[PATCH 5.4 20/56] hwmon: (tmp421) report /PVLD condition as fault

[Greg Kroah-Hartman]

From: Paul Fertser <fercerpav@xxxxxxxxx>

[ Upstream commit 540effa7f283d25bcc13c0940d808002fee340b8 ]

For both local and remote sensors all the supported ICs can report an
"undervoltage lockout" condition which means the conversion wasn't
properly performed due to insufficient power supply voltage and so the
measurement results can't be trusted.

Fixes: 9410700b881f ("hwmon: Add driver for Texas Instruments TMP421/422/423 sensor chips")
Signed-off-by: Paul Fertser <fercerpav@xxxxxxxxx>
Link: https://lore.kernel.org/r/20210924093011.26083-2-fercerpav@xxxxxxxxx
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/hwmon/tmp421.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/hwmon/tmp421.c b/drivers/hwmon/tmp421.c
index a94e35cff3e5..e245ae272f7d 100644
--- a/drivers/hwmon/tmp421.c
+++ b/drivers/hwmon/tmp421.c
@@ -160,10 +160,10 @@ static int tmp421_read(struct device *dev, enum hwmon_sensor_types type,
 		return 0;
 	case hwmon_temp_fault:
 		/*
-		 * The OPEN bit signals a fault. This is bit 0 of the temperature
-		 * register (low byte).
+		 * Any of OPEN or /PVLD bits indicate a hardware mulfunction
+		 * and the conversion result may be incorrect
 		 */
-		*val = tmp421->temp[channel] & 0x01;
+		*val = !!(tmp421->temp[channel] & 0x03);
 		return 0;
 	default:
 		return -EOPNOTSUPP;
@@ -176,9 +176,6 @@ static umode_t tmp421_is_visible(const void *data, enum hwmon_sensor_types type,
 {
 	switch (attr) {
 	case hwmon_temp_fault:
-		if (channel == 0)
-			return 0;
-		return 0444;
 	case hwmon_temp_input:
 		return 0444;
 	default:
-- 
2.33.0