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    SubjectRe: [PATCH v9 09/13] cpufreq: amd-pstate: add driver working mode switch support
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    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");
    > +
    > + 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;
    > +}
    > +
    > +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);

    IMO amd_pstate would make it more consistent because the boot param is called "amd_pstate".
    But no strong opinion on this.

    > + 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

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