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: Vlad Dogaru <vlad.dogaru@intel.com> Acked-by: Hartmut Knaack <knaack.h@gmx.de> Signed-off-by: Jonathan Cameron <jic23@kernel.org>
This commit is contained in:
Vlad Dogaru
Jonathan Cameron
parent
8f6eb02596
commit
0f8994b18a
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@ -80,16 +80,12 @@ struct bmp280_data {
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s32 t_fine;
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};
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/* Compensation parameters. */
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struct bmp280_comp_temp {
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u16 dig_t1;
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s16 dig_t2, dig_t3;
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};
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struct bmp280_comp_press {
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u16 dig_p1;
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s16 dig_p2, dig_p3, dig_p4, dig_p5, dig_p6, dig_p7, dig_p8, dig_p9;
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};
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/*
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* These enums are used for indexing into the array of compensation
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* parameters.
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*/
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enum { T1, T2, T3 };
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enum { P1, P2, P3, P4, P5, P6, P7, P8, P9 };
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static const struct iio_chan_spec bmp280_channels[] = {
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{
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@ -141,10 +137,18 @@ static const struct regmap_config bmp280_regmap_config = {
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.volatile_reg = bmp280_is_volatile_reg,
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};
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static int bmp280_read_compensation_temp(struct bmp280_data *data,
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struct bmp280_comp_temp *comp)
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/*
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* Returns temperature in DegC, resolution is 0.01 DegC. Output value of
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* "5123" equals 51.23 DegC. t_fine carries fine temperature as global
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* value.
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*
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* Taken from datasheet, Section 3.11.3, "Compensation formula".
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*/
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static s32 bmp280_compensate_temp(struct bmp280_data *data,
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s32 adc_temp)
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{
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int ret;
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s32 var1, var2, t;
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__le16 buf[BMP280_COMP_TEMP_REG_COUNT / 2];
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ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_TEMP_START,
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@ -155,58 +159,19 @@ static int bmp280_read_compensation_temp(struct bmp280_data *data,
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return ret;
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}
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comp->dig_t1 = (u16) le16_to_cpu(buf[0]);
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comp->dig_t2 = (s16) le16_to_cpu(buf[1]);
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comp->dig_t3 = (s16) le16_to_cpu(buf[2]);
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return 0;
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}
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static int bmp280_read_compensation_press(struct bmp280_data *data,
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struct bmp280_comp_press *comp)
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{
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int ret;
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__le16 buf[BMP280_COMP_PRESS_REG_COUNT / 2];
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ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_PRESS_START,
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buf, BMP280_COMP_PRESS_REG_COUNT);
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if (ret < 0) {
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dev_err(&data->client->dev,
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"failed to read pressure calibration parameters\n");
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return ret;
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}
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comp->dig_p1 = (u16) le16_to_cpu(buf[0]);
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comp->dig_p2 = (s16) le16_to_cpu(buf[1]);
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comp->dig_p3 = (s16) le16_to_cpu(buf[2]);
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comp->dig_p4 = (s16) le16_to_cpu(buf[3]);
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comp->dig_p5 = (s16) le16_to_cpu(buf[4]);
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comp->dig_p6 = (s16) le16_to_cpu(buf[5]);
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comp->dig_p7 = (s16) le16_to_cpu(buf[6]);
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comp->dig_p8 = (s16) le16_to_cpu(buf[7]);
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comp->dig_p9 = (s16) le16_to_cpu(buf[8]);
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return 0;
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}
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/*
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* Returns temperature in DegC, resolution is 0.01 DegC. Output value of
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* "5123" equals 51.23 DegC. t_fine carries fine temperature as global
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* value.
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*
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* Taken from datasheet, Section 3.11.3, "Compensation formula".
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*/
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static s32 bmp280_compensate_temp(struct bmp280_data *data,
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struct bmp280_comp_temp *comp,
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s32 adc_temp)
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{
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s32 var1, var2, t;
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var1 = (((adc_temp >> 3) - ((s32) comp->dig_t1 << 1)) *
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((s32) comp->dig_t2)) >> 11;
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var2 = (((((adc_temp >> 4) - ((s32) comp->dig_t1)) *
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((adc_temp >> 4) - ((s32) comp->dig_t1))) >> 12) *
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((s32) comp->dig_t3)) >> 14;
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/*
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* The double casts are necessary because le16_to_cpu returns an
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* unsigned 16-bit value. Casting that value directly to a
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* signed 32-bit will not do proper sign extension.
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*
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* Conversely, T1 and P1 are unsigned values, so they can be
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* cast straight to the larger type.
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*/
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var1 = (((adc_temp >> 3) - ((s32)le16_to_cpu(buf[T1]) << 1)) *
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((s32)(s16)le16_to_cpu(buf[T2]))) >> 11;
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var2 = (((((adc_temp >> 4) - ((s32)le16_to_cpu(buf[T1]))) *
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((adc_temp >> 4) - ((s32)le16_to_cpu(buf[T1])))) >> 12) *
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((s32)(s16)le16_to_cpu(buf[T3]))) >> 14;
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data->t_fine = var1 + var2;
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t = (data->t_fine * 5 + 128) >> 8;
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@ -222,27 +187,36 @@ static s32 bmp280_compensate_temp(struct bmp280_data *data,
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* Taken from datasheet, Section 3.11.3, "Compensation formula".
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*/
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static u32 bmp280_compensate_press(struct bmp280_data *data,
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struct bmp280_comp_press *comp,
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s32 adc_press)
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{
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int ret;
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s64 var1, var2, p;
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__le16 buf[BMP280_COMP_PRESS_REG_COUNT / 2];
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var1 = ((s64) data->t_fine) - 128000;
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var2 = var1 * var1 * (s64) comp->dig_p6;
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var2 = var2 + ((var1 * (s64) comp->dig_p5) << 17);
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var2 = var2 + (((s64) comp->dig_p4) << 35);
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var1 = ((var1 * var1 * (s64) comp->dig_p3) >> 8) +
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((var1 * (s64) comp->dig_p2) << 12);
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var1 = (((((s64) 1) << 47) + var1)) * ((s64) comp->dig_p1) >> 33;
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ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_PRESS_START,
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buf, BMP280_COMP_PRESS_REG_COUNT);
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if (ret < 0) {
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dev_err(&data->client->dev,
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"failed to read pressure calibration parameters\n");
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return ret;
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}
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var1 = ((s64)data->t_fine) - 128000;
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var2 = var1 * var1 * (s64)(s16)le16_to_cpu(buf[P6]);
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var2 = var2 + ((var1 * (s64)(s16)le16_to_cpu(buf[P5])) << 17);
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var2 = var2 + (((s64)(s16)le16_to_cpu(buf[P4])) << 35);
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var1 = ((var1 * var1 * (s64)(s16)le16_to_cpu(buf[P3])) >> 8) +
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((var1 * (s64)(s16)le16_to_cpu(buf[P2])) << 12);
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var1 = ((((s64)1) << 47) + var1) * ((s64)le16_to_cpu(buf[P1])) >> 33;
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if (var1 == 0)
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return 0;
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p = ((((s64) 1048576 - adc_press) << 31) - var2) * 3125;
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p = ((((s64)1048576 - adc_press) << 31) - var2) * 3125;
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p = div64_s64(p, var1);
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var1 = (((s64) comp->dig_p9) * (p >> 13) * (p >> 13)) >> 25;
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var2 = (((s64) comp->dig_p8) * p) >> 19;
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p = ((p + var1 + var2) >> 8) + (((s64) comp->dig_p7) << 4);
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var1 = (((s64)(s16)le16_to_cpu(buf[P9])) * (p >> 13) * (p >> 13)) >> 25;
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var2 = (((s64)(s16)le16_to_cpu(buf[P8])) * p) >> 19;
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p = ((p + var1 + var2) >> 8) + (((s64)(s16)le16_to_cpu(buf[P7])) << 4);
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return (u32) p;
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}
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@ -253,11 +227,6 @@ static int bmp280_read_temp(struct bmp280_data *data,
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int ret;
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__be32 tmp = 0;
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s32 adc_temp, comp_temp;
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struct bmp280_comp_temp comp;
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ret = bmp280_read_compensation_temp(data, &comp);
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if (ret < 0)
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return ret;
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ret = regmap_bulk_read(data->regmap, BMP280_REG_TEMP_MSB,
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(u8 *) &tmp, 3);
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@ -267,7 +236,7 @@ static int bmp280_read_temp(struct bmp280_data *data,
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}
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adc_temp = be32_to_cpu(tmp) >> 12;
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comp_temp = bmp280_compensate_temp(data, &comp, adc_temp);
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comp_temp = bmp280_compensate_temp(data, adc_temp);
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/*
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* val might be NULL if we're called by the read_press routine,
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@ -288,11 +257,6 @@ static int bmp280_read_press(struct bmp280_data *data,
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__be32 tmp = 0;
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s32 adc_press;
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u32 comp_press;
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struct bmp280_comp_press comp;
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ret = bmp280_read_compensation_press(data, &comp);
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if (ret < 0)
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return ret;
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/* Read and compensate temperature so we get a reading of t_fine. */
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ret = bmp280_read_temp(data, NULL);
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@ -307,7 +271,7 @@ static int bmp280_read_press(struct bmp280_data *data,
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}
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adc_press = be32_to_cpu(tmp) >> 12;
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comp_press = bmp280_compensate_press(data, &comp, adc_press);
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comp_press = bmp280_compensate_press(data, adc_press);
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*val = comp_press;
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*val2 = 256000;
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