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From: Vasileios Amoiridis <vassilisamir@gmail.com>
To: jic23@kernel.org
Cc: lars@metafoo.de,
	andriy.shevchenko@linux.intel.com,
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	semen.protsenko@linaro.org,
	linux-iio@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Vasileios Amoiridis <vassilisamir@gmail.com>
Subject: [PATCH v6 4/9] iio: pressure: bmp280: Use unsigned data types for raw sensor data
Date: Wed,  8 May 2024 18:52:02 +0200
Message-Id: <20240508165207.145554-5-vassilisamir@gmail.com>
In-Reply-To: <20240508165207.145554-1-vassilisamir@gmail.com>
References: <20240508165207.145554-1-vassilisamir@gmail.com>
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The raw sensor data that have not been compensated yet cannot be
signed values, so use unsigned ones. Also, compensated pressure
values cannot be negative so use unsigned also there.

Also, drop redundant cast of data->t_fine variable from s32 to s32.

Signed-off-by: Vasileios Amoiridis <vassilisamir@gmail.com>
---
 drivers/iio/pressure/bmp280-core.c | 45 +++++++++++++++---------------
 1 file changed, 22 insertions(+), 23 deletions(-)

diff --git a/drivers/iio/pressure/bmp280-core.c b/drivers/iio/pressure/bmp280-core.c
index f05ea754f53a..dd5c526dacbd 100644
--- a/drivers/iio/pressure/bmp280-core.c
+++ b/drivers/iio/pressure/bmp280-core.c
@@ -289,13 +289,13 @@ static int bme280_read_calib(struct bmp280_data *data)
  * Taken from BME280 datasheet, Section 4.2.3, "Compensation formula".
  */
 static u32 bme280_compensate_humidity(struct bmp280_data *data,
-				      s32 adc_humidity)
+				      u16 adc_humidity)
 {
 	struct bmp280_calib *calib = &data->calib.bmp280;
 	s32 var;
 
-	var = ((s32)data->t_fine) - (s32)76800;
-	var = ((((adc_humidity << 14) - (calib->H4 << 20) - (calib->H5 * var))
+	var = data->t_fine - (s32)76800;
+	var = (((((s32)adc_humidity << 14) - (calib->H4 << 20) - (calib->H5 * var))
 		+ (s32)16384) >> 15) * (((((((var * calib->H6) >> 10)
 		* (((var * (s32)calib->H3) >> 11) + (s32)32768)) >> 10)
 		+ (s32)2097152) * calib->H2 + 8192) >> 14);
@@ -314,16 +314,16 @@ static u32 bme280_compensate_humidity(struct bmp280_data *data,
  * Taken from datasheet, Section 3.11.3, "Compensation formula".
  */
 static s32 bmp280_compensate_temp(struct bmp280_data *data,
-				  s32 adc_temp)
+				  u32 adc_temp)
 {
 	struct bmp280_calib *calib = &data->calib.bmp280;
 	s32 var1, var2;
 
-	var1 = (((adc_temp >> 3) - ((s32)calib->T1 << 1)) *
+	var1 = (((((s32)adc_temp) >> 3) - ((s32)calib->T1 << 1)) *
 		((s32)calib->T2)) >> 11;
-	var2 = (((((adc_temp >> 4) - ((s32)calib->T1)) *
-		  ((adc_temp >> 4) - ((s32)calib->T1))) >> 12) *
-		((s32)calib->T3)) >> 14;
+	var2 = (((((((s32)adc_temp) >> 4) - ((s32)calib->T1)) *
+		  ((((s32)adc_temp >> 4) - ((s32)calib->T1))) >> 12) *
+		((s32)calib->T3))) >> 14;
 	data->t_fine = var1 + var2;
 
 	return (data->t_fine * 5 + 128) >> 8;
@@ -337,7 +337,7 @@ static s32 bmp280_compensate_temp(struct bmp280_data *data,
  * Taken from datasheet, Section 3.11.3, "Compensation formula".
  */
 static u32 bmp280_compensate_press(struct bmp280_data *data,
-				   s32 adc_press)
+				   u32 adc_press)
 {
 	struct bmp280_calib *calib = &data->calib.bmp280;
 	s64 var1, var2, p;
@@ -353,7 +353,7 @@ static u32 bmp280_compensate_press(struct bmp280_data *data,
 	if (var1 == 0)
 		return 0;
 
-	p = ((((s64)1048576 - adc_press) << 31) - var2) * 3125;
+	p = ((((s64)1048576 - (s32)adc_press) << 31) - var2) * 3125;
 	p = div64_s64(p, var1);
 	var1 = (((s64)calib->P9) * (p >> 13) * (p >> 13)) >> 25;
 	var2 = ((s64)(calib->P8) * p) >> 19;
@@ -365,7 +365,8 @@ static u32 bmp280_compensate_press(struct bmp280_data *data,
 static int bmp280_read_temp(struct bmp280_data *data,
 			    int *val, int *val2)
 {
-	s32 adc_temp, comp_temp;
+	s32 comp_temp;
+	u32 adc_temp;
 	int ret;
 
 	ret = regmap_bulk_read(data->regmap, BMP280_REG_TEMP_MSB,
@@ -398,8 +399,7 @@ static int bmp280_read_temp(struct bmp280_data *data,
 static int bmp280_read_press(struct bmp280_data *data,
 			     int *val, int *val2)
 {
-	u32 comp_press;
-	s32 adc_press;
+	u32 comp_press, adc_press;
 	int ret;
 
 	/* Read and compensate temperature so we get a reading of t_fine. */
@@ -431,7 +431,7 @@ static int bmp280_read_press(struct bmp280_data *data,
 static int bme280_read_humid(struct bmp280_data *data, int *val, int *val2)
 {
 	u32 comp_humidity;
-	s32 adc_humidity;
+	u16 adc_humidity;
 	int ret;
 
 	/* Read and compensate temperature so we get a reading of t_fine. */
@@ -1030,8 +1030,7 @@ static int bmp380_read_temp(struct bmp280_data *data, int *val, int *val2)
 
 static int bmp380_read_press(struct bmp280_data *data, int *val, int *val2)
 {
-	s32 comp_press;
-	u32 adc_press;
+	u32 adc_press, comp_press;
 	int ret;
 
 	/* Read and compensate for temperature so we get a reading of t_fine */
@@ -1893,12 +1892,12 @@ static int bmp180_read_calib(struct bmp280_data *data)
  *
  * Taken from datasheet, Section 3.5, "Calculating pressure and temperature".
  */
-static s32 bmp180_compensate_temp(struct bmp280_data *data, s32 adc_temp)
+static s32 bmp180_compensate_temp(struct bmp280_data *data, u32 adc_temp)
 {
 	struct bmp180_calib *calib = &data->calib.bmp180;
 	s32 x1, x2;
 
-	x1 = ((adc_temp - calib->AC6) * calib->AC5) >> 15;
+	x1 = ((((s32)adc_temp) - calib->AC6) * calib->AC5) >> 15;
 	x2 = (calib->MC << 11) / (x1 + calib->MD);
 	data->t_fine = x1 + x2;
 
@@ -1907,7 +1906,8 @@ static s32 bmp180_compensate_temp(struct bmp280_data *data, s32 adc_temp)
 
 static int bmp180_read_temp(struct bmp280_data *data, int *val, int *val2)
 {
-	s32 adc_temp, comp_temp;
+	s32 comp_temp;
+	u32 adc_temp;
 	int ret;
 
 	ret = bmp180_read_adc_temp(data, &adc_temp);
@@ -1957,7 +1957,7 @@ static int bmp180_read_adc_press(struct bmp280_data *data, int *val)
  *
  * Taken from datasheet, Section 3.5, "Calculating pressure and temperature".
  */
-static u32 bmp180_compensate_press(struct bmp280_data *data, s32 adc_press)
+static u32 bmp180_compensate_press(struct bmp280_data *data, u32 adc_press)
 {
 	struct bmp180_calib *calib = &data->calib.bmp180;
 	s32 oss = data->oversampling_press;
@@ -1974,7 +1974,7 @@ static u32 bmp180_compensate_press(struct bmp280_data *data, s32 adc_press)
 	x2 = (calib->B1 * ((b6 * b6) >> 12)) >> 16;
 	x3 = (x1 + x2 + 2) >> 2;
 	b4 = calib->AC4 * (u32)(x3 + 32768) >> 15;
-	b7 = ((u32)adc_press - b3) * (50000 >> oss);
+	b7 = (adc_press - b3) * (50000 >> oss);
 	if (b7 < 0x80000000)
 		p = (b7 * 2) / b4;
 	else
@@ -1989,8 +1989,7 @@ static u32 bmp180_compensate_press(struct bmp280_data *data, s32 adc_press)
 
 static int bmp180_read_press(struct bmp280_data *data, int *val, int *val2)
 {
-	u32 comp_press;
-	s32 adc_press;
+	u32 comp_press, adc_press;
 	int ret;
 
 	/* Read and compensate temperature so we get a reading of t_fine. */
-- 
2.25.1