summaryrefslogtreecommitdiff
path: root/drivers/iio/humidity/hdc3020.c
diff options
context:
space:
mode:
Diffstat (limited to 'drivers/iio/humidity/hdc3020.c')
-rw-r--r--drivers/iio/humidity/hdc3020.c73
1 files changed, 43 insertions, 30 deletions
diff --git a/drivers/iio/humidity/hdc3020.c b/drivers/iio/humidity/hdc3020.c
index ffb25596d3a8..78b2c171c8da 100644
--- a/drivers/iio/humidity/hdc3020.c
+++ b/drivers/iio/humidity/hdc3020.c
@@ -72,6 +72,9 @@
#define HDC3020_MAX_TEMP_HYST_MICRO 164748607
#define HDC3020_MAX_HUM_MICRO 99220264
+/* Divide 65535 from the datasheet by 5 to avoid overflows */
+#define HDC3020_THRESH_FRACTION (65535 / 5)
+
struct hdc3020_data {
struct i2c_client *client;
struct gpio_desc *reset_gpio;
@@ -301,9 +304,9 @@ static int hdc3020_read_raw(struct iio_dev *indio_dev,
case IIO_CHAN_INFO_SCALE:
*val2 = 65536;
if (chan->type == IIO_TEMP)
- *val = 175;
+ *val = 175 * MILLI;
else
- *val = 100;
+ *val = 100 * MILLI;
return IIO_VAL_FRACTIONAL;
case IIO_CHAN_INFO_OFFSET:
@@ -376,15 +379,18 @@ static int hdc3020_thresh_get_temp(u16 thresh)
int temp;
/*
- * Get the temperature threshold from 9 LSBs, shift them to get
- * the truncated temperature threshold representation and
- * calculate the threshold according to the formula in the
- * datasheet. Result is degree celsius scaled by 65535.
+ * Get the temperature threshold from 9 LSBs, shift them to get the
+ * truncated temperature threshold representation and calculate the
+ * threshold according to the explicit formula in the datasheet:
+ * T(C) = -45 + (175 * temp) / 65535.
+ * Additionally scale by HDC3020_THRESH_FRACTION to avoid precision loss
+ * when calculating threshold and hysteresis values. Result is degree
+ * celsius scaled by HDC3020_THRESH_FRACTION.
*/
temp = FIELD_GET(HDC3020_THRESH_TEMP_MASK, thresh) <<
HDC3020_THRESH_TEMP_TRUNC_SHIFT;
- return -2949075 + (175 * temp);
+ return -2949075 / 5 + (175 / 5 * temp);
}
static int hdc3020_thresh_get_hum(u16 thresh)
@@ -394,13 +400,16 @@ static int hdc3020_thresh_get_hum(u16 thresh)
/*
* Get the humidity threshold from 7 MSBs, shift them to get the
* truncated humidity threshold representation and calculate the
- * threshold according to the formula in the datasheet. Result is
- * percent scaled by 65535.
+ * threshold according to the explicit formula in the datasheet:
+ * RH(%) = 100 * hum / 65535.
+ * Additionally scale by HDC3020_THRESH_FRACTION to avoid precision loss
+ * when calculating threshold and hysteresis values. Result is percent
+ * scaled by HDC3020_THRESH_FRACTION.
*/
hum = FIELD_GET(HDC3020_THRESH_HUM_MASK, thresh) <<
HDC3020_THRESH_HUM_TRUNC_SHIFT;
- return hum * 100;
+ return hum * 100 / 5;
}
static u16 hdc3020_thresh_set_temp(int s_temp, u16 curr_thresh)
@@ -455,8 +464,8 @@ int hdc3020_thresh_clr(s64 s_thresh, s64 s_hyst, enum iio_event_direction dir)
else
s_clr = s_thresh + s_hyst;
- /* Divide by 65535 to get units of micro */
- return div_s64(s_clr, 65535);
+ /* Divide by HDC3020_THRESH_FRACTION to get units of micro */
+ return div_s64(s_clr, HDC3020_THRESH_FRACTION);
}
static int _hdc3020_write_thresh(struct hdc3020_data *data, u16 reg, u16 val)
@@ -507,7 +516,7 @@ static int hdc3020_write_thresh(struct iio_dev *indio_dev,
clr = ret;
/* Scale value to include decimal part into calculations */
- s_val = (val < 0) ? (val * 1000000 - val2) : (val * 1000000 + val2);
+ s_val = (val < 0) ? (val * 1000 - val2) : (val * 1000 + val2);
switch (chan->type) {
case IIO_TEMP:
switch (info) {
@@ -523,7 +532,8 @@ static int hdc3020_write_thresh(struct iio_dev *indio_dev,
/* Calculate old hysteresis */
s_thresh = (s64)hdc3020_thresh_get_temp(thresh) * 1000000;
s_clr = (s64)hdc3020_thresh_get_temp(clr) * 1000000;
- s_hyst = div_s64(abs(s_thresh - s_clr), 65535);
+ s_hyst = div_s64(abs(s_thresh - s_clr),
+ HDC3020_THRESH_FRACTION);
/* Set new threshold */
thresh = reg_val;
/* Set old hysteresis */
@@ -532,16 +542,17 @@ static int hdc3020_write_thresh(struct iio_dev *indio_dev,
case IIO_EV_INFO_HYSTERESIS:
/*
* Function hdc3020_thresh_get_temp returns temperature
- * in degree celsius scaled by 65535. Scale by 1000000
- * to be able to subtract scaled hysteresis value.
+ * in degree celsius scaled by HDC3020_THRESH_FRACTION.
+ * Scale by 1000000 to be able to subtract scaled
+ * hysteresis value.
*/
s_thresh = (s64)hdc3020_thresh_get_temp(thresh) * 1000000;
/*
* Units of s_val are in micro degree celsius, scale by
- * 65535 to get same units as s_thresh.
+ * HDC3020_THRESH_FRACTION to get same units as s_thresh.
*/
s_val = min(abs(s_val), HDC3020_MAX_TEMP_HYST_MICRO);
- s_hyst = (s64)s_val * 65535;
+ s_hyst = (s64)s_val * HDC3020_THRESH_FRACTION;
s_clr = hdc3020_thresh_clr(s_thresh, s_hyst, dir);
s_clr = max(s_clr, HDC3020_MIN_TEMP_MICRO);
s_clr = min(s_clr, HDC3020_MAX_TEMP_MICRO);
@@ -565,7 +576,8 @@ static int hdc3020_write_thresh(struct iio_dev *indio_dev,
/* Calculate old hysteresis */
s_thresh = (s64)hdc3020_thresh_get_hum(thresh) * 1000000;
s_clr = (s64)hdc3020_thresh_get_hum(clr) * 1000000;
- s_hyst = div_s64(abs(s_thresh - s_clr), 65535);
+ s_hyst = div_s64(abs(s_thresh - s_clr),
+ HDC3020_THRESH_FRACTION);
/* Set new threshold */
thresh = reg_val;
/* Try to set old hysteresis */
@@ -574,15 +586,16 @@ static int hdc3020_write_thresh(struct iio_dev *indio_dev,
case IIO_EV_INFO_HYSTERESIS:
/*
* Function hdc3020_thresh_get_hum returns relative
- * humidity in percent scaled by 65535. Scale by 1000000
- * to be able to subtract scaled hysteresis value.
+ * humidity in percent scaled by HDC3020_THRESH_FRACTION.
+ * Scale by 1000000 to be able to subtract scaled
+ * hysteresis value.
*/
s_thresh = (s64)hdc3020_thresh_get_hum(thresh) * 1000000;
/*
- * Units of s_val are in micro percent, scale by 65535
- * to get same units as s_thresh.
+ * Units of s_val are in micro percent, scale by
+ * HDC3020_THRESH_FRACTION to get same units as s_thresh.
*/
- s_hyst = (s64)s_val * 65535;
+ s_hyst = (s64)s_val * HDC3020_THRESH_FRACTION;
s_clr = hdc3020_thresh_clr(s_thresh, s_hyst, dir);
s_clr = max(s_clr, 0);
s_clr = min(s_clr, HDC3020_MAX_HUM_MICRO);
@@ -630,7 +643,7 @@ static int hdc3020_read_thresh(struct iio_dev *indio_dev,
thresh = hdc3020_thresh_get_temp(ret);
switch (info) {
case IIO_EV_INFO_VALUE:
- *val = thresh;
+ *val = thresh * MILLI;
break;
case IIO_EV_INFO_HYSTERESIS:
ret = hdc3020_read_be16(data, reg_clr);
@@ -638,18 +651,18 @@ static int hdc3020_read_thresh(struct iio_dev *indio_dev,
return ret;
clr = hdc3020_thresh_get_temp(ret);
- *val = abs(thresh - clr);
+ *val = abs(thresh - clr) * MILLI;
break;
default:
return -EOPNOTSUPP;
}
- *val2 = 65535;
+ *val2 = HDC3020_THRESH_FRACTION;
return IIO_VAL_FRACTIONAL;
case IIO_HUMIDITYRELATIVE:
thresh = hdc3020_thresh_get_hum(ret);
switch (info) {
case IIO_EV_INFO_VALUE:
- *val = thresh;
+ *val = thresh * MILLI;
break;
case IIO_EV_INFO_HYSTERESIS:
ret = hdc3020_read_be16(data, reg_clr);
@@ -657,12 +670,12 @@ static int hdc3020_read_thresh(struct iio_dev *indio_dev,
return ret;
clr = hdc3020_thresh_get_hum(ret);
- *val = abs(thresh - clr);
+ *val = abs(thresh - clr) * MILLI;
break;
default:
return -EOPNOTSUPP;
}
- *val2 = 65535;
+ *val2 = HDC3020_THRESH_FRACTION;
return IIO_VAL_FRACTIONAL;
default:
return -EOPNOTSUPP;
generated by cgit v1.2.3 (git 2.46.0) at 2025-12-03 06:40:17 +0000