iio: magnetometer: yas530: Add temperature calculation to "chip_info" (2d6676ec) · Commits · git / linux-net

drivers/iio/magnetometer/yamaha-yas530.c

+54 −69

Original line number	Diff line number	Diff line
		@@ -79,7 +79,6 @@
		#define YAS530_DATA_BITS 12
		#define YAS530_DATA_CENTER BIT(YAS530_DATA_BITS - 1)
		#define YAS530_DATA_OVERFLOW (BIT(YAS530_DATA_BITS) - 1)
		#define YAS530_20DEGREES 182 /* Counts starting at -62 °C */

		#define YAS532_DEVICE_ID 0x02 /* YAS532/YAS533 (MS-3R/F) */
		#define YAS532_VERSION_AB 0 /* YAS532/533 AB (MS-3R/F AB) */
		@@ -91,7 +90,6 @@
		#define YAS532_DATA_BITS 13
		#define YAS532_DATA_CENTER BIT(YAS532_DATA_BITS - 1)
		#define YAS532_DATA_OVERFLOW (BIT(YAS532_DATA_BITS) - 1)
		#define YAS532_20DEGREES 390 /* Counts starting at -50 °C */

		/* Turn off device regulators etc after 5 seconds of inactivity */
		#define YAS5XX_AUTOSUSPEND_DELAY_MS 5000
		@@ -131,6 +129,14 @@ struct yas5xx;
		* @volatile_reg: device-specific volatile registers
		* @volatile_reg_qty: quantity of device-specific volatile registers
		* @scaling_val2: scaling value for IIO_CHAN_INFO_SCALE
		* @t_ref: number of counts at reference temperature 20 °C
		* @min_temp_x10: starting point of temperature counting in 1/10:s degrees Celsius
		*
		* The "t_ref" value for YAS532/533 is known from the Android driver.
		* For YAS530 it was approximately measured.
		*
		* The temperatures "min_temp_x10" are derived from the temperature resolutions
		* given in the data sheets.
		*/
		struct yas5xx_chip_info {
		unsigned int devid;
		@@ -139,6 +145,8 @@ struct yas5xx_chip_info {
		const int *volatile_reg;
		int volatile_reg_qty;
		u32 scaling_val2;
		u16 t_ref;
		s16 min_temp_x10;
		};

		/**
		@@ -337,6 +345,22 @@ static s32 yas530_linearize(struct yas5xx *yas5xx, u16 val, int axis)
		(yas5xx->hard_offsets[axis] - c->r[axis]) * coef;
		}

		static s32 yas5xx_calc_temperature(struct yas5xx *yas5xx, u16 t)
		{
		const struct yas5xx_chip_info *ci = yas5xx->chip_info;
		s32 to;
		u16 t_ref;
		s16 min_temp_x10;
		int ref_temp_x10;

		t_ref = ci->t_ref;
		min_temp_x10 = ci->min_temp_x10;
		ref_temp_x10 = 200;

		to = (min_temp_x10 + ((ref_temp_x10 - min_temp_x10) * t / t_ref)) * 100;
		return to;
		}

		/**
		* yas530_get_measure() - Measure a sample of all axis and process
		* @yas5xx: The device state
		@@ -352,7 +376,7 @@ static int yas530_get_measure(struct yas5xx yas5xx, s32 to, s32 xo, s32 yo,
		{
		const struct yas5xx_chip_info *ci = yas5xx->chip_info;
		struct yas5xx_calibration *c = &yas5xx->calibration;
		u16 t_ref, t, x, y1, y2;
		u16 t_ref, t_comp, t, x, y1, y2;
		/* These are signed x, signed y1 etc */
		s32 sx, sy1, sy2, sy, sz;
		int ret;
		@@ -367,46 +391,29 @@ static int yas530_get_measure(struct yas5xx yas5xx, s32 to, s32 xo, s32 yo,
		sy1 = yas530_linearize(yas5xx, y1, 1);
		sy2 = yas530_linearize(yas5xx, y2, 2);

		/* Set the temperature reference value (unit: counts) */
		switch (ci->devid) {
		case YAS530_DEVICE_ID:
		t_ref = YAS530_20DEGREES;
		break;
		case YAS532_DEVICE_ID:
		t_ref = YAS532_20DEGREES;
		break;
		default:
		dev_err(yas5xx->dev, "unknown device type\n");
		return -EINVAL;
		}

		/* Temperature compensation for x, y1, y2 respectively */
		if (ci->devid == YAS532_DEVICE_ID &&
		yas5xx->version == YAS532_VERSION_AC) {
		/*
		* YAS532 version AC uses the temperature deviation as a
		* multiplier.
		*
		* Cx * (t - t_ref)
		* x' = x - ----------------
		* 100
		* Set the temperature for compensation (unit: counts):
		* YAS532/YAS533 version AC uses the temperature deviation as a
		* multiplier. YAS530 and YAS532 version AB use solely the t value.
		*/
		sx = sx - (c->Cx * (t - t_ref)) / 100;
		sy1 = sy1 - (c->Cy1 * (t - t_ref)) / 100;
		sy2 = sy2 - (c->Cy2 * (t - t_ref)) / 100;
		t_ref = ci->t_ref;
		if (ci->devid == YAS532_DEVICE_ID &&
		yas5xx->version == YAS532_VERSION_AC) {
		t_comp = t - t_ref;
		} else {
		t_comp = t;
		}

		/*
		* YAS530 and YAS532 version AB use solely the t value as a
		* multiplier.
		* Temperature compensation for x, y1, y2 respectively:
		*
		* Cx * t
		* x' = x - ------
		* Cx * t_comp
		* x' = x - -----------
		* 100
		*/
		sx = sx - (c->Cx * t) / 100;
		sy1 = sy1 - (c->Cy1 * t) / 100;
		sy2 = sy2 - (c->Cy2 * t) / 100;
		}
		sx = sx - (c->Cx * t_comp) / 100;
		sy1 = sy1 - (c->Cy1 * t_comp) / 100;
		sy2 = sy2 - (c->Cy2 * t_comp) / 100;

		/*
		* Break y1 and y2 into y and z, y1 and y2 are apparently encoding
		@@ -415,36 +422,8 @@ static int yas530_get_measure(struct yas5xx yas5xx, s32 to, s32 xo, s32 yo,
		sy = sy1 - sy2;
		sz = -sy1 - sy2;

		/* Process temperature readout */
		switch (ci->devid) {
		case YAS530_DEVICE_ID:
		/*
		* Raw temperature value t is the number of counts starting
		* at -62 °C. Reference value t_ref is the number of counts
		* between -62 °C and 20 °C (82 °C range).
		*
		* Temperature in °C would be (82 / t_ref * t) - 62.
		*
		* Contrary to this, perform multiplication first and division
		* second due to calculating with integers.
		*
		* To get a nicer result, calculate with 1/10:s degrees Celsius
		* and finally multiply by 100 to return millidegrees Celsius.
		*/
		to = ((820 t / t_ref) - 620) * 100;
		break;
		case YAS532_DEVICE_ID:
		/*
		* Actually same procedure for YAS532 but the starting point is
		* at -50 °C. Reference value t_ref is the number of counts
		* between -50 °C and 20 °C (70 °C range).
		*/
		to = ((700 t / t_ref) - 500) * 100;
		break;
		default:
		dev_err(yas5xx->dev, "unknown device type\n");
		return -EINVAL;
		}
		/* Calculate temperature readout */
		*to = yas5xx_calc_temperature(yas5xx, t);

		/*
		* Calibrate [x,y,z] with some formulas like this:
		@@ -935,6 +914,8 @@ static const struct yas5xx_chip_info yas5xx_chip_info_tbl[] = {
		.volatile_reg = yas530_volatile_reg,
		.volatile_reg_qty = ARRAY_SIZE(yas530_volatile_reg),
		.scaling_val2 = 100000000, /* picotesla to Gauss */
		.t_ref = 182, /* counts */
		.min_temp_x10 = -620, /* 1/10:s degrees Celsius */
		},
		[yas532] = {
		.devid = YAS532_DEVICE_ID,
		@@ -943,6 +924,8 @@ static const struct yas5xx_chip_info yas5xx_chip_info_tbl[] = {
		.volatile_reg = yas530_volatile_reg,
		.volatile_reg_qty = ARRAY_SIZE(yas530_volatile_reg),
		.scaling_val2 = 100000, /* nanotesla to Gauss */
		.t_ref = 390, /* counts */
		.min_temp_x10 = -500, /* 1/10:s degrees Celsius */
		},
		[yas533] = {
		.devid = YAS532_DEVICE_ID,
		@@ -951,6 +934,8 @@ static const struct yas5xx_chip_info yas5xx_chip_info_tbl[] = {
		.volatile_reg = yas530_volatile_reg,
		.volatile_reg_qty = ARRAY_SIZE(yas530_volatile_reg),
		.scaling_val2 = 100000, /* nanotesla to Gauss */
		.t_ref = 390, /* counts */
		.min_temp_x10 = -500, /* 1/10:s degrees Celsius */
		},
		};