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Commit 0f8994b1 authored by Vlad Dogaru's avatar Vlad Dogaru Committed by Jonathan Cameron
Browse files

iio: bmp280: refactor compensation code 



This version of the code avoids extra memory copy operations and is
somewhat smaller in code size.

Signed-off-by: default avatarVlad Dogaru <vlad.dogaru@intel.com>
Acked-by: default avatarHartmut Knaack <knaack.h@gmx.de>
Signed-off-by: default avatarJonathan Cameron <jic23@kernel.org>
parent 8f6eb025

drivers/iio/pressure/bmp280.c

+52 −88
Original line number Diff line number Diff line
@@ -80,16 +80,12 @@ struct bmp280_data { 
	s32 t_fine;

};



/* Compensation parameters. */

struct bmp280_comp_temp {

	u16 dig_t1;

	s16 dig_t2, dig_t3;

};



struct bmp280_comp_press {

	u16 dig_p1;

	s16 dig_p2, dig_p3, dig_p4, dig_p5, dig_p6, dig_p7, dig_p8, dig_p9;

};

/*

 * These enums are used for indexing into the array of compensation

 * parameters.

 */

enum { T1, T2, T3 };

enum { P1, P2, P3, P4, P5, P6, P7, P8, P9 };



static const struct iio_chan_spec bmp280_channels[] = {

	{
@@ -141,10 +137,18 @@ static const struct regmap_config bmp280_regmap_config = { 
	.volatile_reg = bmp280_is_volatile_reg,

};



static int bmp280_read_compensation_temp(struct bmp280_data *data,

					 struct bmp280_comp_temp *comp)

/*

 * Returns temperature in DegC, resolution is 0.01 DegC.  Output value of

 * "5123" equals 51.23 DegC.  t_fine carries fine temperature as global

 * value.

 *

 * Taken from datasheet, Section 3.11.3, "Compensation formula".

 */

static s32 bmp280_compensate_temp(struct bmp280_data *data,

				  s32 adc_temp)

{

	int ret;

	s32 var1, var2, t;

	__le16 buf[BMP280_COMP_TEMP_REG_COUNT / 2];



	ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_TEMP_START,
@@ -155,58 +159,19 @@ static int bmp280_read_compensation_temp(struct bmp280_data *data, 
		return ret;

	}



	comp->dig_t1 = (u16) le16_to_cpu(buf[0]);

	comp->dig_t2 = (s16) le16_to_cpu(buf[1]);

	comp->dig_t3 = (s16) le16_to_cpu(buf[2]);



	return 0;

}



static int bmp280_read_compensation_press(struct bmp280_data *data,

					  struct bmp280_comp_press *comp)

{

	int ret;

	__le16 buf[BMP280_COMP_PRESS_REG_COUNT / 2];



	ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_PRESS_START,

			       buf, BMP280_COMP_PRESS_REG_COUNT);

	if (ret < 0) {

		dev_err(&data->client->dev,

			"failed to read pressure calibration parameters\n");

		return ret;

	}



	comp->dig_p1 = (u16) le16_to_cpu(buf[0]);

	comp->dig_p2 = (s16) le16_to_cpu(buf[1]);

	comp->dig_p3 = (s16) le16_to_cpu(buf[2]);

	comp->dig_p4 = (s16) le16_to_cpu(buf[3]);

	comp->dig_p5 = (s16) le16_to_cpu(buf[4]);

	comp->dig_p6 = (s16) le16_to_cpu(buf[5]);

	comp->dig_p7 = (s16) le16_to_cpu(buf[6]);

	comp->dig_p8 = (s16) le16_to_cpu(buf[7]);

	comp->dig_p9 = (s16) le16_to_cpu(buf[8]);



	return 0;

}



	/*

 * Returns temperature in DegC, resolution is 0.01 DegC.  Output value of

 * "5123" equals 51.23 DegC.  t_fine carries fine temperature as global

 * value.

	 * The double casts are necessary because le16_to_cpu returns an

	 * unsigned 16-bit value.  Casting that value directly to a

	 * signed 32-bit will not do proper sign extension.

	 *

 * Taken from datasheet, Section 3.11.3, "Compensation formula".

	 * Conversely, T1 and P1 are unsigned values, so they can be

	 * cast straight to the larger type.

	 */

static s32 bmp280_compensate_temp(struct bmp280_data *data,

				  struct bmp280_comp_temp *comp,

				  s32 adc_temp)

{

	s32 var1, var2, t;



	var1 = (((adc_temp >> 3) - ((s32) comp->dig_t1 << 1)) *

		((s32) comp->dig_t2)) >> 11;

	var2 = (((((adc_temp >> 4) - ((s32) comp->dig_t1)) *

		  ((adc_temp >> 4) - ((s32) comp->dig_t1))) >> 12) *

		((s32) comp->dig_t3)) >> 14;

	var1 = (((adc_temp >> 3) - ((s32)le16_to_cpu(buf[T1]) << 1)) *

		((s32)(s16)le16_to_cpu(buf[T2]))) >> 11;

	var2 = (((((adc_temp >> 4) - ((s32)le16_to_cpu(buf[T1]))) *

		  ((adc_temp >> 4) - ((s32)le16_to_cpu(buf[T1])))) >> 12) *

		((s32)(s16)le16_to_cpu(buf[T3]))) >> 14;



	data->t_fine = var1 + var2;

	t = (data->t_fine * 5 + 128) >> 8;
@@ -222,27 +187,36 @@ 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,

				   struct bmp280_comp_press *comp,

				   s32 adc_press)

{

	int ret;

	s64 var1, var2, p;

	__le16 buf[BMP280_COMP_PRESS_REG_COUNT / 2];



	ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_PRESS_START,

			       buf, BMP280_COMP_PRESS_REG_COUNT);

	if (ret < 0) {

		dev_err(&data->client->dev,

			"failed to read pressure calibration parameters\n");

		return ret;

	}



	var1 = ((s64)data->t_fine) - 128000;

	var2 = var1 * var1 * (s64) comp->dig_p6;

	var2 = var2 + ((var1 * (s64) comp->dig_p5) << 17);

	var2 = var2 + (((s64) comp->dig_p4) << 35);

	var1 = ((var1 * var1 * (s64) comp->dig_p3) >> 8) +

		((var1 * (s64) comp->dig_p2) << 12);

	var1 = (((((s64) 1) << 47) + var1)) * ((s64) comp->dig_p1) >> 33;

	var2 = var1 * var1 * (s64)(s16)le16_to_cpu(buf[P6]);

	var2 = var2 + ((var1 * (s64)(s16)le16_to_cpu(buf[P5])) << 17);

	var2 = var2 + (((s64)(s16)le16_to_cpu(buf[P4])) << 35);

	var1 = ((var1 * var1 * (s64)(s16)le16_to_cpu(buf[P3])) >> 8) +

		((var1 * (s64)(s16)le16_to_cpu(buf[P2])) << 12);

	var1 = ((((s64)1) << 47) + var1) * ((s64)le16_to_cpu(buf[P1])) >> 33;



	if (var1 == 0)

		return 0;



	p = ((((s64)1048576 - adc_press) << 31) - var2) * 3125;

	p = div64_s64(p, var1);

	var1 = (((s64) comp->dig_p9) * (p >> 13) * (p >> 13)) >> 25;

	var2 = (((s64) comp->dig_p8) * p) >> 19;

	p = ((p + var1 + var2) >> 8) + (((s64) comp->dig_p7) << 4);

	var1 = (((s64)(s16)le16_to_cpu(buf[P9])) * (p >> 13) * (p >> 13)) >> 25;

	var2 = (((s64)(s16)le16_to_cpu(buf[P8])) * p) >> 19;

	p = ((p + var1 + var2) >> 8) + (((s64)(s16)le16_to_cpu(buf[P7])) << 4);



	return (u32) p;

}
@@ -253,11 +227,6 @@ static int bmp280_read_temp(struct bmp280_data *data, 
	int ret;

	__be32 tmp = 0;

	s32 adc_temp, comp_temp;

	struct bmp280_comp_temp comp;



	ret = bmp280_read_compensation_temp(data, &comp);

	if (ret < 0)

		return ret;



	ret = regmap_bulk_read(data->regmap, BMP280_REG_TEMP_MSB,

			       (u8 *) &tmp, 3);
@@ -267,7 +236,7 @@ static int bmp280_read_temp(struct bmp280_data *data, 
	}



	adc_temp = be32_to_cpu(tmp) >> 12;

	comp_temp = bmp280_compensate_temp(data, &comp, adc_temp);

	comp_temp = bmp280_compensate_temp(data, adc_temp);



	/*

	 * val might be NULL if we're called by the read_press routine,
@@ -288,11 +257,6 @@ static int bmp280_read_press(struct bmp280_data *data, 
	__be32 tmp = 0;

	s32 adc_press;

	u32 comp_press;

	struct bmp280_comp_press comp;



	ret = bmp280_read_compensation_press(data, &comp);

	if (ret < 0)

		return ret;



	/* Read and compensate temperature so we get a reading of t_fine. */

	ret = bmp280_read_temp(data, NULL);
@@ -307,7 +271,7 @@ static int bmp280_read_press(struct bmp280_data *data, 
	}



	adc_press = be32_to_cpu(tmp) >> 12;

	comp_press = bmp280_compensate_press(data, &comp, adc_press);

	comp_press = bmp280_compensate_press(data, adc_press);



	*val = comp_press;

	*val2 = 256000;