[PATCH v8 09/13] cpufreq: amd-pstate: add driver working mode switch support

[Perry Yuan <perry.yuan@amd.com>]

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 | 128 +++++++++++++++++++++++++++++++++++
 1 file changed, 128 insertions(+)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index fc12d35bc7bd..e8996e937e63 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -64,6 +64,7 @@ static struct cpufreq_driver amd_pstate_driver;
 static struct cpufreq_driver amd_pstate_epp_driver;
 static struct amd_cpudata **all_cpu_data;
 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)
 {
@@ -90,6 +91,8 @@ static struct amd_pstate_params global_params;
 static DEFINE_MUTEX(amd_pstate_limits_lock);
 static DEFINE_MUTEX(amd_pstate_driver_lock);
 
+static DEFINE_SPINLOCK(cppc_notify_lock);
+
 static s16 amd_pstate_get_epp(struct amd_cpudata *cpudata, u64 cppc_req_cached)
 {
 	u64 epp;
@@ -644,6 +647,8 @@ 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;
 
@@ -784,12 +789,106 @@ 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", default_pstate_driver == &amd_pstate_epp_driver ?
+					"active" : "passive");
+}
+
+static void amd_pstate_driver_cleanup(void)
+{
+	unsigned int cpu;
+
+	cpus_read_lock();
+	for_each_online_cpu(cpu) {
+		if (all_cpu_data[cpu]) {
+			spin_lock(&cppc_notify_lock);
+			kfree(all_cpu_data[cpu]);
+			WRITE_ONCE(all_cpu_data[cpu], NULL);
+			spin_unlock(&cppc_notify_lock);
+		}
+	}
+	cpus_read_unlock();
+
+	default_pstate_driver = NULL;
+}
+
+static int amd_pstate_update_status(const char *buf, size_t size)
+{
+	if (size == 3 && !strncmp(buf, "off", size)) {
+		if (!default_pstate_driver)
+			return -EINVAL;
+
+		if (cppc_state == AMD_PSTATE_ACTIVE)
+			return -EBUSY;
+
+		cpufreq_unregister_driver(default_pstate_driver);
+		amd_pstate_driver_cleanup();
+		return 0;
+	}
+
+	if (size == 6 && !strncmp(buf, "active", size)) {
+		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;
+		}
+
+		return cpufreq_register_driver(default_pstate_driver);
+	}
+
+	if (size == 7 && !strncmp(buf, "passive", size)) {
+		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;
+		}
+
+		return cpufreq_register_driver(default_pstate_driver);
+	}
+
+	return -EINVAL;
+}
+
+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,
@@ -807,6 +906,15 @@ 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 inline void update_boost_state(void)
 {
 	u64 misc_en;
@@ -1228,6 +1336,26 @@ 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:
+	kfree(cpudata);
+	cpufreq_unregister_driver(default_pstate_driver);
 	return ret;
 }
 device_initcall(amd_pstate_init);
-- 
2.34.1