hwmon: (sch5627) Add pwmX_auto_channels_temp support

After doing some research, it seems that Fujitsu's
hardware monitoring solution exports data describing
which temperature sensors affect which fans, similar
to the data in fan_source of the ftsteutates driver.
Writing 0 into these registers forces the fans to
full speed.
Export this data with standard attributes.
Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Link: https://lore.kernel.org/r/20220224061210.16452-3-W_Armin@gmx.deSigned-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/hwmon/sch5627.rst

@@ -20,6 +20,10 @@ Description
 SMSC SCH5627 Super I/O chips include complete hardware monitoring
 capabilities. They can monitor up to 5 voltages, 4 fans and 8 temperatures.
 
+In addition, the SCH5627 exports data describing which temperature sensors
+affect the speed of each fan. Setting pwmX_auto_channels_temp to 0 forces
+the corresponding fan to full speed until another value is written.
+
 The SMSC SCH5627 hardware monitoring part also contains an integrated
 watchdog. In order for this watchdog to function some motherboard specific
 initialization most be done by the BIOS, so if the watchdog is not enabled

drivers/hwmon/sch5627.c

@@ -52,6 +52,9 @@ static const u16 SCH5627_REG_FAN[SCH5627_NO_FANS] = {
 static const u16 SCH5627_REG_FAN_MIN[SCH5627_NO_FANS] = {
 	0x62, 0x64, 0x66, 0x68 };
 
+static const u16 SCH5627_REG_PWM_MAP[SCH5627_NO_FANS] = {
+	0xA0, 0xA1, 0xA2, 0xA3 };
+
 static const u16 SCH5627_REG_IN_MSB[SCH5627_NO_IN] = {
 	0x22, 0x23, 0x24, 0x25, 0x189 };
 static const u16 SCH5627_REG_IN_LSN[SCH5627_NO_IN] = {
@@ -223,6 +226,9 @@ static int reg_to_rpm(u16 reg)
 static umode_t sch5627_is_visible(const void *drvdata, enum hwmon_sensor_types type, u32 attr,
 				  int channel)
 {
+	if (type == hwmon_pwm && attr == hwmon_pwm_auto_channels_temp)
+		return 0644;
+
 	return 0444;
 }
 
@@ -278,6 +284,23 @@ static int sch5627_read(struct device *dev, enum hwmon_sensor_types type, u32 at
 			break;
 		}
 		break;
+	case hwmon_pwm:
+		switch (attr) {
+		case hwmon_pwm_auto_channels_temp:
+			mutex_lock(&data->update_lock);
+			ret = sch56xx_read_virtual_reg(data->addr, SCH5627_REG_PWM_MAP[channel]);
+			mutex_unlock(&data->update_lock);
+
+			if (ret < 0)
+				return ret;
+
+			*val = ret;
+
+			return 0;
+		default:
+			break;
+		}
+		break;
 	case hwmon_in:
 		ret = sch5627_update_in(data);
 		if (ret < 0)
@@ -318,10 +341,42 @@ static int sch5627_read_string(struct device *dev, enum hwmon_sensor_types type,
 	return -EOPNOTSUPP;
 }
 
+static int sch5627_write(struct device *dev, enum hwmon_sensor_types type, u32 attr, int channel,
+			 long val)
+{
+	struct sch5627_data *data = dev_get_drvdata(dev);
+	int ret;
+
+	switch (type) {
+	case hwmon_pwm:
+		switch (attr) {
+		case hwmon_pwm_auto_channels_temp:
+			/* registers are 8 bit wide */
+			if (val > U8_MAX || val < 0)
+				return -EINVAL;
+
+			mutex_lock(&data->update_lock);
+			ret = sch56xx_write_virtual_reg(data->addr, SCH5627_REG_PWM_MAP[channel],
+							val);
+			mutex_unlock(&data->update_lock);
+
+			return ret;
+		default:
+			break;
+		}
+		break;
+	default:
+		break;
+	}
+
+	return -EOPNOTSUPP;
+}
+
 static const struct hwmon_ops sch5627_ops = {
 	.is_visible = sch5627_is_visible,
 	.read = sch5627_read,
 	.read_string = sch5627_read_string,
+	.write = sch5627_write,
 };
 
 static const struct hwmon_channel_info *sch5627_info[] = {
@@ -342,6 +397,12 @@ static const struct hwmon_channel_info *sch5627_info[] = {
 			   HWMON_F_INPUT | HWMON_F_MIN | HWMON_F_FAULT,
 			   HWMON_F_INPUT | HWMON_F_MIN | HWMON_F_FAULT
 			   ),
+	HWMON_CHANNEL_INFO(pwm,
+			   HWMON_PWM_AUTO_CHANNELS_TEMP,
+			   HWMON_PWM_AUTO_CHANNELS_TEMP,
+			   HWMON_PWM_AUTO_CHANNELS_TEMP,
+			   HWMON_PWM_AUTO_CHANNELS_TEMP
+			   ),
 	HWMON_CHANNEL_INFO(in,
 			   HWMON_I_INPUT | HWMON_I_LABEL,
 			   HWMON_I_INPUT | HWMON_I_LABEL,