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

Wyes Karny
2023-01-05T06:02:25Z

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.

> +
> + 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?

> +
> +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