Commit d2651a43 authored by Vasileios Amoiridis's avatar Vasileios Amoiridis Committed by Jonathan Cameron
Browse files

iio: chemical: bme680: Refactorize reading functions 



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: default avatarVasileios Amoiridis <vassilisamir@gmail.com>
Link: https://patch.msgid.link/20240609233826.330516-16-vassilisamir@gmail.com


Signed-off-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
parent ed4bb53c

drivers/iio/chemical/bme680_core.c

+116 −76
Original line number Diff line number Diff line
@@ -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;



	return calc_temp;

	ret = bme680_read_temp_adc(data, &adc_temp);

	if (ret)

		return ret;



	*t_fine = bme680_calc_t_fine(data, adc_temp);



	return 0;

}



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;

}



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;