[PATCH v2 19/19] iio: chemical: bme680: Refactorize reading functions

From: Vasileios Amoiridis
Date: Thu Jun 06 2024 - 17:29:57 EST

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The reading of the pressure and humidity value, requires an update
of the t_fine variable which happens by reading the temperature
value.

So the bme680_read_{press/humid}() functions of the above sensors
are internally calling the equivalent bme680_read_temp() function
in order to update the t_fine value. By just looking at the code
this relation is a bit hidden and is not easy to understand why
those channels are not independent.

This commit tries to clear these thing a bit by splitting the
bme680_{read/compensate}_{temp/press/humid}() to the following:

i. bme680_read_{temp/press/humid}_adc(): read the raw value from
the sensor.

ii. bme680_calc_t_fine(): calculate the t_fine variable.

iii. bme680_get_t_fine(): get the t_fine variable.

iv. bme680_compensate_{temp/press/humid}(): compensate the adc
values and return the calculated value.

v. bme680_read_{temp/press/humid}(): combine calls of the
aforementioned functions to return the requested value.

Signed-off-by: Vasileios Amoiridis <vassilisamir@xxxxxxxxx>
---
drivers/iio/chemical/bme680_core.c | 192 +++++++++++++++++------------
1 file changed, 116 insertions(+), 76 deletions(-)

diff --git a/drivers/iio/chemical/bme680_core.c b/drivers/iio/chemical/bme680_core.c
index b654a8cd31aa..6d0069d2dfb2 100644
--- a/drivers/iio/chemical/bme680_core.c
+++ b/drivers/iio/chemical/bme680_core.c
@@ -104,11 +104,6 @@ struct bme680_data {
u8 oversampling_humid;
u16 heater_dur;
u16 heater_temp;
- /*
- * Carryover value from temperature conversion, used in pressure
- * and humidity compensation calculations.
- */
- s32 t_fine;

union {
u8 buf[3];
@@ -237,6 +232,31 @@ static int bme680_read_calib(struct bme680_data *data,
return 0;
}

+static int bme680_read_temp_adc(struct bme680_data *data, u32 *adc_temp)
+{
+ struct device *dev = regmap_get_device(data->regmap);
+ u32 value_temp;
+ int ret;
+
+ ret = regmap_bulk_read(data->regmap, BME680_REG_TEMP_MSB,
+ data->buf, BME680_TEMP_NUM_BYTES);
+ if (ret < 0) {
+ dev_err(dev, "failed to read temperature\n");
+ return ret;
+ }
+
+ value_temp = FIELD_GET(BME680_MEAS_TRIM_MASK,
+ get_unaligned_be24(data->buf));
+ if (value_temp == BME680_MEAS_SKIPPED) {
+ /* reading was skipped */
+ dev_err(dev, "reading temperature skipped\n");
+ return -EINVAL;
+ }
+ *adc_temp = value_temp;
+
+ return 0;
+}
+
/*
* Taken from Bosch BME680 API:
* https://github.com/BoschSensortec/BME680_driver/blob/63bb5336/bme680.c#L876
@@ -244,12 +264,10 @@ static int bme680_read_calib(struct bme680_data *data,
* Returns temperature measurement in DegC, resolutions is 0.01 DegC. Therefore,
* output value of "3233" represents 32.33 DegC.
*/
-static s16 bme680_compensate_temp(struct bme680_data *data,
- u32 adc_temp)
+static s32 bme680_calc_t_fine(struct bme680_data *data, u32 adc_temp)
{
struct bme680_calib *calib = &data->bme680;
s64 var1, var2, var3;
- s16 calc_temp;

/* If the calibration is invalid, attempt to reload it */
if (!calib->par_t2)
@@ -259,10 +277,52 @@ static s16 bme680_compensate_temp(struct bme680_data *data,
var2 = (var1 * calib->par_t2) >> 11;
var3 = ((var1 >> 1) * (var1 >> 1)) >> 12;
var3 = (var3 * ((s32)calib->par_t3 << 4)) >> 14;
- data->t_fine = var2 + var3;
- calc_temp = (data->t_fine * 5 + 128) >> 8;
+ return var2 + var3; /* t_fine = var2 + var3 */
+}
+
+static int bme680_get_t_fine(struct bme680_data *data, s32 *t_fine)
+{
+ u32 adc_temp;
+ int ret;
+
+ ret = bme680_read_temp_adc(data, &adc_temp);
+ if (ret)
+ return ret;
+
+ *t_fine = bme680_calc_t_fine(data, adc_temp);
+
+ return 0;
+}

- return calc_temp;
+static s16 bme680_compensate_temp(struct bme680_data *data,
+ u32 adc_temp)
+{
+ return (bme680_calc_t_fine(data, adc_temp) * 5 + 128) / 256;
+}
+
+static int bme680_read_press_adc(struct bme680_data *data, u32 *adc_press)
+{
+ struct device *dev = regmap_get_device(data->regmap);
+ u32 value_press;
+ int ret;
+
+ ret = regmap_bulk_read(data->regmap, BME680_REG_PRESS_MSB,
+ data->buf, BME680_PRESS_NUM_BYTES);
+ if (ret < 0) {
+ dev_err(dev, "failed to read pressure\n");
+ return ret;
+ }
+
+ value_press = FIELD_GET(BME680_MEAS_TRIM_MASK,
+ get_unaligned_be24(data->buf));
+ if (value_press == BME680_MEAS_SKIPPED) {
+ /* reading was skipped */
+ dev_err(dev, "reading pressure skipped\n");
+ return -EINVAL;
+ }
+ *adc_press = value_press;
+
+ return 0;
}

/*
@@ -273,12 +333,12 @@ static s16 bme680_compensate_temp(struct bme680_data *data,
* 97356 Pa = 973.56 hPa.
*/
static u32 bme680_compensate_press(struct bme680_data *data,
- u32 adc_press)
+ u32 adc_press, s32 t_fine)
{
struct bme680_calib *calib = &data->bme680;
s32 var1, var2, var3, press_comp;

- var1 = (data->t_fine >> 1) - 64000;
+ var1 = (t_fine >> 1) - 64000;
var2 = ((((var1 >> 2) * (var1 >> 2)) >> 11) * calib->par_p6) >> 2;
var2 = var2 + (var1 * calib->par_p5 << 1);
var2 = (var2 >> 2) + ((s32)calib->par_p4 << 16);
@@ -306,6 +366,30 @@ static u32 bme680_compensate_press(struct bme680_data *data,
return press_comp;
}

+static int bme680_read_humid_adc(struct bme680_data *data, u32 *adc_humidity)
+{
+ struct device *dev = regmap_get_device(data->regmap);
+ u32 value_humidity;
+ int ret;
+
+ ret = regmap_bulk_read(data->regmap, BME680_REG_HUMIDITY_MSB,
+ &data->be16, BME680_HUMID_NUM_BYTES);
+ if (ret < 0) {
+ dev_err(dev, "failed to read humidity\n");
+ return ret;
+ }
+
+ value_humidity = be16_to_cpu(data->be16);
+ if (value_humidity == BME680_MEAS_SKIPPED) {
+ /* reading was skipped */
+ dev_err(dev, "reading humidity skipped\n");
+ return -EINVAL;
+ }
+ *adc_humidity = value_humidity;
+
+ return 0;
+}
+
/*
* Taken from Bosch BME680 API:
* https://github.com/BoschSensortec/BME680_driver/blob/63bb5336/bme680.c#L937
@@ -314,12 +398,12 @@ static u32 bme680_compensate_press(struct bme680_data *data,
* value of "43215" represents 43.215 %rH.
*/
static u32 bme680_compensate_humid(struct bme680_data *data,
- u16 adc_humid)
+ u16 adc_humid, s32 t_fine)
{
struct bme680_calib *calib = &data->bme680;
s32 var1, var2, var3, var4, var5, var6, temp_scaled, calc_hum;

- temp_scaled = (data->t_fine * 5 + 128) >> 8;
+ temp_scaled = (t_fine * 5 + 128) >> 8;
var1 = (adc_humid - (((s32)calib->par_h1 * 16))) -
(((temp_scaled * calib->par_h3) / 100) >> 1);
var2 = (calib->par_h2 *
@@ -567,68 +651,35 @@ static int bme680_gas_config(struct bme680_data *data)

static int bme680_read_temp(struct bme680_data *data, int *val)
{
- struct device *dev = regmap_get_device(data->regmap);
int ret;
u32 adc_temp;
s16 comp_temp;

- ret = regmap_bulk_read(data->regmap, BME680_REG_TEMP_MSB,
- data->buf, BME680_TEMP_NUM_BYTES);
- if (ret < 0) {
- dev_err(dev, "failed to read temperature\n");
+ ret = bme680_read_temp_adc(data, &adc_temp);
+ if (ret)
return ret;
- }

- adc_temp = FIELD_GET(BME680_MEAS_TRIM_MASK,
- get_unaligned_be24(data->buf));
- if (adc_temp == BME680_MEAS_SKIPPED) {
- /* reading was skipped */
- dev_err(dev, "reading temperature skipped\n");
- return -EINVAL;
- }
comp_temp = bme680_compensate_temp(data, adc_temp);
- /*
- * val might be NULL if we're called by the read_press/read_humid
- * routine which is called to get t_fine value used in
- * compensate_press/compensate_humid to get compensated
- * pressure/humidity readings.
- */
- if (val) {
- *val = comp_temp * 10; /* Centidegrees to millidegrees */
- return IIO_VAL_INT;
- }
-
- return ret;
+ *val = comp_temp * 10; /* Centidegrees to millidegrees */
+ return IIO_VAL_INT;
}

static int bme680_read_press(struct bme680_data *data,
int *val, int *val2)
{
- struct device *dev = regmap_get_device(data->regmap);
int ret;
u32 adc_press;
+ s32 t_fine;

- /* Read and compensate temperature to get a reading of t_fine */
- ret = bme680_read_temp(data, NULL);
- if (ret < 0)
+ ret = bme680_get_t_fine(data, &t_fine);
+ if (ret)
return ret;

- ret = regmap_bulk_read(data->regmap, BME680_REG_PRESS_MSB,
- data->buf, BME680_PRESS_NUM_BYTES);
- if (ret < 0) {
- dev_err(dev, "failed to read pressure\n");
+ ret = bme680_read_press_adc(data, &adc_press);
+ if (ret)
return ret;
- }
-
- adc_press = FIELD_GET(BME680_MEAS_TRIM_MASK,
- get_unaligned_be24(data->buf));
- if (adc_press == BME680_MEAS_SKIPPED) {
- /* reading was skipped */
- dev_err(dev, "reading pressure skipped\n");
- return -EINVAL;
- }

- *val = bme680_compensate_press(data, adc_press);
+ *val = bme680_compensate_press(data, adc_press, t_fine);
*val2 = 1000;
return IIO_VAL_FRACTIONAL;
}
@@ -636,30 +687,19 @@ static int bme680_read_press(struct bme680_data *data,
static int bme680_read_humid(struct bme680_data *data,
int *val, int *val2)
{
- struct device *dev = regmap_get_device(data->regmap);
int ret;
- u16 adc_humidity;
- u32 comp_humidity;
+ u32 adc_humidity, comp_humidity;
+ s32 t_fine;

- /* Read and compensate temperature to get a reading of t_fine */
- ret = bme680_read_temp(data, NULL);
- if (ret < 0)
+ ret = bme680_get_t_fine(data, &t_fine);
+ if (ret)
return ret;

- ret = regmap_bulk_read(data->regmap, BME680_REG_HUMIDITY_MSB,
- &data->be16, BME680_HUMID_NUM_BYTES);
- if (ret < 0) {
- dev_err(dev, "failed to read humidity\n");
+ ret = bme680_read_humid_adc(data, &adc_humidity);
+ if (ret)
return ret;
- }

- adc_humidity = be16_to_cpu(data->be16);
- if (adc_humidity == BME680_MEAS_SKIPPED) {
- /* reading was skipped */
- dev_err(dev, "reading humidity skipped\n");
- return -EINVAL;
- }
- comp_humidity = bme680_compensate_humid(data, adc_humidity);
+ comp_humidity = bme680_compensate_humid(data, adc_humidity, t_fine);

*val = comp_humidity;
*val2 = 1000;
--
2.25.1

Next message: Frank Li: "Re: [PATCH v5 00/12] PCI: imx6: Fix\rename\clean up and add lut information for imx95"
Previous message: Vasileios Amoiridis: "[PATCH v2 18/19] iio: chemical: bme680: Move forced mode setup in ->read_raw()"
In reply to: Vasileios Amoiridis: "[PATCH v2 18/19] iio: chemical: bme680: Move forced mode setup in ->read_raw()"
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