[PATCH 3/4] hwmon: (adt7470) Add thermal cooling device support

[Luiz Angelo Daros de Luca <luizluca@gmail.com>]

The ADT7470 has four PWM outputs that can be used to control fans.
Register each PWM output as an optional thermal cooling device via
Device Tree so it can be referenced by thermal zones.

When the thermal subsystem sets a cooling state, the driver switches
the corresponding PWM channel to manual mode so that the requested duty
cycle takes effect.

Registration is optional: when the "#cooling-cells" property is absent,
devm_thermal_of_child_cooling_device_register() returns -ENODEV and the
driver silently skips that PWM channel.

The PWM cache is populated with an explicit adt7470_update_sensors()
call before the cooling devices are registered, so that an early
get_cur_state() call from the thermal core does not observe stale
(zeroed) values.

Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>
---
 drivers/hwmon/adt7470.c | 122 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 122 insertions(+)

diff --git a/drivers/hwmon/adt7470.c b/drivers/hwmon/adt7470.c
index 4ac292cd7f47..b865f4bd50f8 100644
--- a/drivers/hwmon/adt7470.c
+++ b/drivers/hwmon/adt7470.c
@@ -22,6 +22,7 @@
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/util_macros.h>
+#include <linux/thermal.h>
 
 /* Addresses to scan */
 static const unsigned short normal_i2c[] = { 0x2C, 0x2E, 0x2F, I2C_CLIENT_END };
@@ -142,6 +143,13 @@ static const unsigned short normal_i2c[] = { 0x2C, 0x2E, 0x2F, I2C_CLIENT_END };
 #define ADT7470_FREQ_MASK	0x70
 #define ADT7470_FREQ_SHIFT	4
 
+struct adt7470_data;
+
+struct adt7470_cooling_device {
+	struct adt7470_data *data;
+	int pwm_index;
+};
+
 struct adt7470_data {
 	struct regmap		*regmap;
 	struct mutex		lock;
@@ -171,6 +179,8 @@ struct adt7470_data {
 
 	struct task_struct	*auto_update;
 	unsigned int		auto_update_interval;
+
+	struct adt7470_cooling_device cooling_devices[ADT7470_PWM_COUNT];
 };
 
 /*
@@ -846,6 +856,107 @@ static int adt7470_pwm_write(struct device *dev, u32 attr, int channel, long val
 	return err;
 }
 
+static int adt7470_get_max_state(struct thermal_cooling_device *cdev,
+				 unsigned long *state)
+{
+	*state = ADT7470_PWM_MAX;
+	return 0;
+}
+
+static int adt7470_get_cur_state(struct thermal_cooling_device *cdev,
+				 unsigned long *state)
+{
+	struct adt7470_cooling_device *cooling = cdev->devdata;
+	struct adt7470_data *data = cooling->data;
+
+	mutex_lock(&data->lock);
+	*state = data->pwm[cooling->pwm_index];
+	mutex_unlock(&data->lock);
+
+	return 0;
+}
+
+static int adt7470_set_cur_state(struct thermal_cooling_device *cdev,
+				 unsigned long state)
+{
+	struct adt7470_cooling_device *cooling = cdev->devdata;
+	struct adt7470_data *data = cooling->data;
+	unsigned int pwm_auto_reg_mask;
+	int err;
+
+	if (cooling->pwm_index & 1)
+		pwm_auto_reg_mask = ADT7470_PWM2_AUTO_MASK;
+	else
+		pwm_auto_reg_mask = ADT7470_PWM1_AUTO_MASK;
+
+	state = clamp_val(state, 0, ADT7470_PWM_MAX);
+
+	mutex_lock(&data->lock);
+
+	if (data->pwm[cooling->pwm_index] == state &&
+	    data->pwm_automatic[cooling->pwm_index] == 0) {
+		mutex_unlock(&data->lock);
+		return 0;
+	}
+
+	/* Put the PWM channel in manual mode before updating it. */
+	err = regmap_update_bits(data->regmap,
+				 ADT7470_REG_PWM_CFG(cooling->pwm_index),
+				 pwm_auto_reg_mask, 0);
+	if (err < 0)
+		goto out;
+
+	data->pwm_automatic[cooling->pwm_index] = 0;
+
+	err = regmap_write(data->regmap,
+			   ADT7470_REG_PWM(cooling->pwm_index), state);
+
+	if (err < 0)
+		goto out;
+
+	data->pwm[cooling->pwm_index] = state;
+out:
+	mutex_unlock(&data->lock);
+
+	return err;
+}
+
+static const struct thermal_cooling_device_ops adt7470_cooling_ops = {
+	.get_max_state = adt7470_get_max_state,
+	.get_cur_state = adt7470_get_cur_state,
+	.set_cur_state = adt7470_set_cur_state,
+};
+
+static int adt7470_register_cooling_devices(struct device *dev,
+					    struct adt7470_data *data)
+{
+	int i;
+
+	for (i = 0; i < ADT7470_PWM_COUNT; i++) {
+		struct thermal_cooling_device *cdev;
+		char cdev_name[THERMAL_NAME_LENGTH];
+
+		data->cooling_devices[i].data = data;
+		data->cooling_devices[i].pwm_index = i;
+
+		snprintf(cdev_name, sizeof(cdev_name), "adt7470-pwm%d", i);
+		cdev = devm_thermal_of_child_cooling_device_register(dev,
+								     dev->of_node, cdev_name,
+								     &data->cooling_devices[i],
+								     &adt7470_cooling_ops);
+
+		if (IS_ERR(cdev)) {
+			if (PTR_ERR(cdev) == -ENODEV)
+				continue;
+			return dev_warn_probe(dev, PTR_ERR(cdev),
+					      "failed to register cooling device %s\n",
+					      cdev_name);
+		}
+	}
+
+	return 0;
+}
+
 static ssize_t pwm_max_show(struct device *dev,
 			    struct device_attribute *devattr, char *buf)
 {
@@ -1281,6 +1392,17 @@ static int adt7470_probe(struct i2c_client *client)
 	if (IS_ERR(hwmon_dev))
 		return PTR_ERR(hwmon_dev);
 
+	if (IS_ENABLED(CONFIG_THERMAL)) {
+		/* fill the cache before registering the cooling devices */
+		err = adt7470_update_sensors(data);
+		if (err)
+			return err;
+
+		err = adt7470_register_cooling_devices(dev, data);
+		if (err)
+			return err;
+	}
+
 	data->auto_update = kthread_run(adt7470_update_thread, client, "%s",
 					dev_name(hwmon_dev));
 	if (IS_ERR(data->auto_update))

-- 
2.55.0