RE: [PATCH v9 09/13] cpufreq: amd-pstate: add driver working mode switch support

["Yuan, Perry" <Perry.Yuan@amd.com>]

[AMD Official Use Only - General]



> -----Original Message-----
> From: Karny, Wyes <Wyes.Karny@amd.com>
> Sent: Thursday, January 5, 2023 2:02 PM
> To: Yuan, Perry <Perry.Yuan@amd.com>; rafael.j.wysocki@intel.com;
> Limonciello, Mario <Mario.Limonciello@amd.com>; Huang, Ray
> <Ray.Huang@amd.com>; viresh.kumar@linaro.org
> Cc: Sharma, Deepak <Deepak.Sharma@amd.com>; Fontenot, Nathan
> <Nathan.Fontenot@amd.com>; Deucher, Alexander
> <Alexander.Deucher@amd.com>; Huang, Shimmer
> <Shimmer.Huang@amd.com>; Du, Xiaojian <Xiaojian.Du@amd.com>; Meng,
> Li (Jassmine) <Li.Meng@amd.com>; linux-pm@vger.kernel.org; linux-
> kernel@vger.kernel.org
> Subject: Re: [PATCH v9 09/13] cpufreq: amd-pstate: add driver working mode
> switch support
> 
> Hi Perry,
> 
> On 12/25/2022 10:04 PM, Perry Yuan wrote:
> > From: Perry Yuan <Perry.Yuan@amd.com>
> >
> > While amd-pstate driver was loaded with specific driver mode, it will
> > need to check which mode is enabled for the pstate driver,add this
> > sysfs entry to show the current status
> >
> > $ cat /sys/devices/system/cpu/amd-pstate/status
> > active
> >
> > Meanwhile, user can switch the pstate driver mode with writing mode
> > string to sysfs entry as below.
> >
> > Enable passive mode:
> > $ sudo bash -c "echo passive >  /sys/devices/system/cpu/amd-
> pstate/status"
> >
> > Enable active mode (EPP driver mode):
> > $ sudo bash -c "echo active > /sys/devices/system/cpu/amd-pstate/status"
> >
> > Signed-off-by: Perry Yuan <Perry.Yuan@amd.com>
> > ---
> >  drivers/cpufreq/amd-pstate.c | 118
> > +++++++++++++++++++++++++++++++++++
> >  1 file changed, 118 insertions(+)
> >
> > diff --git a/drivers/cpufreq/amd-pstate.c
> > b/drivers/cpufreq/amd-pstate.c index e3676d1a85c7..8ceca4524fc1 100644
> > --- a/drivers/cpufreq/amd-pstate.c
> > +++ b/drivers/cpufreq/amd-pstate.c
> > @@ -63,6 +63,7 @@ static struct cpufreq_driver *default_pstate_driver;
> > static struct cpufreq_driver amd_pstate_driver;  static struct
> > cpufreq_driver amd_pstate_epp_driver;  static int cppc_state =
> > AMD_PSTATE_DISABLE;
> > +struct kobject *amd_pstate_kobj;
> >
> >  static inline int get_mode_idx_from_str(const char *str, size_t size)
> > { @@ -632,6 +633,8 @@ static int amd_pstate_cpu_init(struct
> > cpufreq_policy *policy)
> >  	policy->driver_data = cpudata;
> >
> >  	amd_pstate_boost_init(cpudata);
> > +	if (!default_pstate_driver->adjust_perf)
> > +		default_pstate_driver->adjust_perf =
> amd_pstate_adjust_perf;
> >
> >  	return 0;
> >
> > @@ -772,12 +775,99 @@ static ssize_t
> show_energy_performance_preference(
> >  	return sysfs_emit(buf, "%s\n", energy_perf_strings[preference]);  }
> >
> > +static ssize_t amd_pstate_show_status(char *buf) {
> > +	if (!default_pstate_driver)
> > +		return sysfs_emit(buf, "off\n");
> 
> IMO 'disable' is more consistent to cppc_state.

Will change the string to be "disable" in v10. 

> 
> > +
> > +	return sysfs_emit(buf, "%s\n",
> amd_pstate_mode_string[cppc_state]);
> > +}
> > +
> > +static void amd_pstate_driver_cleanup(void) {
> > +	default_pstate_driver = NULL;
> > +}
> > +
> > +static int amd_pstate_update_status(const char *buf, size_t size) {
> > +	int ret;
> > +	int mode_idx;
> > +
> > +	if (size > 7 || size < 3)
> > +		return -EINVAL;
> > +	mode_idx = get_mode_idx_from_str(buf, size);
> > +
> > +	switch(mode_idx) {
> > +	case AMD_PSTATE_DISABLE:
> > +		if (!default_pstate_driver)
> > +			return -EINVAL;
> > +		if (cppc_state == AMD_PSTATE_ACTIVE)
> > +			return -EBUSY;
> > +		ret = cpufreq_unregister_driver(default_pstate_driver);
> > +		amd_pstate_driver_cleanup();
> > +		break;
> > +	case AMD_PSTATE_PASSIVE:
> > +		if (default_pstate_driver) {
> > +			if (default_pstate_driver == &amd_pstate_driver)
> > +				return 0;
> > +			cpufreq_unregister_driver(default_pstate_driver);
> > +			cppc_state = AMD_PSTATE_PASSIVE;
> > +			default_pstate_driver = &amd_pstate_driver;
> > +		}
> > +
> > +		ret = cpufreq_register_driver(default_pstate_driver);
> > +		break;
> > +	case AMD_PSTATE_ACTIVE:
> > +		if (default_pstate_driver) {
> > +			if (default_pstate_driver ==
> &amd_pstate_epp_driver)
> > +				return 0;
> > +			cpufreq_unregister_driver(default_pstate_driver);
> > +			default_pstate_driver = &amd_pstate_epp_driver;
> > +			cppc_state = AMD_PSTATE_ACTIVE;
> > +		}
> > +
> > +		ret = cpufreq_register_driver(default_pstate_driver);
> > +		break;
> > +	default:
> > +		break;
> > +		ret = -EINVAL;
> > +	}
> > +
> > +	return ret;
> > +}
> 
> The implementation of amd_pstate_update_status function is good as long
> as the possible states are less.
> Currently prev_state and next_state has 9 combinations. But with guided
> mode this becomes 16 combinations.
> Do you have any concerns if I optimize this function by creating a state
> transition table in guided patch series?

No concern , please go ahead  in your series.

> 
> > +
> > +static ssize_t show_status(struct kobject *kobj,
> > +			   struct kobj_attribute *attr, char *buf) {
> > +	ssize_t ret;
> > +
> > +	mutex_lock(&amd_pstate_driver_lock);
> > +	ret = amd_pstate_show_status(buf);
> > +	mutex_unlock(&amd_pstate_driver_lock);
> > +
> > +	return ret;
> > +}
> > +
> > +static ssize_t store_status(struct kobject *a, struct kobj_attribute *b,
> > +			    const char *buf, size_t count) {
> > +	char *p = memchr(buf, '\n', count);
> > +	int ret;
> > +
> > +	mutex_lock(&amd_pstate_driver_lock);
> > +	ret = amd_pstate_update_status(buf, p ? p - buf : count);
> > +	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);
> >
> >  cpufreq_freq_attr_ro(amd_pstate_highest_perf);
> >  cpufreq_freq_attr_rw(energy_performance_preference);
> >  cpufreq_freq_attr_ro(energy_performance_available_preferences);
> > +define_one_global_rw(status);
> >
> >  static struct freq_attr *amd_pstate_attr[] = {
> >  	&amd_pstate_max_freq,
> > @@ -795,6 +885,15 @@ static struct freq_attr *amd_pstate_epp_attr[] = {
> >  	NULL,
> >  };
> >
> > +static struct attribute *pstate_global_attributes[] = {
> > +	&status.attr,
> > +	NULL
> > +};
> > +
> > +static const struct attribute_group amd_pstate_global_attr_group = {
> > +	.attrs = pstate_global_attributes,
> > +};
> > +
> >  static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)  {
> >  	int min_freq, max_freq, nominal_freq, lowest_nonlinear_freq, ret;
> @@
> > -1154,6 +1253,25 @@ static int __init amd_pstate_init(void)
> >  	if (ret)
> >  		pr_err("failed to register with return %d\n", ret);
> >
> > +	amd_pstate_kobj = kobject_create_and_add("amd-pstate",
> &cpu_subsys.dev_root->kobj);
> > +	if (!amd_pstate_kobj) {
> > +		ret = -EINVAL;
> > +		pr_err("global sysfs registration failed.\n");
> > +		goto kobject_free;
> > +	}
> > +
> > +	ret = sysfs_create_group(amd_pstate_kobj,
> &amd_pstate_global_attr_group);
> > +	if (ret) {
> > +		pr_err("sysfs attribute export failed with error %d.\n", ret);
> > +		goto global_attr_free;
> > +	}
> > +
> > +	return ret;
> > +
> > +global_attr_free:
> > +	kobject_put(amd_pstate_kobj);
> > +kobject_free:
> > +	cpufreq_unregister_driver(default_pstate_driver);
> >  	return ret;
> >  }
> >  device_initcall(amd_pstate_init);
> 
> --
> Thanks & Regards,
> Wyes