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Date:   Tue, 29 Nov 2022 18:18:57 +0530
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Subject: Re: [PATCH v5 3/9] cpufreq: amd_pstate: implement Pstate EPP support
 for the AMD processors
Content-Language: en-US
To:     Perry Yuan <perry.yuan@amd.com>, rafael.j.wysocki@intel.com,
        Mario.Limonciello@amd.com, ray.huang@amd.com,
        viresh.kumar@linaro.org
Cc:     Deepak.Sharma@amd.com, Nathan.Fontenot@amd.com,
        Alexander.Deucher@amd.com, Shimmer.Huang@amd.com,
        Xiaojian.Du@amd.com, Li.Meng@amd.com, linux-pm@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20221128170314.2276636-1-perry.yuan@amd.com>
 <20221128170314.2276636-4-perry.yuan@amd.com>
From:   Wyes Karny <wyes.karny@amd.com>
In-Reply-To: <20221128170314.2276636-4-perry.yuan@amd.com>
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Hi Perry,

On 11/28/2022 10:33 PM, Perry Yuan wrote:
> From: Perry Yuan <Perry.Yuan@amd.com>
> 
> Add EPP driver support for AMD SoCs which support a dedicated MSR for
> CPPC.  EPP is used by the DPM controller to configure the frequency that
> a core operates at during short periods of activity.
> 
> The SoC EPP targets are configured on a scale from 0 to 255 where 0
> represents maximum performance and 255 represents maximum efficiency.
> 
> The amd-pstate driver exports profile string names to userspace that are
> tied to specific EPP values.
> 
> The balance_performance string (0x80) provides the best balance for
> efficiency versus power on most systems, but users can choose other
> strings to meet their needs as well.
> 
> $ cat /sys/devices/system/cpu/cpufreq/policy0/energy_performance_available_preferences
> default performance balance_performance balance_power power
> 
> $ cat /sys/devices/system/cpu/cpufreq/policy0/energy_performance_preference
> balance_performance
> 
> Signed-off-by: Perry Yuan <Perry.Yuan@amd.com>
> ---
>  drivers/cpufreq/amd-pstate.c | 635 ++++++++++++++++++++++++++++++++++-
>  include/linux/amd-pstate.h   |  81 +++++
>  2 files changed, 710 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 204e39006dda..5a19b832afdf 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -59,8 +59,132 @@
>   * we disable it by default to go acpi-cpufreq on these processors and add a
>   * module parameter to be able to enable it manually for debugging.
>   */
> -static struct cpufreq_driver amd_pstate_driver;
> +static bool shared_mem __read_mostly;

`shared_mem` is initialized to 0 here but it is not being overwite anywhere.

> +static int cppc_active __read_mostly;
>  static int cppc_load __initdata;
> +static int epp_off __initdata;

Not sure why we need `cppc_active` and `epp_off` two veriables to control `active mode`.
Is is because `epp_off` is marked as __initdata, therefore if you read `epp_off` in non-init functions
it shows zero?
In that case, can we remove __initdata from `epp_off` and use this same variable elsewhere?

> +
> +static struct cpufreq_driver *default_pstate_driver;
> +static struct amd_cpudata **all_cpu_data;
> +
> +static struct amd_pstate_params global_params;
> +
> +static DEFINE_MUTEX(amd_pstate_limits_lock);
> +static DEFINE_MUTEX(amd_pstate_driver_lock);
> +
> +static bool cppc_boost __read_mostly;
> +struct kobject *amd_pstate_kobj;
> +
> +#ifdef CONFIG_ACPI_CPPC_LIB
> +static s16 amd_pstate_get_epp(struct amd_cpudata *cpudata, u64 cppc_req_cached)
> +{
> +	s16 epp;
> +	struct cppc_perf_caps perf_caps;
> +	int ret;
> +
> +	if (boot_cpu_has(X86_FEATURE_CPPC)) {
> +		if (!cppc_req_cached) {
> +			epp = rdmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ,
> +					&cppc_req_cached);
> +			if (epp)
> +				return epp;
> +		}
> +		epp = (cppc_req_cached >> 24) & 0xFF;
> +	} else {
> +		ret = cppc_get_epp_caps(cpudata->cpu, &perf_caps);
> +		if (ret < 0) {
> +			pr_debug("Could not retrieve energy perf value (%d)\n", ret);
> +			return -EIO;
> +		}
> +		epp = (s16) perf_caps.energy_perf;
> +	}
> +
> +	return epp;
> +}
> +#endif
> +
> +static int amd_pstate_get_energy_pref_index(struct amd_cpudata *cpudata)
> +{
> +	s16 epp;
> +	int index = -EINVAL;
> +
> +	epp = amd_pstate_get_epp(cpudata, 0);
> +	if (epp < 0)
> +		return epp;
> +
> +	switch (epp) {
> +		case AMD_CPPC_EPP_PERFORMANCE:
> +			index = EPP_INDEX_PERFORMANCE;
> +			break;
> +		case AMD_CPPC_EPP_BALANCE_PERFORMANCE:
> +			index = EPP_INDEX_BALANCE_PERFORMANCE;
> +			break;
> +		case AMD_CPPC_EPP_BALANCE_POWERSAVE:
> +			index = EPP_INDEX_BALANCE_POWERSAVE;
> +			break;
> +		case AMD_CPPC_EPP_POWERSAVE:
> +			index = EPP_INDEX_POWERSAVE;
> +			break;
> +		default:
> +			break;
> +	}
> +
> +	return index;
> +}
> +
> +#ifdef CONFIG_ACPI_CPPC_LIB
> +static int amd_pstate_set_epp(struct amd_cpudata *cpudata, u32 epp)
> +{
> +	int ret;
> +	struct cppc_perf_ctrls perf_ctrls;
> +
> +	if (boot_cpu_has(X86_FEATURE_CPPC)) {
> +		u64 value = READ_ONCE(cpudata->cppc_req_cached);
> +
> +		value &= ~GENMASK_ULL(31, 24);
> +		value |= (u64)epp << 24;

small nit, AMD_CPPC_ENERGY_PERF_PREF macro can be used here, instead of hardcoding values.

> +		WRITE_ONCE(cpudata->cppc_req_cached, value);
> +
> +		ret = wrmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, value);
> +		if (!ret)
> +			cpudata->epp_cached = epp;
> +	} else {
> +		perf_ctrls.energy_perf = epp;
> +		ret = cppc_set_epp_perf(cpudata->cpu, &perf_ctrls, 1);
> +		if (ret) {
> +			pr_debug("failed to set energy perf value (%d)\n", ret);
> +			return ret;
> +		}
> +		cpudata->epp_cached = epp;
> +	}
> +
> +	return ret;
> +}
> +
> +static int amd_pstate_set_energy_pref_index(struct amd_cpudata *cpudata,
> +		int pref_index)
> +{
> +	int epp = -EINVAL;
> +	int ret;
> +
> +	if (!pref_index) {
> +		pr_debug("EPP pref_index is invalid\n");
> +		return -EINVAL;
> +	}
> +
> +	if (epp == -EINVAL)
> +		epp = epp_values[pref_index];
> +
> +	if (epp > 0 && cpudata->policy == CPUFREQ_POLICY_PERFORMANCE) {
> +		pr_debug("EPP cannot be set under performance policy\n");
> +		return -EBUSY;
> +	}
> +
> +	ret = amd_pstate_set_epp(cpudata, epp);
> +
> +	return ret;
> +}
> +#endif
>  
>  static inline int pstate_enable(bool enable)
>  {
> @@ -70,11 +194,21 @@ static inline int pstate_enable(bool enable)
>  static int cppc_enable(bool enable)
>  {
>  	int cpu, ret = 0;
> +	struct cppc_perf_ctrls perf_ctrls;
>  
>  	for_each_present_cpu(cpu) {
>  		ret = cppc_set_enable(cpu, enable);
>  		if (ret)
>  			return ret;
> +
> +		/* Enable autonomous mode for EPP */
> +		if (!cppc_active) {

It should be: if (cppc_active) {   right?

> +			/* Set desired perf as zero to allow EPP firmware control */
> +			perf_ctrls.desired_perf = 0;
> +			ret = cppc_set_perf(cpu, &perf_ctrls);

Don't we have to do same thing (setting des_perf to 0) in `pstate_enable` function?
Because for active + MSR supported processors will invoke `pstate_enable` function.

> +			if (ret)
> +				return ret;
> +		}

>  	}
>  
>  	return ret;
> @@ -417,7 +551,7 @@ static void amd_pstate_boost_init(struct amd_cpudata *cpudata)
>  		return;
>  
>  	cpudata->boost_supported = true;
> -	amd_pstate_driver.boost_enabled = true;
> +	default_pstate_driver->boost_enabled = true;
>  }
>  
>  static void amd_perf_ctl_reset(unsigned int cpu)
> @@ -591,10 +725,61 @@ static ssize_t show_amd_pstate_highest_perf(struct cpufreq_policy *policy,
>  	return sprintf(&buf[0], "%u\n", perf);
>  }
>  
> +static ssize_t show_energy_performance_available_preferences(
> +				struct cpufreq_policy *policy, char *buf)
> +{
> +	int i = 0;
> +	int ret = 0;
> +
> +	while (energy_perf_strings[i] != NULL)
> +		ret += sprintf(&buf[ret], "%s ", energy_perf_strings[i++]);
> +
> +	ret += sysfs_emit(&buf[ret], "\n");
> +
> +	return ret;
> +}
> +
> +static ssize_t store_energy_performance_preference(
> +		struct cpufreq_policy *policy, const char *buf, size_t count)
> +{
> +	struct amd_cpudata *cpudata = policy->driver_data;
> +	char str_preference[21];
> +	ssize_t ret;
> +
> +	ret = sscanf(buf, "%20s", str_preference);
> +	if (ret != 1)
> +		return -EINVAL;
> +
> +	ret = match_string(energy_perf_strings, -1, str_preference);
> +	if (ret < 0)
> +		return -EINVAL;
> +
> +	mutex_lock(&amd_pstate_limits_lock);
> +	ret = amd_pstate_set_energy_pref_index(cpudata, ret);
> +	mutex_unlock(&amd_pstate_limits_lock);
> +
> +	return ret ?: count;
> +}
> +
> +static ssize_t show_energy_performance_preference(
> +				struct cpufreq_policy *policy, char *buf)
> +{
> +	struct amd_cpudata *cpudata = policy->driver_data;
> +	int preference;
> +
> +	preference = amd_pstate_get_energy_pref_index(cpudata);
> +	if (preference < 0)
> +		return preference;
> +
> +	return  sysfs_emit(buf, "%s\n", energy_perf_strings[preference]);
> +}
> +
>  cpufreq_freq_attr_ro(amd_pstate_max_freq);
>  cpufreq_freq_attr_ro(amd_pstate_lowest_nonlinear_freq);
>  
>  cpufreq_freq_attr_ro(amd_pstate_highest_perf);
> +cpufreq_freq_attr_rw(energy_performance_preference);
> +cpufreq_freq_attr_ro(energy_performance_available_preferences);
>  
>  static struct freq_attr *amd_pstate_attr[] = {
>  	&amd_pstate_max_freq,
> @@ -603,6 +788,415 @@ static struct freq_attr *amd_pstate_attr[] = {
>  	NULL,
>  };
>  
> +static struct freq_attr *amd_pstate_epp_attr[] = {
> +	&amd_pstate_max_freq,
> +	&amd_pstate_lowest_nonlinear_freq,
> +	&amd_pstate_highest_perf,
> +	&energy_performance_preference,
> +	&energy_performance_available_preferences,
> +	NULL,
> +};
> +
> +static inline void update_boost_state(void)
> +{
> +	u64 misc_en;
> +	struct amd_cpudata *cpudata;
> +
> +	cpudata = all_cpu_data[0];
> +	rdmsrl(MSR_K7_HWCR, misc_en);
> +	global_params.cppc_boost_disabled = misc_en & BIT_ULL(25);
> +}
> +
> +static int amd_pstate_init_cpu(unsigned int cpunum)
> +{
> +	struct amd_cpudata *cpudata;
> +
> +	cpudata = all_cpu_data[cpunum];
> +	if (!cpudata) {
> +		cpudata = kzalloc(sizeof(*cpudata), GFP_KERNEL);
> +		if (!cpudata)
> +			return -ENOMEM;
> +		WRITE_ONCE(all_cpu_data[cpunum], cpudata);
> +
> +		cpudata->cpu = cpunum;
> +	}
> +	cpudata->epp_powersave = -EINVAL;
> +	cpudata->epp_policy = 0;
> +	pr_debug("controlling: cpu %d\n", cpunum);
> +	return 0;
> +}
> +
> +static int __amd_pstate_cpu_init(struct cpufreq_policy *policy)
> +{
> +	int min_freq, max_freq, nominal_freq, lowest_nonlinear_freq, ret;
> +	struct amd_cpudata *cpudata;
> +	struct device *dev;
> +	int rc;
> +	u64 value;
> +
> +	rc = amd_pstate_init_cpu(policy->cpu);
> +	if (rc)
> +		return rc;
> +
> +	cpudata = all_cpu_data[policy->cpu];
> +
> +	dev = get_cpu_device(policy->cpu);
> +	if (!dev)
> +		goto free_cpudata1;
> +
> +	rc = amd_pstate_init_perf(cpudata);
> +	if (rc)
> +		goto free_cpudata1;
> +
> +	min_freq = amd_get_min_freq(cpudata);
> +	max_freq = amd_get_max_freq(cpudata);
> +	nominal_freq = amd_get_nominal_freq(cpudata);
> +	lowest_nonlinear_freq = amd_get_lowest_nonlinear_freq(cpudata);
> +	if (min_freq < 0 || max_freq < 0 || min_freq > max_freq) {
> +		dev_err(dev, "min_freq(%d) or max_freq(%d) value is incorrect\n",
> +				min_freq, max_freq);
> +		ret = -EINVAL;
> +		goto free_cpudata1;
> +	}
> +
> +	policy->min = min_freq;
> +	policy->max = max_freq;
> +
> +	policy->cpuinfo.min_freq = min_freq;
> +	policy->cpuinfo.max_freq = max_freq;
> +	/* It will be updated by governor */
> +	policy->cur = policy->cpuinfo.min_freq;
> +
> +	/* Initial processor data capability frequencies */
> +	cpudata->max_freq = max_freq;
> +	cpudata->min_freq = min_freq;
> +	cpudata->nominal_freq = nominal_freq;
> +	cpudata->lowest_nonlinear_freq = lowest_nonlinear_freq;
> +
> +	policy->driver_data = cpudata;
> +
> +	update_boost_state();
> +	cpudata->epp_cached = amd_pstate_get_epp(cpudata, value);
> +
> +	policy->min = policy->cpuinfo.min_freq;
> +	policy->max = policy->cpuinfo.max_freq;
> +
> +	if (boot_cpu_has(X86_FEATURE_CPPC))
> +		policy->fast_switch_possible = true;
> +
> +	if (!shared_mem && boot_cpu_has(X86_FEATURE_CPPC)) {

Here `shared_mem` is used but it is always 0, as it is not overwritten anywhere.
Do we need `shared_mem` variable at all, can we use only X86_FEATURE_CPPC here?

> +		ret = rdmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, &value);
> +		if (ret)
> +			return ret;
> +		WRITE_ONCE(cpudata->cppc_req_cached, value);
> +
> +		ret = rdmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_CAP1, &value);
> +		if (ret)
> +			return ret;
> +		WRITE_ONCE(cpudata->cppc_cap1_cached, value);
> +	}
> +	amd_pstate_boost_init(cpudata);
> +
> +	return 0;
> +
> +free_cpudata1:
> +	kfree(cpudata);
> +	return ret;
> +}
> +
> +static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
> +{
> +	int ret;
> +
> +	ret = __amd_pstate_cpu_init(policy);
> +	if (ret)
> +		return ret;
> +	/*
> +	 * Set the policy to powersave to provide a valid fallback value in case
> +	 * the default cpufreq governor is neither powersave nor performance.
> +	 */
> +	policy->policy = CPUFREQ_POLICY_POWERSAVE;
> +
> +	return 0;
> +}
> +
> +static int amd_pstate_epp_cpu_exit(struct cpufreq_policy *policy)
> +{
> +	pr_debug("CPU %d exiting\n", policy->cpu);
> +	policy->fast_switch_possible = false;
> +	return 0;
> +}
> +
> +static void amd_pstate_update_max_freq(unsigned int cpu)
> +{
> +	struct cpufreq_policy *policy = policy = cpufreq_cpu_get(cpu);
> +
> +	if (!policy)
> +		return;
> +
> +	refresh_frequency_limits(policy);
> +	cpufreq_cpu_put(policy);
> +}
> +
> +static void amd_pstate_epp_update_limits(unsigned int cpu)
> +{
> +	mutex_lock(&amd_pstate_driver_lock);
> +	update_boost_state();
> +	if (global_params.cppc_boost_disabled) {
> +		for_each_possible_cpu(cpu)
> +			amd_pstate_update_max_freq(cpu);
> +	} else {
> +		cpufreq_update_policy(cpu);
> +	}
> +	mutex_unlock(&amd_pstate_driver_lock);
> +}
> +
> +static int cppc_boost_hold_time_ns = 3 * NSEC_PER_MSEC;
> +
> +static inline void amd_pstate_boost_up(struct amd_cpudata *cpudata)
> +{
> +	u64 hwp_req = READ_ONCE(cpudata->cppc_req_cached);
> +	u64 hwp_cap = READ_ONCE(cpudata->cppc_cap1_cached);
> +	u32 max_limit = (hwp_req & 0xff);
> +	u32 min_limit = (hwp_req & 0xff00) >> 8;
> +	u32 boost_level1;
> +
> +	/* If max and min are equal or already at max, nothing to boost */
> +	if (max_limit == min_limit)
> +		return;
> +
> +	/* Set boost max and min to initial value */
> +	if (!cpudata->cppc_boost_min)
> +		cpudata->cppc_boost_min = min_limit;
> +
> +	boost_level1 = ((AMD_CPPC_NOMINAL_PERF(hwp_cap) + min_limit) >> 1);
> +
> +	if (cpudata->cppc_boost_min < boost_level1)
> +		cpudata->cppc_boost_min = boost_level1;
> +	else if (cpudata->cppc_boost_min < AMD_CPPC_NOMINAL_PERF(hwp_cap))
> +		cpudata->cppc_boost_min = AMD_CPPC_NOMINAL_PERF(hwp_cap);
> +	else if (cpudata->cppc_boost_min == AMD_CPPC_NOMINAL_PERF(hwp_cap))
> +		cpudata->cppc_boost_min = max_limit;
> +	else
> +		return;
> +
> +	hwp_req &= ~AMD_CPPC_MIN_PERF(~0L);
> +	hwp_req |= AMD_CPPC_MIN_PERF(cpudata->cppc_boost_min);
> +	wrmsrl_safe_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, hwp_req);
> +	cpudata->last_update = cpudata->sample.time;
> +}
> +
> +static inline void amd_pstate_boost_down(struct amd_cpudata *cpudata)
> +{
> +	bool expired;
> +
> +	if (cpudata->cppc_boost_min) {
> +		expired = time_after64(cpudata->sample.time, cpudata->last_update +
> +					cppc_boost_hold_time_ns);
> +
> +		if (expired) {
> +			wrmsrl_safe_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ,
> +						cpudata->cppc_req_cached);
> +			cpudata->cppc_boost_min = 0;
> +		}
> +	}
> +
> +	cpudata->last_update = cpudata->sample.time;
> +}
> +
> +static inline void amd_pstate_boost_update_util(struct amd_cpudata *cpudata,
> +						      u64 time)
> +{
> +	cpudata->sample.time = time;
> +	if (smp_processor_id() != cpudata->cpu)
> +		return;
> +
> +	if (cpudata->sched_flags & SCHED_CPUFREQ_IOWAIT) {
> +		bool do_io = false;
> +
> +		cpudata->sched_flags = 0;
> +		/*
> +		 * Set iowait_boost flag and update time. Since IO WAIT flag
> +		 * is set all the time, we can't just conclude that there is
> +		 * some IO bound activity is scheduled on this CPU with just
> +		 * one occurrence. If we receive at least two in two
> +		 * consecutive ticks, then we treat as boost candidate.
> +		 * This is leveraged from Intel Pstate driver.
> +		 */
> +		if (time_before64(time, cpudata->last_io_update + 2 * TICK_NSEC))
> +			do_io = true;
> +
> +		cpudata->last_io_update = time;
> +
> +		if (do_io)
> +			amd_pstate_boost_up(cpudata);
> +
> +	} else {
> +		amd_pstate_boost_down(cpudata);
> +	}
> +}
> +
> +static inline void amd_pstate_cppc_update_hook(struct update_util_data *data,
> +						u64 time, unsigned int flags)
> +{
> +	struct amd_cpudata *cpudata = container_of(data,
> +				struct amd_cpudata, update_util);
> +
> +	cpudata->sched_flags |= flags;
> +
> +	if (smp_processor_id() == cpudata->cpu)
> +		amd_pstate_boost_update_util(cpudata, time);
> +}
> +
> +static void amd_pstate_clear_update_util_hook(unsigned int cpu)
> +{
> +	struct amd_cpudata *cpudata = all_cpu_data[cpu];
> +
> +	if (!cpudata->update_util_set)
> +		return;
> +
> +	cpufreq_remove_update_util_hook(cpu);
> +	cpudata->update_util_set = false;
> +	synchronize_rcu();
> +}
> +
> +static void amd_pstate_set_update_util_hook(unsigned int cpu_num)
> +{
> +	struct amd_cpudata *cpudata = all_cpu_data[cpu_num];
> +
> +	if (!cppc_boost) {
> +		if (cpudata->update_util_set)
> +			amd_pstate_clear_update_util_hook(cpudata->cpu);
> +		return;
> +	}
> +
> +	if (cpudata->update_util_set)
> +		return;
> +
> +	cpudata->sample.time = 0;
> +	cpufreq_add_update_util_hook(cpu_num, &cpudata->update_util,
> +						amd_pstate_cppc_update_hook);
> +	cpudata->update_util_set = true;
> +}
> +
> +static void amd_pstate_epp_init(unsigned int cpu)
> +{
> +	struct amd_cpudata *cpudata = all_cpu_data[cpu];
> +	u32 max_perf, min_perf;
> +	u64 value;
> +	s16 epp;
> +	int ret;
> +
> +	max_perf = READ_ONCE(cpudata->highest_perf);
> +	min_perf = READ_ONCE(cpudata->lowest_perf);
> +
> +	value = READ_ONCE(cpudata->cppc_req_cached);
> +
> +	if (cpudata->policy == CPUFREQ_POLICY_PERFORMANCE)
> +		min_perf = max_perf;
> +
> +	/* Initial min/max values for CPPC Performance Controls Register */
> +	value &= ~AMD_CPPC_MIN_PERF(~0L);
> +	value |= AMD_CPPC_MIN_PERF(min_perf);
> +
> +	value &= ~AMD_CPPC_MAX_PERF(~0L);
> +	value |= AMD_CPPC_MAX_PERF(max_perf);
> +
> +	/* CPPC EPP feature require to set zero to the desire perf bit */
> +	value &= ~AMD_CPPC_DES_PERF(~0L);
> +	value |= AMD_CPPC_DES_PERF(0);
> +
> +	if (cpudata->epp_policy == cpudata->policy)
> +		goto skip_epp;
> +
> +	cpudata->epp_policy = cpudata->policy;
> +
> +	if (cpudata->policy == CPUFREQ_POLICY_PERFORMANCE) {
> +		epp = amd_pstate_get_epp(cpudata, value);
> +		cpudata->epp_powersave = epp;
> +		if (epp < 0)
> +			goto skip_epp;
> +		/* force the epp value to be zero for performance policy */
> +		epp = 0;
> +	} else {
> +		if (cpudata->epp_powersave < 0)
> +			goto skip_epp;
> +		/* Get BIOS pre-defined epp value */
> +		epp = amd_pstate_get_epp(cpudata, value);
> +		if (epp)
> +			goto skip_epp;
> +		epp = cpudata->epp_powersave;
> +	}
> +	/* Set initial EPP value */
> +	if (boot_cpu_has(X86_FEATURE_CPPC)) {
> +		value &= ~GENMASK_ULL(31, 24);
> +		value |= (u64)epp << 24;
> +	}
> +
> +skip_epp:
> +	WRITE_ONCE(cpudata->cppc_req_cached, value);
> +	ret = wrmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, value);
> +	if (!ret)
> +		cpudata->epp_cached = epp;
> +}
> +
> +static void amd_pstate_set_max_limits(struct amd_cpudata *cpudata)
> +{
> +	u64 hwp_cap = READ_ONCE(cpudata->cppc_cap1_cached);
> +	u64 hwp_req = READ_ONCE(cpudata->cppc_req_cached);
> +	u32 max_limit = (hwp_cap >> 24) & 0xff;
> +
> +	hwp_req &= ~AMD_CPPC_MIN_PERF(~0L);
> +	hwp_req |= AMD_CPPC_MIN_PERF(max_limit);
> +	wrmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, hwp_req);
> +}
> +
> +static int amd_pstate_epp_set_policy(struct cpufreq_policy *policy)
> +{
> +	struct amd_cpudata *cpudata;
> +
> +	if (!policy->cpuinfo.max_freq)
> +		return -ENODEV;
> +
> +	pr_debug("set_policy: cpuinfo.max %u policy->max %u\n",
> +				policy->cpuinfo.max_freq, policy->max);
> +
> +	cpudata = all_cpu_data[policy->cpu];
> +	cpudata->policy = policy->policy;
> +
> +	if (boot_cpu_has(X86_FEATURE_CPPC)) {
> +		mutex_lock(&amd_pstate_limits_lock);
> +
> +		if (cpudata->policy == CPUFREQ_POLICY_PERFORMANCE) {
> +			amd_pstate_clear_update_util_hook(policy->cpu);
> +			amd_pstate_set_max_limits(cpudata);
> +		} else {
> +			amd_pstate_set_update_util_hook(policy->cpu);
> +		}
> +
> +		if (boot_cpu_has(X86_FEATURE_CPPC))
> +			amd_pstate_epp_init(policy->cpu);
> +
> +		mutex_unlock(&amd_pstate_limits_lock);
> +	}
> +
> +	return 0;
> +}
> +
> +static void amd_pstate_verify_cpu_policy(struct amd_cpudata *cpudata,
> +					   struct cpufreq_policy_data *policy)
> +{
> +	update_boost_state();
> +	cpufreq_verify_within_cpu_limits(policy);
> +}
> +
> +static int amd_pstate_epp_verify_policy(struct cpufreq_policy_data *policy)
> +{
> +	amd_pstate_verify_cpu_policy(all_cpu_data[policy->cpu], policy);
> +	pr_debug("policy_max =%d, policy_min=%d\n", policy->max, policy->min);
> +	return 0;
> +}
> +
>  static struct cpufreq_driver amd_pstate_driver = {
>  	.flags		= CPUFREQ_CONST_LOOPS | CPUFREQ_NEED_UPDATE_LIMITS,
>  	.verify		= amd_pstate_verify,
> @@ -616,8 +1210,20 @@ static struct cpufreq_driver amd_pstate_driver = {
>  	.attr		= amd_pstate_attr,
>  };
>  
> +static struct cpufreq_driver amd_pstate_epp_driver = {
> +	.flags		= CPUFREQ_CONST_LOOPS,
> +	.verify		= amd_pstate_epp_verify_policy,
> +	.setpolicy	= amd_pstate_epp_set_policy,
> +	.init		= amd_pstate_epp_cpu_init,
> +	.exit		= amd_pstate_epp_cpu_exit,
> +	.update_limits	= amd_pstate_epp_update_limits,
> +	.name		= "amd_pstate_epp",
> +	.attr		= amd_pstate_epp_attr,
> +};
> +
>  static int __init amd_pstate_init(void)
>  {
> +	static struct amd_cpudata **cpudata;
>  	int ret;
>  
>  	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD)
> @@ -641,10 +1247,17 @@ static int __init amd_pstate_init(void)
>  	if (cpufreq_get_current_driver())
>  		return -EEXIST;
>  
> +	if (!epp_off) {
> +		WRITE_ONCE(cppc_active, 1);
> +		if (!default_pstate_driver)
> +			default_pstate_driver = &amd_pstate_epp_driver;
> +	}
> +
>  	/* capability check */
>  	if (boot_cpu_has(X86_FEATURE_CPPC)) {
>  		pr_debug("AMD CPPC MSR based functionality is supported\n");
> -		amd_pstate_driver.adjust_perf = amd_pstate_adjust_perf;
> +		if (!cppc_active)
> +			default_pstate_driver->adjust_perf = amd_pstate_adjust_perf;
>  	} else {
>  		pr_debug("AMD CPPC shared memory based functionality is supported\n");
>  		static_call_update(amd_pstate_enable, cppc_enable);
> @@ -652,6 +1265,10 @@ static int __init amd_pstate_init(void)
>  		static_call_update(amd_pstate_update_perf, cppc_update_perf);
>  	}
>  
> +	cpudata = vzalloc(array_size(sizeof(void *), num_possible_cpus()));
> +	if (!cpudata)
> +		return -ENOMEM;
> +	WRITE_ONCE(all_cpu_data, cpudata);
>  	/* enable amd pstate feature */
>  	ret = amd_pstate_enable(true);
>  	if (ret) {
> @@ -659,9 +1276,9 @@ static int __init amd_pstate_init(void)
>  		return ret;
>  	}
>  
> -	ret = cpufreq_register_driver(&amd_pstate_driver);
> +	ret = cpufreq_register_driver(default_pstate_driver);
>  	if (ret)
> -		pr_err("failed to register amd_pstate_driver with return %d\n",
> +		pr_err("failed to register amd pstate driver with return %d\n",
>  		       ret);
>  
>  	return ret;
> @@ -676,8 +1293,14 @@ static int __init amd_pstate_param(char *str)
>  	if (!strcmp(str, "disable")) {
>  		cppc_load = 0;
>  		pr_info("driver is explicitly disabled\n");
> -	} else if (!strcmp(str, "passive"))
> +	} else if (!strcmp(str, "passive")) {
> +		epp_off = 1;
>  		cppc_load = 1;
> +		default_pstate_driver = &amd_pstate_driver;
> +	} else if (!strcmp(str, "active")) {
> +		cppc_load = 1;
> +		default_pstate_driver = &amd_pstate_epp_driver;
> +	}
>  
>  	return 0;
>  }
> diff --git a/include/linux/amd-pstate.h b/include/linux/amd-pstate.h
> index 1c4b8659f171..7e6e8cab97b3 100644
> --- a/include/linux/amd-pstate.h
> +++ b/include/linux/amd-pstate.h
> @@ -25,6 +25,7 @@ struct amd_aperf_mperf {
>  	u64 aperf;
>  	u64 mperf;
>  	u64 tsc;
> +	u64 time;
>  };
>  
>  /**
> @@ -47,6 +48,18 @@ struct amd_aperf_mperf {
>   * @prev: Last Aperf/Mperf/tsc count value read from register
>   * @freq: current cpu frequency value
>   * @boost_supported: check whether the Processor or SBIOS supports boost mode
> + * @epp_powersave: Last saved CPPC energy performance preference
> +				when policy switched to performance
> + * @epp_policy: Last saved policy used to set energy-performance preference
> + * @epp_cached: Cached CPPC energy-performance preference value
> + * @policy: Cpufreq policy value
> + * @sched_flags: Store scheduler flags for possible cross CPU update
> + * @update_util_set: CPUFreq utility callback is set
> + * @last_update: Time stamp of the last performance state update
> + * @cppc_boost_min: Last CPPC boosted min performance state
> + * @cppc_cap1_cached: Cached value of the last CPPC Capabilities MSR
> + * @update_util: Cpufreq utility callback information
> + * @sample: the stored performance sample
>   *
>   * The amd_cpudata is key private data for each CPU thread in AMD P-State, and
>   * represents all the attributes and goals that AMD P-State requests at runtime.
> @@ -72,6 +85,74 @@ struct amd_cpudata {
>  
>  	u64	freq;
>  	bool	boost_supported;
> +
> +	/* EPP feature related attributes*/
> +	s16	epp_powersave;
> +	s16	epp_policy;
> +	s16	epp_cached;
> +	u32	policy;
> +	u32	sched_flags;
> +	bool	update_util_set;
> +	u64	last_update;
> +	u64	last_io_update;
> +	u32	cppc_boost_min;
> +	u64	cppc_cap1_cached;
> +	struct	update_util_data update_util;
> +	struct	amd_aperf_mperf sample;
> +};
> +
> +/**
> + * struct amd_pstate_params - global parameters for the performance control
> + * @ cppc_boost_disabled wheher the core performance boost disabled
> + */
> +struct amd_pstate_params {
> +	bool cppc_boost_disabled;
> +};
> +
> +#define AMD_CPPC_EPP_PERFORMANCE		0x00
> +#define AMD_CPPC_EPP_BALANCE_PERFORMANCE	0x80
> +#define AMD_CPPC_EPP_BALANCE_POWERSAVE		0xBF
> +#define AMD_CPPC_EPP_POWERSAVE			0xFF
> +
> +/*
> + * AMD Energy Preference Performance (EPP)
> + * The EPP is used in the CCLK DPM controller to drive
> + * the frequency that a core is going to operate during
> + * short periods of activity. EPP values will be utilized for
> + * different OS profiles (balanced, performance, power savings)
> + * display strings corresponding to EPP index in the
> + * energy_perf_strings[]
> + *	index		String
> + *-------------------------------------
> + *	0		default
> + *	1		performance
> + *	2		balance_performance
> + *	3		balance_power
> + *	4		power
> + */
> +enum energy_perf_value_index {
> +	EPP_INDEX_DEFAULT = 0,
> +	EPP_INDEX_PERFORMANCE,
> +	EPP_INDEX_BALANCE_PERFORMANCE,
> +	EPP_INDEX_BALANCE_POWERSAVE,
> +	EPP_INDEX_POWERSAVE,
> +};
> +
> +static const char * const energy_perf_strings[] = {
> +	[EPP_INDEX_DEFAULT] = "default",
> +	[EPP_INDEX_PERFORMANCE] = "performance",
> +	[EPP_INDEX_BALANCE_PERFORMANCE] = "balance_performance",
> +	[EPP_INDEX_BALANCE_POWERSAVE] = "balance_power",
> +	[EPP_INDEX_POWERSAVE] = "power",
> +	NULL
> +};
> +
> +static unsigned int epp_values[] = {
> +	[EPP_INDEX_DEFAULT] = 0,
> +	[EPP_INDEX_PERFORMANCE] = AMD_CPPC_EPP_PERFORMANCE,
> +	[EPP_INDEX_BALANCE_PERFORMANCE] = AMD_CPPC_EPP_BALANCE_PERFORMANCE,
> +	[EPP_INDEX_BALANCE_POWERSAVE] = AMD_CPPC_EPP_BALANCE_POWERSAVE,
> +	[EPP_INDEX_POWERSAVE] = AMD_CPPC_EPP_POWERSAVE,
>  };
>  
>  #endif /* _LINUX_AMD_PSTATE_H */

Thanks & Regards,
Wyes
-- 
Thanks & Regards,
Wyes