[PATCH v3 2/2] hwmon: (amc6821) Add PWM polarity configuration with OF

[Francesco Dolcini <francesco@dolcini.it>]

From: Francesco Dolcini <francesco.dolcini@toradex.com>

Add support to configure the PWM-Out pin polarity based on the device
tree. The binding would allow also to configure the PWM period, this is
currently not implemented by the driver.

The driver has a module option to set the PWM polarity (normal=0,
inverted=1), when specified it always takes the precedence over the DT.

Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
---
v3:
 - configure PWM polarity using standard PWM DT properties
v2: https://lore.kernel.org/lkml/20250224180801.128685-3-francesco@dolcini.it/
 - pwminv module parameter takes always the precedence over the DT property
v1: https://lore.kernel.org/all/20250218165633.106867-3-francesco@dolcini.it/
---
 drivers/hwmon/amc6821.c | 50 ++++++++++++++++++++++++++++++++++++-----
 1 file changed, 45 insertions(+), 5 deletions(-)

diff --git a/drivers/hwmon/amc6821.c b/drivers/hwmon/amc6821.c
index 1e3c6acd8974..9ad4e9b63138 100644
--- a/drivers/hwmon/amc6821.c
+++ b/drivers/hwmon/amc6821.c
@@ -23,9 +23,12 @@
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/of_platform.h>
+#include <linux/pwm.h>
 #include <linux/regmap.h>
 #include <linux/slab.h>
 
+#include <dt-bindings/pwm/pwm.h>
+
 /*
  * Addresses to scan.
  */
@@ -37,7 +40,7 @@ static const unsigned short normal_i2c[] = {0x18, 0x19, 0x1a, 0x2c, 0x2d, 0x2e,
  * Insmod parameters
  */
 
-static int pwminv;	/*Inverted PWM output. */
+static int pwminv = -1; /*Inverted PWM output. */
 module_param(pwminv, int, 0444);
 
 static int init = 1; /*Power-on initialization.*/
@@ -845,9 +848,43 @@ static int amc6821_detect(struct i2c_client *client, struct i2c_board_info *info
 	return 0;
 }
 
-static int amc6821_init_client(struct amc6821_data *data)
+static enum pwm_polarity amc6821_pwm_polarity(struct i2c_client *client)
+{
+	enum pwm_polarity polarity = PWM_POLARITY_NORMAL;
+	struct of_phandle_args args;
+	struct device_node *fan_np;
+
+	/*
+	 * For backward compatibility, the pwminv module parameter takes
+	 * always the precedence over any other device description
+	 */
+	if (pwminv == 0)
+		return PWM_POLARITY_NORMAL;
+	if (pwminv > 0)
+		return PWM_POLARITY_INVERSED;
+
+	fan_np = of_get_child_by_name(client->dev.of_node, "fan");
+	if (!fan_np)
+		return PWM_POLARITY_NORMAL;
+
+	if (of_parse_phandle_with_args(fan_np, "pwms", "#pwm-cells", 0, &args))
+		goto out;
+	of_node_put(args.np);
+
+	if (args.args_count != 3)
+		goto out;
+
+	if (args.args[2] & PWM_POLARITY_INVERTED)
+		polarity = PWM_POLARITY_INVERSED;
+out:
+	of_node_put(fan_np);
+	return polarity;
+}
+
+static int amc6821_init_client(struct i2c_client *client, struct amc6821_data *data)
 {
 	struct regmap *regmap = data->regmap;
+	u32 regval;
 	int err;
 
 	if (init) {
@@ -864,11 +901,14 @@ static int amc6821_init_client(struct amc6821_data *data)
 		if (err)
 			return err;
 
+		regval = AMC6821_CONF1_START;
+		if (amc6821_pwm_polarity(client) == PWM_POLARITY_INVERSED)
+			regval |= AMC6821_CONF1_PWMINV;
+
 		err = regmap_update_bits(regmap, AMC6821_REG_CONF1,
 					 AMC6821_CONF1_THERMOVIE | AMC6821_CONF1_FANIE |
 					 AMC6821_CONF1_START | AMC6821_CONF1_PWMINV,
-					 AMC6821_CONF1_START |
-					 (pwminv ? AMC6821_CONF1_PWMINV : 0));
+					 regval);
 		if (err)
 			return err;
 	}
@@ -916,7 +956,7 @@ static int amc6821_probe(struct i2c_client *client)
 				     "Failed to initialize regmap\n");
 	data->regmap = regmap;
 
-	err = amc6821_init_client(data);
+	err = amc6821_init_client(client, data);
 	if (err)
 		return err;
 
-- 
2.39.5