staging iio adt7410: fix 13bit mode

The driver assumes that in 13bit mode the 16bit value has
to be shifted to the right by 3 bits. This is not true, in
both 16bit and 13bit mode the MSB is at the same position.
Currently the driver returns a temperature of 194 degrees
Celsius in 13bit mode and 24 degrees Celsius in 16bit mode.
Fix this by using the same algorithm for 16bit and 13bit
mode and by just masking out the lower three bits in 13bit
mode.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/drivers/staging/iio/adc/adt7410.c b/drivers/staging/iio/adc/adt7410.c
index 9025161dfe0e361b5d74050479d66140bf15c8f0..f87992cd1accb798f8fa17a8573996bc73a72072 100644 (file)
--- a/drivers/staging/iio/adc/adt7410.c
+++ b/drivers/staging/iio/adc/adt7410.c
@@ -293,26 +293,17 @@ static ssize_t adt7410_convert_temperature(struct adt7410_chip_info *chip,
 {
        char sign = ' ';
 
-       if (chip->config & ADT7410_RESOLUTION) {
-               if (data & ADT7410_T16_VALUE_SIGN) {
-                       /* convert supplement to positive value */
-                       data = (u16)((ADT7410_T16_VALUE_SIGN << 1) - (u32)data);
-                       sign = '-';
-               }
-               return sprintf(buf, "%c%d.%.7d\n", sign,
-                               (data >> ADT7410_T16_VALUE_FLOAT_OFFSET),
-                               (data & ADT7410_T16_VALUE_FLOAT_MASK) * 78125);
-       } else {
-               if (data & ADT7410_T13_VALUE_SIGN) {
-                       /* convert supplement to positive value */
-                       data >>= ADT7410_T13_VALUE_OFFSET;
-                       data = (ADT7410_T13_VALUE_SIGN << 1) - data;
-                       sign = '-';
-               }
-               return sprintf(buf, "%c%d.%.4d\n", sign,
-                               (data >> ADT7410_T13_VALUE_FLOAT_OFFSET),
-                               (data & ADT7410_T13_VALUE_FLOAT_MASK) * 625);
+       if (!(chip->config & ADT7410_RESOLUTION))
+               data &= ~0x7;
+
+       if (data & ADT7410_T16_VALUE_SIGN) {
+               /* convert supplement to positive value */
+               data = (u16)((ADT7410_T16_VALUE_SIGN << 1) - (u32)data);
+               sign = '-';
        }
+       return sprintf(buf, "%c%d.%.7d\n", sign,
+                       (data >> ADT7410_T16_VALUE_FLOAT_OFFSET),
+                       (data & ADT7410_T16_VALUE_FLOAT_MASK) * 78125);
 }
 
 static ssize_t adt7410_show_value(struct device *dev,