[PATCH v2 1/1] hwmon: (isl28022) Fix current reading calculation

[Yikai Tsai]

According to the ISL28022 datasheet, bit15 of the current register is
representing -32768. Fix the calculation to properly handle this bit,
ensuring correct measurements for negative values.

Signed-off-by: Yikai Tsai <yikai.tsai.wiwynn@xxxxxxxxx>
---
 drivers/hwmon/isl28022.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/hwmon/isl28022.c b/drivers/hwmon/isl28022.c
index 1fb9864635db..1b4fb0824d6c 100644
--- a/drivers/hwmon/isl28022.c
+++ b/drivers/hwmon/isl28022.c
@@ -154,6 +154,7 @@ static int isl28022_read_current(struct device *dev, u32 attr, long *val)
 	struct isl28022_data *data = dev_get_drvdata(dev);
 	unsigned int regval;
 	int err;
+	u16 sign_bit;
 
 	switch (attr) {
 	case hwmon_curr_input:
@@ -161,8 +162,9 @@ static int isl28022_read_current(struct device *dev, u32 attr, long *val)
 				  ISL28022_REG_CURRENT, &regval);
 		if (err < 0)
 			return err;
-		*val = ((long)regval * 1250L * (long)data->gain) /
-			(long)data->shunt;
+		sign_bit = (regval >> 15) & 0x01;
+		*val = (((long)(((u16)regval) & 0x7FFF) - (sign_bit * 32768)) *
+			1250L * (long)data->gain) / (long)data->shunt;
 		break;
 	default:
 		return -EOPNOTSUPP;
-- 
2.25.1