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Commit 4892688d authored by Daniel Baluta's avatar Daniel Baluta Committed by Jonathan Cameron
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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: default avatarDaniel Baluta <daniel.baluta@intel.com>
Signed-off-by: default avatarJonathan Cameron <jic23@kernel.org>
parent 6b90da4b

drivers/iio/magnetometer/mmc35240.c

+58 −4
Original line number Diff line number Diff line
@@ -58,6 +58,31 @@ 
#define MMC35240_WAIT_CHARGE_PUMP	50000	/* 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 {

	MMC35240_16_BITS_SLOW = 0, /* 100 Hz */

	MMC35240_16_BITS_FAST,     /* 200 Hz */
@@ -102,6 +127,10 @@ struct mmc35240_data { 
	struct mutex mutex;

	struct regmap *regmap;

	enum mmc35240_resolution res;



	/* OTP compensation */

	int axis_coef[3];

	int axis_scale[3];

};



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)

{

	int ret;

	int ret, y_convert, z_convert;

	unsigned int reg_id;

	u8 otp_data[6];



	ret = regmap_read(data->regmap, MMC35240_REG_ID, &reg_id);

	if (ret < 0) {
@@ -197,9 +227,30 @@ static int mmc35240_init(struct mmc35240_data *data) 
		return ret;



	/* 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,

				 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)
@@ -286,6 +337,9 @@ static int mmc35240_raw_to_mgauss(struct mmc35240_data *data, int index, 
	default:

		return -EINVAL;

	}

	/* apply OTP compensation */

	*val = (*val) * data->axis_coef[index] / data->axis_scale[index];



	return 0;

}