[PATCH v2 3/3] hwmon: (amc6821) Add cooling device support

[João Paulo Gonçalves]

From: João Paulo Gonçalves <joao.goncalves@xxxxxxxxxxx>

Add support for using the AMC6821 as a cooling device. The AMC6821
registers with the thermal framework only if the `cooling-levels`
property is present in the fan device tree child node. Existing behavior
is unchanged, so the AMC6821 can still be used without the thermal
framework (hwmon only).

Signed-off-by: João Paulo Gonçalves <joao.goncalves@xxxxxxxxxxx>
---
v2: Unchanged
v1: https://lore.kernel.org/lkml/20250530-b4-v1-amc6821-cooling-device-support-b4-v1-0-7bb98496c969@xxxxxxxxxxx/
---
 drivers/hwmon/amc6821.c | 97 ++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 92 insertions(+), 5 deletions(-)

diff --git a/drivers/hwmon/amc6821.c b/drivers/hwmon/amc6821.c
index 850a42510649279fba23ed504826384e1d8e335c..218efa0d405b87e838874c273cff7f2872a02448 100644
--- a/drivers/hwmon/amc6821.c
+++ b/drivers/hwmon/amc6821.c
@@ -26,6 +26,7 @@
 #include <linux/pwm.h>
 #include <linux/regmap.h>
 #include <linux/slab.h>
+#include <linux/thermal.h>
 
 #include <dt-bindings/pwm/pwm.h>
 
@@ -126,6 +127,9 @@ module_param(init, int, 0444);
 struct amc6821_data {
 	struct regmap *regmap;
 	struct mutex update_lock;
+	unsigned long fan_state;
+	unsigned long fan_max_state;
+	unsigned int *fan_cooling_levels;
 	enum pwm_polarity pwm_polarity;
 };
 
@@ -805,6 +809,56 @@ static const struct hwmon_chip_info amc6821_chip_info = {
 	.info = amc6821_info,
 };
 
+static int amc6821_get_max_state(struct thermal_cooling_device *cdev, unsigned long *state)
+{
+	struct amc6821_data *data = cdev->devdata;
+
+	if (!data)
+		return -EINVAL;
+
+	*state = data->fan_max_state;
+
+	return 0;
+}
+
+static int amc6821_get_cur_state(struct thermal_cooling_device *cdev, unsigned long *state)
+{
+	struct amc6821_data *data = cdev->devdata;
+
+	if (!data)
+		return -EINVAL;
+
+	*state = data->fan_state;
+
+	return 0;
+}
+
+static int amc6821_set_cur_state(struct thermal_cooling_device *cdev, unsigned long state)
+{
+	struct amc6821_data *data = cdev->devdata;
+	int ret;
+
+	if (!data || state > data->fan_max_state)
+		return -EINVAL;
+
+	ret = regmap_write(data->regmap, AMC6821_REG_DCY,
+			   data->fan_cooling_levels[state]);
+	if (ret)
+		return ret;
+
+	data->fan_state = state;
+
+	/* Change to manual mode (software DCY) */
+	return regmap_update_bits(data->regmap, AMC6821_REG_CONF1,
+				  AMC6821_CONF1_FDRC0 | AMC6821_CONF1_FDRC1, 0);
+}
+
+static const struct thermal_cooling_device_ops amc6821_cooling_ops = {
+	.get_max_state = amc6821_get_max_state,
+	.get_cur_state = amc6821_get_cur_state,
+	.set_cur_state = amc6821_set_cur_state,
+};
+
 /* Return 0 if detection is successful, -ENODEV otherwise */
 static int amc6821_detect(struct i2c_client *client, struct i2c_board_info *info)
 {
@@ -877,11 +931,29 @@ static enum pwm_polarity amc6821_pwm_polarity(struct i2c_client *client,
 	return polarity;
 }
 
-static void amc6821_of_fan_read_data(struct i2c_client *client,
-				     struct amc6821_data *data,
-				     struct device_node *fan_np)
+static int amc6821_of_fan_read_data(struct i2c_client *client,
+				    struct amc6821_data *data,
+				    struct device_node *fan_np)
 {
+	int num;
+
 	data->pwm_polarity = amc6821_pwm_polarity(client, fan_np);
+
+	num = of_property_count_u32_elems(fan_np, "cooling-levels");
+	if (num <= 0)
+		return 0;
+
+	data->fan_max_state = num - 1;
+
+	data->fan_cooling_levels = devm_kcalloc(&client->dev, num,
+						sizeof(u32),
+						GFP_KERNEL);
+
+	if (!data->fan_cooling_levels)
+		return -ENOMEM;
+
+	return of_property_read_u32_array(fan_np, "cooling-levels",
+					  data->fan_cooling_levels, num);
 }
 
 static int amc6821_init_client(struct i2c_client *client, struct amc6821_data *data)
@@ -962,10 +1034,14 @@ static int amc6821_probe(struct i2c_client *client)
 
 	fan_np = of_get_child_by_name(dev->of_node, "fan");
 	if (fan_np) {
-		amc6821_of_fan_read_data(client, data, fan_np);
+		err = amc6821_of_fan_read_data(client, data, fan_np);
 		of_node_put(fan_np);
 	}
 
+	if (err)
+		return dev_err_probe(dev, err,
+				     "Failed to read fan device tree data\n");
+
 	err = amc6821_init_client(client, data);
 	if (err)
 		return err;
@@ -980,7 +1056,18 @@ static int amc6821_probe(struct i2c_client *client)
 	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
 							 data, &amc6821_chip_info,
 							 amc6821_groups);
-	return PTR_ERR_OR_ZERO(hwmon_dev);
+	if (IS_ERR(hwmon_dev))
+		return dev_err_probe(dev, PTR_ERR(hwmon_dev),
+				     "Failed to initialize hwmon\n");
+
+	if (IS_ENABLED(CONFIG_THERMAL) && fan_np && data->fan_cooling_levels)
+		return PTR_ERR_OR_ZERO(devm_thermal_of_cooling_device_register(dev,
+									       fan_np,
+									       client->name,
+									       data,
+									       &amc6821_cooling_ops));
+
+	return 0;
 }
 
 static const struct i2c_device_id amc6821_id[] = {

-- 
2.43.0