hwmon: (adt7475) Add support for pin configuration

The adt7473, adt7475, adt7476 and adt7490 have pins that can be used for
different functions. On the adt7473 and  adt7475 this is pins 5 and 9.
On the adt7476 and adt7490 this is pins 10 and 14.

The first pin can either be PWM2(default) or SMBALERT#. The second pin
can be TACH4(default), THERM#, SMBALERT# or GPIO.

The adt7475 driver has always been able to detect the configuration if
it had been done by an earlier boot stage. Add support for configuring
the pins based on the hardware description in the device tree.
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20220323034056.260455-3-chris.packham@alliedtelesis.co.nzSigned-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/adt7475.c

@@ -112,6 +112,8 @@
 #define CONFIG3_THERM		0x02
 
 #define CONFIG4_PINFUNC		0x03
+#define CONFIG4_THERM		0x01
+#define CONFIG4_SMBALERT	0x02
 #define CONFIG4_MAXDUTY		0x08
 #define CONFIG4_ATTN_IN10	0x30
 #define CONFIG4_ATTN_IN43	0xC0
@@ -1460,6 +1462,96 @@ static int adt7475_update_limits(struct i2c_client *client)
 	return 0;
 }
 
+static int load_config3(const struct i2c_client *client, const char *propname)
+{
+	const char *function;
+	u8 config3;
+	int ret;
+
+	ret = of_property_read_string(client->dev.of_node, propname, &function);
+	if (!ret) {
+		ret = adt7475_read(REG_CONFIG3);
+		if (ret < 0)
+			return ret;
+
+		config3 = ret & ~CONFIG3_SMBALERT;
+		if (!strcmp("pwm2", function))
+			;
+		else if (!strcmp("smbalert#", function))
+			config3 |= CONFIG3_SMBALERT;
+		else
+			return -EINVAL;
+
+		return i2c_smbus_write_byte_data(client, REG_CONFIG3, config3);
+	}
+
+	return 0;
+}
+
+static int load_config4(const struct i2c_client *client, const char *propname)
+{
+	const char *function;
+	u8 config4;
+	int ret;
+
+	ret = of_property_read_string(client->dev.of_node, propname, &function);
+	if (!ret) {
+		ret = adt7475_read(REG_CONFIG4);
+		if (ret < 0)
+			return ret;
+
+		config4 = ret & ~CONFIG4_PINFUNC;
+
+		if (!strcmp("tach4", function))
+			;
+		else if (!strcmp("therm#", function))
+			config4 |= CONFIG4_THERM;
+		else if (!strcmp("smbalert#", function))
+			config4 |= CONFIG4_SMBALERT;
+		else if (!strcmp("gpio", function))
+			config4 |= CONFIG4_PINFUNC;
+		else
+			return -EINVAL;
+
+		return i2c_smbus_write_byte_data(client, REG_CONFIG4, config4);
+	}
+
+	return 0;
+}
+
+static int load_config(const struct i2c_client *client, enum chips chip)
+{
+	int err;
+	const char *prop1, *prop2;
+
+	switch (chip) {
+	case adt7473:
+	case adt7475:
+		prop1 = "adi,pin5-function";
+		prop2 = "adi,pin9-function";
+		break;
+	case adt7476:
+	case adt7490:
+		prop1 = "adi,pin10-function";
+		prop2 = "adi,pin14-function";
+		break;
+	}
+
+	err = load_config3(client, prop1);
+	if (err) {
+		dev_err(&client->dev, "failed to configure %s\n", prop1);
+		return err;
+	}
+
+	err = load_config4(client, prop2);
+	if (err) {
+		dev_err(&client->dev, "failed to configure %s\n", prop2);
+		return err;
+	}
+
+	return 0;
+}
+
 static int set_property_bit(const struct i2c_client *client, char *property,
 			    u8 *config, u8 bit_index)
 {
@@ -1585,6 +1677,10 @@ static int adt7475_probe(struct i2c_client *client)
 		revision = adt7475_read(REG_DEVID2) & 0x07;
 	}
 
+	ret = load_config(client, chip);
+	if (ret)
+		return ret;
+
 	config3 = adt7475_read(REG_CONFIG3);
 	/* Pin PWM2 may alternatively be used for ALERT output */
 	if (!(config3 & CONFIG3_SMBALERT))