[PATCH v2 5/6] cpufreq: amd_pstate: Add guided mode control support via sysfs

[Wyes Karny]

amd_pstate driver's `status` sysfs entry helps to control the driver's
mode dynamically by user. After the addition of guided mode the
combinations of mode transitions have been increased (16 combinations).
Therefore optimise the amd_pstate_update_status function by implementing
a state transition table.

There are 4 states amd_pstate supports, namely: 'disable', 'passive',
'active', and 'guided'.  The transition from any state to any other
state is possible after this change. Only if the state requested matches
with the current state then -EBUSY value is returned.

Sysfs interface:

To disable amd_pstate driver:
 # echo disable > /sys/devices/system/cpu/amd_pstate/status

To enable passive mode:
 # echo passive > /sys/devices/system/cpu/amd_pstate/status

To change mode to active:
 # echo active > /sys/devices/system/cpu/amd_pstate/status

To change mode to guided:
 # echo guided > /sys/devices/system/cpu/amd_pstate/status

Signed-off-by: Wyes Karny <wyes.karny@xxxxxxx>
---
 drivers/cpufreq/amd-pstate.c | 144 ++++++++++++++++++++++++++---------
 1 file changed, 109 insertions(+), 35 deletions(-)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 20d78dad712d..4a2b559fd712 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -65,6 +65,8 @@ static struct cpufreq_driver amd_pstate_epp_driver;
 static int cppc_state = AMD_PSTATE_DISABLE;
 struct kobject *amd_pstate_kobj;
 
+typedef int (*cppc_mode_transition_fn)(int);
+
 static inline int get_mode_idx_from_str(const char *str, size_t size)
 {
 	int i;
@@ -806,55 +808,127 @@ static ssize_t amd_pstate_show_status(char *buf)
 
 static void amd_pstate_driver_cleanup(void)
 {
+	amd_pstate_enable(false);
+	cppc_state = AMD_PSTATE_DISABLE;
 	default_pstate_driver = NULL;
 }
 
-static int amd_pstate_update_status(const char *buf, size_t size)
+static int amd_pstate_register_driver(int mode)
 {
 	int ret;
-	int mode_idx;
 
-	if (size > 7 || size < 3)
+	if (mode == AMD_PSTATE_PASSIVE || mode == AMD_PSTATE_GUIDED)
+		default_pstate_driver = &amd_pstate_driver;
+	else if (mode == AMD_PSTATE_ACTIVE)
+		default_pstate_driver = &amd_pstate_epp_driver;
+	else
 		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);
+	ret = cpufreq_register_driver(default_pstate_driver);
+	if (ret) {
 		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;
-		}
+		return ret;
+	}
 
-		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;
+	cppc_state = mode;
+	return 0;
+}
+
+static int amd_pstate_unregister_driver(int dummy)
+{
+	int ret;
+
+	ret = cpufreq_unregister_driver(default_pstate_driver);
+
+	if (ret)
+		return ret;
+
+	amd_pstate_driver_cleanup();
+	return 0;
+}
+
+static void amd_pstate_change_mode_without_dvr_change(int mode)
+{
+	int cpu = 0;
+
+	cppc_state = mode;
+	if (!boot_cpu_has(X86_FEATURE_CPPC)) {
+		if (cppc_state == AMD_PSTATE_PASSIVE) {
+			for_each_present_cpu(cpu) {
+				cppc_set_auto_sel(cpu, 0);
+			}
+		} else if (cppc_state == AMD_PSTATE_GUIDED) {
+				for_each_present_cpu(cpu) {
+					cppc_set_auto_sel(cpu, 1);
+				}
 		}
+	}
+}
 
-		ret = cpufreq_register_driver(default_pstate_driver);
-		break;
-	default:
-		break;
-		ret = -EINVAL;
+static int amd_pstate_change_driver_mode(int mode)
+{
+	int ret;
+
+	if ((mode == AMD_PSTATE_GUIDED && cppc_state == AMD_PSTATE_PASSIVE) ||
+			(mode == AMD_PSTATE_PASSIVE && cppc_state == AMD_PSTATE_GUIDED)) {
+		amd_pstate_change_mode_without_dvr_change(mode);
+		return 0;
 	}
 
-	return ret;
+	ret = amd_pstate_unregister_driver(0);
+	if (ret)
+		return ret;
+
+	ret = amd_pstate_register_driver(mode);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+/* Mode transition table */
+cppc_mode_transition_fn mode_state_machine[AMD_PSTATE_MAX][AMD_PSTATE_MAX] = {
+	[AMD_PSTATE_DISABLE]         = {
+		[AMD_PSTATE_DISABLE]     = NULL,
+		[AMD_PSTATE_PASSIVE]     = amd_pstate_register_driver,
+		[AMD_PSTATE_ACTIVE]      = amd_pstate_register_driver,
+		[AMD_PSTATE_GUIDED]      = amd_pstate_register_driver,
+	},
+	[AMD_PSTATE_PASSIVE]         = {
+		[AMD_PSTATE_DISABLE]     = amd_pstate_unregister_driver,
+		[AMD_PSTATE_PASSIVE]     = NULL,
+		[AMD_PSTATE_ACTIVE]      = amd_pstate_change_driver_mode,
+		[AMD_PSTATE_GUIDED]      = amd_pstate_change_driver_mode,
+	},
+	[AMD_PSTATE_ACTIVE]          = {
+		[AMD_PSTATE_DISABLE]     = amd_pstate_unregister_driver,
+		[AMD_PSTATE_PASSIVE]     = amd_pstate_change_driver_mode,
+		[AMD_PSTATE_ACTIVE]      = NULL,
+		[AMD_PSTATE_GUIDED]      = amd_pstate_change_driver_mode,
+	},
+	[AMD_PSTATE_GUIDED]          = {
+		[AMD_PSTATE_DISABLE]     = amd_pstate_unregister_driver,
+		[AMD_PSTATE_PASSIVE]     = amd_pstate_change_driver_mode,
+		[AMD_PSTATE_ACTIVE]      = amd_pstate_change_driver_mode,
+		[AMD_PSTATE_GUIDED]      = NULL,
+	},
+};
+
+static int amd_pstate_update_status(const char *buf, size_t size)
+{
+	int mode_idx;
+
+	if (size > 7 || size < 3)
+		return -EINVAL;
+	mode_idx = get_mode_idx_from_str(buf, size);
+
+	if (mode_idx < 0 || mode_idx >= AMD_PSTATE_MAX)
+		return -EINVAL;
+
+	if (mode_state_machine[cppc_state][mode_idx])
+		return mode_state_machine[cppc_state][mode_idx](mode_idx);
+
+	return -EBUSY;
 }
 
 static ssize_t show_status(struct kobject *kobj,
-- 
2.34.1