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Date: Thu, 13 Jun 2024 12:55:11 -0500
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From: Mario Limonciello <mario.limonciello@amd.com>
Subject: Re: [PATCH v11 5/9] cpufreq: amd-pstate: implement cpb_boost sysfs
 entry for boost control
To: Perry Yuan <perry.yuan@amd.com>, gautham.shenoy@amd.com,
 Borislav.Petkov@amd.com
Cc: rafael.j.wysocki@intel.com, viresh.kumar@linaro.org,
 Alexander.Deucher@amd.com, Xinmei.Huang@amd.com, Xiaojian.Du@amd.com,
 Li.Meng@amd.com, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org
References: <cover.1718262992.git.perry.yuan@amd.com>
 <35464456ab468f389ff3816829647db77924a6b5.1718262992.git.perry.yuan@amd.com>
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On 6/13/2024 02:25, Perry Yuan wrote:
> From: Perry Yuan <Perry.Yuan@amd.com>
> 
> With this new sysfs entry `cpb_boost`created, user can change CPU boost
> state dynamically under `active`, `guided` and `passive` modes.
> And the highest perf and frequency will also be updated as the boost
> state changing.
> 
> 0): check current boost state
> cat /sys/devices/system/cpu/amd_pstate/cpb_boost
> 
> 1): disable CPU boost
> sudo bash -c "echo 0 > /sys/devices/system/cpu/amd_pstate/cpb_boost"
> 
> 2): enable CPU boost
> sudo bash -c "echo 1 > /sys/devices/system/cpu/amd_pstate/cpb_boost"
> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=217931
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=217618
> Signed-off-by: Perry Yuan <Perry.Yuan@amd.com>
> ---
>   drivers/cpufreq/amd-pstate-ut.c |   2 +-
>   drivers/cpufreq/amd-pstate.c    | 117 +++++++++++++++++++++++++++++++-
>   drivers/cpufreq/amd-pstate.h    |   1 +
>   3 files changed, 118 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cpufreq/amd-pstate-ut.c b/drivers/cpufreq/amd-pstate-ut.c
> index fc275d41d51e..b528f198f4c3 100644
> --- a/drivers/cpufreq/amd-pstate-ut.c
> +++ b/drivers/cpufreq/amd-pstate-ut.c
> @@ -227,7 +227,7 @@ static void amd_pstate_ut_check_freq(u32 index)
>   			goto skip_test;
>   		}
>   
> -		if (cpudata->boost_supported) {
> +		if (amd_pstate_global_params.cpb_boost) {
>   			if ((policy->max == cpudata->max_freq) ||
>   					(policy->max == cpudata->nominal_freq))
>   				amd_pstate_ut_cases[index].result = AMD_PSTATE_UT_RESULT_PASS;
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 9f42524074a9..fe7c9d3562c5 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -104,6 +104,7 @@ static bool amd_pstate_prefcore = true;
>   static struct quirk_entry *quirks;
>   struct amd_pstate_global_params amd_pstate_global_params;
>   EXPORT_SYMBOL_GPL(amd_pstate_global_params);
> +static int amd_pstate_cpu_boost(int cpu, bool state);
>   
>   /*
>    * AMD Energy Preference Performance (EPP)
> @@ -738,6 +739,7 @@ static int amd_pstate_boost_set(struct amd_cpudata *cpudata)
>   	if (amd_pstate_global_params.cpb_supported) {
>   		current_pstate_driver->boost_enabled = true;
>   		WRITE_ONCE(cpudata->boost_supported, true);
> +		WRITE_ONCE(cpudata->boost_state, true);
>   	}
>   
>   	amd_pstate_global_params.cpb_boost = amd_pstate_global_params.cpb_supported;
> @@ -745,6 +747,7 @@ static int amd_pstate_boost_set(struct amd_cpudata *cpudata)
>   
>   exit_err:
>   	WRITE_ONCE(cpudata->boost_supported, false);
> +	WRITE_ONCE(cpudata->boost_state, false);
>   	current_pstate_driver->boost_enabled = false;
>   	amd_pstate_global_params.cpb_boost = false;
>   	return ret;
> @@ -1348,6 +1351,116 @@ static ssize_t prefcore_show(struct device *dev,
>   	return sysfs_emit(buf, "%s\n", str_enabled_disabled(amd_pstate_prefcore));
>   }
>   
> +static int amd_pstate_cpu_boost_update(struct cpufreq_policy *policy, bool on)
> +{
> +	struct amd_cpudata *cpudata = policy->driver_data;
> +	struct cppc_perf_ctrls perf_ctrls;
> +	u32 highest_perf, nominal_perf, nominal_freq, max_freq;
> +	int ret;
> +
> +	if (!policy) {
> +		pr_err("policy is null\n");
> +		return -ENODATA;
> +	}

This is dead code that can't possibly be hit, because there would be a 
NULL pointer dereference above for this line:

	struct amd_cpudata *cpudata = policy->driver_data;

Furthermore, the caller for this function, amd_pstate_cpu_boost() has
the same check already.

So drop the check here.

> +
> +	highest_perf = READ_ONCE(cpudata->highest_perf);
> +	nominal_perf = READ_ONCE(cpudata->nominal_perf);
> +	nominal_freq = READ_ONCE(cpudata->nominal_freq);
> +	max_freq = READ_ONCE(cpudata->max_freq);
> +
> +	if (boot_cpu_has(X86_FEATURE_CPPC)) {
> +		u64 value = READ_ONCE(cpudata->cppc_req_cached);
> +
> +		value &= ~GENMASK_ULL(7, 0);
> +		value |= on ? highest_perf : nominal_perf;
> +		WRITE_ONCE(cpudata->cppc_req_cached, value);
> +
> +		wrmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, value);
> +	} else {
> +		perf_ctrls.max_perf = on ? highest_perf : nominal_perf;
> +		ret = cppc_set_epp_perf(cpudata->cpu, &perf_ctrls, 1);
> +		if (ret) {
> +			cpufreq_cpu_release(policy);
> +			pr_debug("failed to set energy perf value (%d)\n", ret);
> +			return ret;
> +		}
> +	}
> +
> +	if (on)
> +		policy->cpuinfo.max_freq = max_freq;
> +	else
> +		policy->cpuinfo.max_freq = nominal_freq * 1000;
> +
> +	policy->max = policy->cpuinfo.max_freq;
> +
> +	if (cppc_state == AMD_PSTATE_PASSIVE) {
> +		ret = freq_qos_update_request(&cpudata->req[1], policy->cpuinfo.max_freq);
> +		if (ret < 0)
> +			pr_debug("Failed to update freq constraint: CPU%d\n", cpudata->cpu);
> +	}
> +
> +	return ret < 0 ? ret : 0;
> +}
> +
> +static int amd_pstate_cpu_boost(int cpu, bool state)
> +{
> +	int ret;
> +	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
> +	struct amd_cpudata *cpudata = policy->driver_data;
> +
> +	if (!policy) {
> +		pr_err("policy is NULL\n");
> +		ret = -ENODATA;
> +		goto err_exit;
> +	}
> +
> +	ret = amd_pstate_cpu_boost_update(policy, state);
> +	refresh_frequency_limits(policy);
> +	WRITE_ONCE(cpudata->boost_state, state);
> +	policy->boost_enabled = state;
> +
> +err_exit:
> +	cpufreq_cpu_put(policy);
> +	return ret < 0 ? ret : 0;
> +}
> +
> +static ssize_t cpb_boost_show(struct device *dev,
> +			   struct device_attribute *attr, char *buf)
> +{
> +	return sysfs_emit(buf, "%u\n", amd_pstate_global_params.cpb_boost);
> +}
> +
> +static ssize_t cpb_boost_store(struct device *dev, struct device_attribute *b,
> +			    const char *buf, size_t count)
> +{
> +	bool new_state;
> +	ssize_t ret;
> +	int cpu;
> +
> +	if (!amd_pstate_global_params.cpb_supported) {
> +		pr_err("Boost mode is not supported by this processor or SBIOS\n");
> +		return -EINVAL;
> +	}
> +
> +	ret = kstrtobool(buf, &new_state);
> +	if (ret)
> +		return ret;
> +
> +	mutex_lock(&amd_pstate_driver_lock);
> +	for_each_present_cpu(cpu) {
> +		ret = amd_pstate_cpu_boost(cpu, new_state);
> +		if (ret < 0) {
> +			pr_warn("failed to update cpu boost for CPU%d (%zd)\n", cpu, ret);
> +			goto err_exit;
> +		}
> +	}
> +	amd_pstate_global_params.cpb_boost = !!new_state;
> +
> +err_exit:
> +	mutex_unlock(&amd_pstate_driver_lock);
> +	return ret < 0 ? ret : count;
> +}
> +
>   cpufreq_freq_attr_ro(amd_pstate_max_freq);
>   cpufreq_freq_attr_ro(amd_pstate_lowest_nonlinear_freq);
>   
> @@ -1358,6 +1471,7 @@ 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(cpb_boost);
>   
>   static struct freq_attr *amd_pstate_attr[] = {
>   	&amd_pstate_max_freq,
> @@ -1382,6 +1496,7 @@ static struct freq_attr *amd_pstate_epp_attr[] = {
>   static struct attribute *pstate_global_attributes[] = {
>   	&dev_attr_status.attr,
>   	&dev_attr_prefcore.attr,
> +	&dev_attr_cpb_boost.attr,
>   	NULL
>   };
>   
> @@ -1420,7 +1535,7 @@ static int amd_pstate_init_boost(struct cpufreq_policy *policy)
>   	if (ret)
>   		return ret;
>   
> -	policy->boost_enabled = READ_ONCE(cpudata->boost_supported);
> +	policy->boost_enabled = READ_ONCE(cpudata->boost_state);
>   
>   	return 0;
>   }
> diff --git a/drivers/cpufreq/amd-pstate.h b/drivers/cpufreq/amd-pstate.h
> index 0b75a6267fca..9eba854ab7d3 100644
> --- a/drivers/cpufreq/amd-pstate.h
> +++ b/drivers/cpufreq/amd-pstate.h
> @@ -99,6 +99,7 @@ struct amd_cpudata {
>   	u32	policy;
>   	u64	cppc_cap1_cached;
>   	bool	suspended;
> +	bool	boost_state;
>   };
>   
>   /**