hwmon: (pmbus) Add Vin unit off handling

If there is an input undervoltage fault, reported in STATUS_INPUT
command response, there is quite likely a "Unit Off For Insufficient
Input Voltage" condition as well.

Add a constant for bit 3 of STATUS_INPUT. Update the Vin limit
attributes to include both bits in the mask for clearing faults.

If an input undervoltage fault occurs, causing a unit off for
insufficient input voltage, but the unit is off bit is not cleared, the
STATUS_WORD will not be updated to clear the input fault condition.
Including the unit is off bit (bit 3) allows for the input fault
condition to completely clear.
Signed-off-by: Brandon Wyman <bjwyman@gmail.com>
Link: https://lore.kernel.org/r/20220317232123.2103592-1-bjwyman@gmail.com
Fixes: b4ce237b ("hwmon: (pmbus) Introduce infrastructure to detect sensors and limit registers")
[groeck: Dropped unnecessary ()]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/pmbus/pmbus.h

@@ -319,6 +319,7 @@ enum pmbus_fan_mode { percent = 0, rpm };
 /*
  * STATUS_VOUT, STATUS_INPUT
  */
+#define PB_VOLTAGE_VIN_OFF		BIT(3)
 #define PB_VOLTAGE_UV_FAULT		BIT(4)
 #define PB_VOLTAGE_UV_WARNING		BIT(5)
 #define PB_VOLTAGE_OV_WARNING		BIT(6)

drivers/hwmon/pmbus/pmbus_core.c

@@ -1373,7 +1373,7 @@ static const struct pmbus_limit_attr vin_limit_attrs[] = {
 		.reg = PMBUS_VIN_UV_FAULT_LIMIT,
 		.attr = "lcrit",
 		.alarm = "lcrit_alarm",
-		.sbit = PB_VOLTAGE_UV_FAULT,
+		.sbit = PB_VOLTAGE_UV_FAULT | PB_VOLTAGE_VIN_OFF,
 	}, {
 		.reg = PMBUS_VIN_OV_WARN_LIMIT,
 		.attr = "max",