[PATCH hwmon 1/1] hwmon: (mlxreg-fan) Return zero speed for broken fan

From: Vadim Pasternak <vadimp@nvidia.com>
To: <linux@roeck-us.net>
Cc: <linux-hwmon@vger.kernel.org>, Vadim Pasternak <vadimp@nvidia.com>
Subject: [PATCH hwmon 1/1] hwmon: (mlxreg-fan) Return zero speed for broken fan
Date: Sun, 12 Feb 2023 16:57:30 +0200	[thread overview]
Message-ID: <20230212145730.24247-1-vadimp@nvidia.com> (raw)

Currently for broken fan driver returns value calculated based on error
code (0xFF) in related fan speed register.
Thus, for such fan user gets fan{n}_fault to 1 and fan{n}_input with
misleading value.

Add check for fan fault prior return speed value and return zero if
fault is detected.

Fixes: 65afb4c8e7e4 ("hwmon: (mlxreg-fan) Add support for Mellanox FAN driver")
Signed-off-by: Vadim Pasternak <vadimp@nvidia.com>
---
 drivers/hwmon/mlxreg-fan.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/hwmon/mlxreg-fan.c b/drivers/hwmon/mlxreg-fan.c
index b48bd7c961d6..96017cc8da7e 100644
--- a/drivers/hwmon/mlxreg-fan.c
+++ b/drivers/hwmon/mlxreg-fan.c
@@ -155,6 +155,12 @@ mlxreg_fan_read(struct device *dev, enum hwmon_sensor_types type, u32 attr,
 			if (err)
 				return err;
 
+			if (MLXREG_FAN_GET_FAULT(regval, tacho->mask)) {
+				/* FAN is broken - return zero for FAN speed. */
+				*val = 0;
+				return 0;
+			}
+
 			*val = MLXREG_FAN_GET_RPM(regval, fan->divider,
 						  fan->samples);
 			break;
-- 
2.20.1

