[PATCH v7 09/13] cpufreq: amd-pstate: add driver working mode status sysfs entry

[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 | 101 +++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 4cd53c010215..c90aee3ee42d 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -64,6 +64,8 @@ static bool cppc_active;
 static int cppc_load __initdata;
 
 static struct cpufreq_driver *default_pstate_driver;
+static struct cpufreq_driver amd_pstate_epp_driver;
+static struct cpufreq_driver amd_pstate_driver;
 static struct amd_cpudata **all_cpu_data;
 static struct amd_pstate_params global_params;
 
@@ -72,6 +74,7 @@ static DEFINE_MUTEX(amd_pstate_driver_lock);
 struct kobject *amd_pstate_kobj;
 
 static bool cppc_boost __read_mostly;
+static DEFINE_SPINLOCK(cppc_notify_lock);
 
 static s16 amd_pstate_get_epp(struct amd_cpudata *cpudata, u64 cppc_req_cached)
 {
@@ -629,6 +632,8 @@ 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;
 
@@ -802,6 +807,100 @@ static ssize_t store_cppc_dynamic_boost(struct kobject *a,
 	return count;
 }
 
+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_clear_update_util_hook(unsigned int cpu);
+static void amd_pstate_driver_cleanup(void)
+{
+	unsigned int cpu;
+
+	cpus_read_lock();
+	for_each_online_cpu(cpu) {
+		if (all_cpu_data[cpu]) {
+			if (default_pstate_driver == &amd_pstate_epp_driver)
+				amd_pstate_clear_update_util_hook(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_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;
+		}
+
+		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);
+		}
+		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);
 
@@ -809,6 +908,7 @@ 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(cppc_dynamic_boost);
+define_one_global_rw(status);
 
 static struct freq_attr *amd_pstate_attr[] = {
 	&amd_pstate_max_freq,
@@ -828,6 +928,7 @@ static struct freq_attr *amd_pstate_epp_attr[] = {
 
 static struct attribute *pstate_global_attributes[] = {
 	&cppc_dynamic_boost.attr,
+	&status.attr,
 	NULL
 };
 
-- 
2.34.1