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iio: magnetometer: mmc35240: Add compensation for raw values 

This patch adds compensation formula to raw readings, borrowed
from Memsic's input driver.

Signed-off-by: Daniel Baluta <daniel.baluta@intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
This commit is contained in:
Daniel Baluta 2015-06-05 14:03:15 +03:00 committed by Jonathan Cameron
parent 6b90da4b58
commit 4892688d70
1 changed files with 58 additions and 4 deletions
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62
drivers/iio/magnetometer/mmc35240.c
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@ -58,6 +58,31 @@
#define MMC35240_WAIT_CHARGE_PUMP 50000 /* us */ #define MMC35240_WAIT_CHARGE_PUMP 50000 /* us */
#define MMC53240_WAIT_SET_RESET 1000 /* us */ #define MMC53240_WAIT_SET_RESET 1000 /* us */
/*
* Memsic OTP process code piece is put here for reference:
*
* #define OTP_CONVERT(REG) ((float)((REG) >=32 ? (32 - (REG)) : (REG)) * 0.006
* 1) For X axis, the COEFFICIENT is always 1.
* 2) For Y axis, the COEFFICIENT is as below:
* f_OTP_matrix[4] = OTP_CONVERT(((reg_data[1] & 0x03) << 4) |
* (reg_data[2] >> 4)) + 1.0;
* 3) For Z axis, the COEFFICIENT is as below:
* f_OTP_matrix[8] = (OTP_CONVERT(reg_data[3] & 0x3f) + 1) * 1.35;
* We implemented the OTP logic into driver.
*/
/* scale = 1000 here for Y otp */
#define MMC35240_OTP_CONVERT_Y(REG) (((REG) >= 32 ? (32 - (REG)) : (REG)) * 6)
/* 0.6 * 1.35 = 0.81, scale 10000 for Z otp */
#define MMC35240_OTP_CONVERT_Z(REG) (((REG) >= 32 ? (32 - (REG)) : (REG)) * 81)
#define MMC35240_X_COEFF(x) (x)
#define MMC35240_Y_COEFF(y) (y + 1000)
#define MMC35240_Z_COEFF(z) (z + 13500)
#define MMC35240_OTP_START_ADDR 0x1B
enum mmc35240_resolution { enum mmc35240_resolution {
MMC35240_16_BITS_SLOW = 0, /* 100 Hz */ MMC35240_16_BITS_SLOW = 0, /* 100 Hz */
MMC35240_16_BITS_FAST, /* 200 Hz */ MMC35240_16_BITS_FAST, /* 200 Hz */
@ -102,6 +127,10 @@ struct mmc35240_data {
struct mutex mutex; struct mutex mutex;
struct regmap *regmap; struct regmap *regmap;
enum mmc35240_resolution res; enum mmc35240_resolution res;
/* OTP compensation */
int axis_coef[3];
int axis_scale[3];
}; };
static const int mmc35240_samp_freq[] = {100, 200, 333, 666}; static const int mmc35240_samp_freq[] = {100, 200, 333, 666};
@ -172,8 +201,9 @@ static int mmc35240_hw_set(struct mmc35240_data *data, bool set)
static int mmc35240_init(struct mmc35240_data *data) static int mmc35240_init(struct mmc35240_data *data)
{ {
int ret; int ret, y_convert, z_convert;
unsigned int reg_id; unsigned int reg_id;
u8 otp_data[6];
ret = regmap_read(data->regmap, MMC35240_REG_ID, &reg_id); ret = regmap_read(data->regmap, MMC35240_REG_ID, &reg_id);
if (ret < 0) { if (ret < 0) {
@ -197,9 +227,30 @@ static int mmc35240_init(struct mmc35240_data *data)
return ret; return ret;
/* set default sampling frequency */ /* set default sampling frequency */
return regmap_update_bits(data->regmap, MMC35240_REG_CTRL1, ret = regmap_update_bits(data->regmap, MMC35240_REG_CTRL1,
MMC35240_CTRL1_BW_MASK, MMC35240_CTRL1_BW_MASK,
data->res << MMC35240_CTRL1_BW_SHIFT); data->res << MMC35240_CTRL1_BW_SHIFT);
if (ret < 0)
return ret;
ret = regmap_bulk_read(data->regmap, MMC35240_OTP_START_ADDR,
(u8 *)otp_data, sizeof(otp_data));
if (ret < 0)
return ret;
y_convert = MMC35240_OTP_CONVERT_Y(((otp_data[1] & 0x03) << 4) |
(otp_data[2] >> 4));
z_convert = MMC35240_OTP_CONVERT_Z(otp_data[3] & 0x3f);
data->axis_coef[0] = MMC35240_X_COEFF(1);
data->axis_coef[1] = MMC35240_Y_COEFF(y_convert);
data->axis_coef[2] = MMC35240_Z_COEFF(z_convert);
data->axis_scale[0] = 1;
data->axis_scale[1] = 1000;
data->axis_scale[2] = 10000;
return 0;
} }
static int mmc35240_take_measurement(struct mmc35240_data *data) static int mmc35240_take_measurement(struct mmc35240_data *data)
@ -286,6 +337,9 @@ static int mmc35240_raw_to_mgauss(struct mmc35240_data *data, int index,
default: default:
return -EINVAL; return -EINVAL;
} }
/* apply OTP compensation */
*val = (*val) * data->axis_coef[index] / data->axis_scale[index];
return 0; return 0;
} }