hwmon: (pwm-fan) Add support for using PWM FAN as a cooling device

The PWM FAN device can now be used as a thermal cooling device.
Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
Acked-by: Eduardo Valentin <edubezval@gmail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/pwm-fan.c

@@ -24,6 +24,7 @@
 #include <linux/platform_device.h>
 #include <linux/pwm.h>
 #include <linux/sysfs.h>
+#include <linux/thermal.h>
 
 #define MAX_PWM 255
 
@@ -34,6 +35,7 @@ struct pwm_fan_ctx {
 	unsigned int pwm_fan_state;
 	unsigned int pwm_fan_max_state;
 	unsigned int *pwm_fan_cooling_levels;
+	struct thermal_cooling_device *cdev;
 };
 
 static int  __set_pwm(struct pwm_fan_ctx *ctx, unsigned long pwm)
@@ -68,6 +70,17 @@ static int  __set_pwm(struct pwm_fan_ctx *ctx, unsigned long pwm)
 	return ret;
 }
 
+static void pwm_fan_update_state(struct pwm_fan_ctx *ctx, unsigned long pwm)
+{
+	int i;
+
+	for (i = 0; i < ctx->pwm_fan_max_state; ++i)
+		if (pwm < ctx->pwm_fan_cooling_levels[i + 1])
+			break;
+
+	ctx->pwm_fan_state = i;
+}
+
 static ssize_t set_pwm(struct device *dev, struct device_attribute *attr,
 		       const char *buf, size_t count)
 {
@@ -82,6 +95,7 @@ static ssize_t set_pwm(struct device *dev, struct device_attribute *attr,
 	if (ret)
 		return ret;
 
+	pwm_fan_update_state(ctx, pwm);
 	return count;
 }
 
@@ -103,6 +117,62 @@ static struct attribute *pwm_fan_attrs[] = {
 
 ATTRIBUTE_GROUPS(pwm_fan);
 
+/* thermal cooling device callbacks */
+static int pwm_fan_get_max_state(struct thermal_cooling_device *cdev,
+				 unsigned long *state)
+{
+	struct pwm_fan_ctx *ctx = cdev->devdata;
+
+	if (!ctx)
+		return -EINVAL;
+
+	*state = ctx->pwm_fan_max_state;
+
+	return 0;
+}
+
+static int pwm_fan_get_cur_state(struct thermal_cooling_device *cdev,
+				 unsigned long *state)
+{
+	struct pwm_fan_ctx *ctx = cdev->devdata;
+
+	if (!ctx)
+		return -EINVAL;
+
+	*state = ctx->pwm_fan_state;
+
+	return 0;
+}
+
+static int
+pwm_fan_set_cur_state(struct thermal_cooling_device *cdev, unsigned long state)
+{
+	struct pwm_fan_ctx *ctx = cdev->devdata;
+	int ret;
+
+	if (!ctx || (state > ctx->pwm_fan_max_state))
+		return -EINVAL;
+
+	if (state == ctx->pwm_fan_state)
+		return 0;
+
+	ret = __set_pwm(ctx, ctx->pwm_fan_cooling_levels[state]);
+	if (ret) {
+		dev_err(&cdev->device, "Cannot set pwm!\n");
+		return ret;
+	}
+
+	ctx->pwm_fan_state = state;
+
+	return ret;
+}
+
+static const struct thermal_cooling_device_ops pwm_fan_cooling_ops = {
+	.get_max_state = pwm_fan_get_max_state,
+	.get_cur_state = pwm_fan_get_cur_state,
+	.set_cur_state = pwm_fan_set_cur_state,
+};
+
 int pwm_fan_of_get_cooling_data(struct device *dev, struct pwm_fan_ctx *ctx)
 {
 	struct device_node *np = dev->of_node;
@@ -145,8 +215,9 @@ int pwm_fan_of_get_cooling_data(struct device *dev, struct pwm_fan_ctx *ctx)
 
 static int pwm_fan_probe(struct platform_device *pdev)
 {
-	struct device *hwmon;
+	struct thermal_cooling_device *cdev;
 	struct pwm_fan_ctx *ctx;
+	struct device *hwmon;
 	int duty_cycle;
 	int ret;
 
@@ -193,6 +264,21 @@ static int pwm_fan_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	ctx->pwm_fan_state = ctx->pwm_fan_max_state;
+	if (IS_ENABLED(CONFIG_THERMAL)) {
+		cdev = thermal_of_cooling_device_register(pdev->dev.of_node,
+							  "pwm-fan", ctx,
+							  &pwm_fan_cooling_ops);
+		if (IS_ERR(cdev)) {
+			dev_err(&pdev->dev,
+				"Failed to register pwm-fan as cooling device");
+			pwm_disable(ctx->pwm);
+			return PTR_ERR(cdev);
+		}
+		ctx->cdev = cdev;
+		thermal_cdev_update(cdev);
+	}
+
 	return 0;
 }
 
@@ -200,6 +286,7 @@ static int pwm_fan_remove(struct platform_device *pdev)
 {
 	struct pwm_fan_ctx *ctx = platform_get_drvdata(pdev);
 
+	thermal_cooling_device_unregister(ctx->cdev);
 	if (ctx->pwm_value)
 		pwm_disable(ctx->pwm);
 	return 0;