[PATCH 08/10] platform/x86: alienware-wmi-wmax: Add support for manual fan control

[Kurt Borja <kuurtb@gmail.com>]

All models with the "AWCC" WMAX device support a way of manually
controlling fans.

The PWM duty cycle of a fan can't be controlled directly. Instead the
AWCC interface let's us tune a PWM `boost` value, which has the
following empirically discovered behavior over the PWM value:

	pwm = pwm_base + (pwm_boost / 255) * (pwm_max - pwm_base)

Where the pwm_base is the locked PWM value controlled by the EC and
pwm_boost is a value between 0 and 255.

This pwm_boost knob is exposed as a standard `pwm` attribute.

Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Kurt Borja <kuurtb@gmail.com>
---
 .../platform/x86/dell/alienware-wmi-wmax.c    | 55 +++++++++++++++++--
 1 file changed, 49 insertions(+), 6 deletions(-)

diff --git a/drivers/platform/x86/dell/alienware-wmi-wmax.c b/drivers/platform/x86/dell/alienware-wmi-wmax.c
index 5f02da7ff25f..06d6f88ea54b 100644
--- a/drivers/platform/x86/dell/alienware-wmi-wmax.c
+++ b/drivers/platform/x86/dell/alienware-wmi-wmax.c
@@ -13,6 +13,7 @@
 #include <linux/dmi.h>
 #include <linux/hwmon.h>
 #include <linux/jiffies.h>
+#include <linux/minmax.h>
 #include <linux/moduleparam.h>
 #include <linux/mutex.h>
 #include <linux/overflow.h>
@@ -176,10 +177,12 @@ enum AWCC_THERMAL_INFORMATION_OPERATIONS {
 	AWCC_OP_GET_MIN_RPM			= 0x08,
 	AWCC_OP_GET_MAX_RPM			= 0x09,
 	AWCC_OP_GET_CURRENT_PROFILE		= 0x0B,
+	AWCC_OP_GET_FAN_BOOST			= 0x0C,
 };
 
 enum AWCC_THERMAL_CONTROL_OPERATIONS {
 	AWCC_OP_ACTIVATE_PROFILE		= 0x01,
+	AWCC_OP_SET_FAN_BOOST			= 0x02,
 };
 
 enum AWCC_GAME_SHIFT_STATUS_OPERATIONS {
@@ -563,12 +566,13 @@ static inline int awcc_thermal_information(struct wmi_device *wdev, u8 operation
 	return __awcc_wmi_command(wdev, AWCC_METHOD_THERMAL_INFORMATION, &args, out);
 }
 
-static inline int awcc_thermal_control(struct wmi_device *wdev, u8 profile)
+static inline int awcc_thermal_control(struct wmi_device *wdev, u8 operation,
+				       u8 arg1, u8 arg2)
 {
 	struct wmax_u32_args args = {
-		.operation = AWCC_OP_ACTIVATE_PROFILE,
-		.arg1 = profile,
-		.arg2 = 0,
+		.operation = operation,
+		.arg1 = arg1,
+		.arg2 = arg2,
 		.arg3 = 0,
 	};
 	u32 out;
@@ -684,6 +688,11 @@ static umode_t awcc_hwmon_is_visible(const void *drvdata, enum hwmon_sensor_type
 		if (channel < priv->fan_count)
 			return 0444;
 
+		break;
+	case hwmon_pwm:
+		if (channel < priv->fan_count)
+			return 0644;
+
 		break;
 	default:
 		break;
@@ -698,6 +707,7 @@ static int awcc_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
 	struct awcc_priv *priv = dev_get_drvdata(dev);
 	struct awcc_temp_channel_data *temp;
 	struct awcc_fan_channel_data *fan;
+	u32 fan_boost;
 	int ret;
 
 	switch (type) {
@@ -742,6 +752,16 @@ static int awcc_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
 			return -EOPNOTSUPP;
 		}
 
+		break;
+	case hwmon_pwm:
+		fan = &priv->fan_data[channel];
+
+		ret = awcc_thermal_information(priv->wdev, AWCC_OP_GET_FAN_BOOST,
+					       fan->id, &fan_boost);
+		if (ret)
+			return ret;
+
+		*val = fan_boost;
 		break;
 	default:
 		return -EOPNOTSUPP;
@@ -796,10 +816,27 @@ static int awcc_hwmon_read_string(struct device *dev, enum hwmon_sensor_types ty
 	return 0;
 }
 
+
+static int awcc_hwmon_write(struct device *dev, enum hwmon_sensor_types type,
+			    u32 attr, int channel, long val)
+{
+	struct awcc_priv *priv = dev_get_drvdata(dev);
+	u8 fan_id = priv->fan_data[channel].id;
+
+	switch (type) {
+	case hwmon_pwm:
+		return awcc_thermal_control(priv->wdev, AWCC_OP_SET_FAN_BOOST,
+					    fan_id, (u8)clamp_val(val, 0, 255));
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
 static const struct hwmon_ops awcc_hwmon_ops = {
 	.is_visible = awcc_hwmon_is_visible,
 	.read = awcc_hwmon_read,
 	.read_string = awcc_hwmon_read_string,
+	.write = awcc_hwmon_write,
 };
 
 static const struct hwmon_channel_info * const awcc_hwmon_info[] = {
@@ -814,6 +851,12 @@ static const struct hwmon_channel_info * const awcc_hwmon_info[] = {
 			   HWMON_F_LABEL | HWMON_F_INPUT | HWMON_F_MIN | HWMON_F_MAX,
 			   HWMON_F_LABEL | HWMON_F_INPUT | HWMON_F_MIN | HWMON_F_MAX
 			   ),
+	HWMON_CHANNEL_INFO(pwm,
+			   HWMON_PWM_INPUT,
+			   HWMON_PWM_INPUT,
+			   HWMON_PWM_INPUT,
+			   HWMON_PWM_INPUT
+			   ),
 	NULL
 };
 
@@ -954,8 +997,8 @@ static int awcc_platform_profile_set(struct device *dev,
 		}
 	}
 
-	return awcc_thermal_control(priv->wdev,
-				    priv->supported_profiles[profile]);
+	return awcc_thermal_control(priv->wdev, AWCC_OP_ACTIVATE_PROFILE,
+				    priv->supported_profiles[profile], 0);
 }
 
 static int awcc_platform_profile_probe(void *drvdata, unsigned long *choices)
-- 
2.48.1