dynamic
>> epp set at the same time.
>>
>> I found one related quirk though, we are setting performance governor 
>> for server platforms in
>> amd_pstate_epp_cpu_init() and then setting epp at the line highlighted 
>> above. We dont have a
>> check in *_set_epp() functions for performance governor. This could 
>> alter the performance governor
>> behavior if we set a "balanced" epp for it. I haven't tested this part 
>> yet.
> 
> In that case we probably want the "default" ACPI platform profile to be 
> "performance" when on a server instead of balanced.

Actually this is already done:

		cpudata->current_profile = PLATFORM_PROFILE_PERFORMANCE;

I'll post an updated patch series for you to test.

> 
>>
>> Thanks,
>> Dhananjay
>>
>>>
>>>>> +
>>>>>        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;
>>>>>    };
>>>>>      /*
>>>>
>>>
>>
> 

On 3/4/2025 8:53 PM, Mario Limonciello wrote:
> From: Mario Limonciello <mario.limonciello@amd.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@amd.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(-)
> 
[Snip]
> 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;

Is there an #ifdef needed here? I see build error when X86_AMD_PSTATE_DYNAMIC_EPP is not set in config

On 3/11/2025 01:34, Dhananjay Ugwekar wrote:
> On 3/4/2025 8:53 PM, Mario Limonciello wrote:
>> From: Mario Limonciello <mario.limonciello@amd.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@amd.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(-)
>>
> [Snip]
>> 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;
> 
> Is there an #ifdef needed here? I see build error when X86_AMD_PSTATE_DYNAMIC_EPP is not set in config
> 

Ah yeah, I see the same too when I check that config.  Not sure why 
build robot didn't catch this.

Will add this for next version.

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index dcf6e36d693f8..824756ac0010e 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -87,7 +87,11 @@ 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;
+#ifdef CONFIG_X86_AMD_PSTATE_DYNAMIC_EPP
  static bool dynamic_epp = CONFIG_X86_AMD_PSTATE_DYNAMIC_EPP;
+#else
+static bool dynamic_epp = false;
+#endif
  static struct quirk_entry *quirks;

  /*

Hello Mario,

On Tue, Mar 04, 2025 at 09:23:23AM -0600, Mario Limonciello wrote:
> From: Mario Limonciello <mario.limonciello@amd.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@amd.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.