hwmon: (pmbus) Fix low limit temperature alarms

Temperature alarms are detected by checking the alarm bit and comparing
temperature limits against the current temperature. For low limits, this
comparison needs to be reversed (temp < limit instead of temp > limit).
This was not taken into account, resulting in wrong alarms if a temperature
fell below a low limit.

Fix by adding a low limit flag in the limit data structure. When creating the
sensor entry, the order of registers to compare is now reversed for low limits.

Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>
Acked-by: Jean Delvare <khali@linux-fr.org>
Cc: stable@kernel.org # 3.0+

drivers/hwmon/pmbus/pmbus_core.c

@@ -978,6 +978,8 @@ static void pmbus_find_max_attr(struct i2c_client *client,
 struct pmbus_limit_attr {
 	u16 reg;		/* Limit register */
 	bool update;		/* True if register needs updates */
+	bool low;		/* True if low limit; for limits with compare
+				   functions only */
 	const char *attr;	/* Attribute name */
 	const char *alarm;	/* Alarm attribute name */
 	u32 sbit;		/* Alarm attribute status bit */
@@ -1029,7 +1031,8 @@ static bool pmbus_add_limit_attrs(struct i2c_client *client,
 				if (attr->compare) {
 					pmbus_add_boolean_cmp(data, name,
 						l->alarm, index,
-						cbase, cindex,
+						l->low ? cindex : cbase,
+						l->low ? cbase : cindex,
 						attr->sbase + page, l->sbit);
 				} else {
 					pmbus_add_boolean_reg(data, name,
@@ -1366,11 +1369,13 @@ static const struct pmbus_sensor_attr power_attributes[] = {
 static const struct pmbus_limit_attr temp_limit_attrs[] = {
 	{
 		.reg = PMBUS_UT_WARN_LIMIT,
+		.low = true,
 		.attr = "min",
 		.alarm = "min_alarm",
 		.sbit = PB_TEMP_UT_WARNING,
 	}, {
 		.reg = PMBUS_UT_FAULT_LIMIT,
+		.low = true,
 		.attr = "lcrit",
 		.alarm = "lcrit_alarm",
 		.sbit = PB_TEMP_UT_FAULT,
@@ -1399,11 +1404,13 @@ static const struct pmbus_limit_attr temp_limit_attrs[] = {
 static const struct pmbus_limit_attr temp_limit_attrs23[] = {
 	{
 		.reg = PMBUS_UT_WARN_LIMIT,
+		.low = true,
 		.attr = "min",
 		.alarm = "min_alarm",
 		.sbit = PB_TEMP_UT_WARNING,
 	}, {
 		.reg = PMBUS_UT_FAULT_LIMIT,
+		.low = true,
 		.attr = "lcrit",
 		.alarm = "lcrit_alarm",
 		.sbit = PB_TEMP_UT_FAULT,