Add temperature calculation to the "chip_info" structure to ease the handling
of different YAS variants.
Signed-off-by: Jakob Hauser <jahau@xxxxxxxxxxxxxx>
---
drivers/iio/magnetometer/yamaha-yas530.c | 140 ++++++++++++-----------
1 file changed, 71 insertions(+), 69 deletions(-)
diff --git a/drivers/iio/magnetometer/yamaha-yas530.c b/drivers/iio/magnetometer/yamaha-yas530.c
index 262a36c31616..780c7f4d1eff 100644
--- a/drivers/iio/magnetometer/yamaha-yas530.c
+++ b/drivers/iio/magnetometer/yamaha-yas530.c
@@ -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
@@ -119,6 +117,31 @@ static const int yas530_volatile_reg[] = {
YAS530_MEASURE,
};
+/*
+ * t_ref_counts is the number of counts at reference temperature.
+ *
+ * The temperature value at YAS magnetometers is a number of counts. The
+ * values in t_ref_counts[] are the counts at the reference temperature
+ * of 20 °C.
+ *
+ * For YAS532/533, this value is known from the Android driver. For YAS530,
+ * it was approximately measured.
+ */
+static const u16 t_ref_counts[] = { 182, 390, 390 };
+
+/*
+ * min_temp_celsius_x10 is the starting point of temperature counting
+ * in 1/10:s degrees Celsius.
+ *
+ * The array min_temp_celsius_x10[] contains the temperatures where the
+ * temperature value count is 0. The values are in 1/10:s degrees Celsius
+ * to ease the further temperature calculation.
+ *
+ * These temperatures are derived from the temperature resolutions given
+ * in the data sheets.
+ */
+static const s16 min_temp_celsius_x10[] = { -620, -500, -500 };
+
struct yas5xx_calibration {
/* Linearization calibration x, y1, y2 */
s32 r[3];
@@ -143,6 +166,8 @@ 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
+ * @min_temp_x10: starting point of temperature counting in 1/10:s degrees Celsius
*/
struct yas5xx_chip_info {
unsigned int devid;
@@ -151,6 +176,8 @@ struct yas5xx_chip_info {
const int *volatile_reg;
int volatile_reg_qty;
u32 scaling_val2;
+ u16 t_ref;
+ s16 min_temp_x10;
};
/**
@@ -349,6 +376,20 @@ 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)
+{
+ s32 to;
+ u16 t_ref;
+ int min_temp_x10, ref_temp_x10;
+
+ t_ref = yas5xx->chip_info->t_ref;
+ min_temp_x10 = yas5xx->chip_info->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
@@ -363,7 +404,7 @@ static s32 yas530_linearize(struct yas5xx *yas5xx, u16 val, int axis)
static int yas530_get_measure(struct yas5xx *yas5xx, s32 *to, s32 *xo, s32 *yo, s32 *zo)
{
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;
@@ -378,47 +419,30 @@ 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 (yas5xx->chip_info->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 */
+ /*
+ * 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.
+ */
+ t_ref = yas5xx->chip_info->t_ref;
if (yas5xx->chip_info->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
- */
- 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_comp = t - t_ref;
} else {
- /*
- * YAS530 and YAS532 version AB use solely the t value as a
- * multiplier.
- *
- * Cx * t
- * x' = x - ------
- * 100
- */
- sx = sx - (c->Cx * t) / 100;
- sy1 = sy1 - (c->Cy1 * t) / 100;
- sy2 = sy2 - (c->Cy2 * t) / 100;
+ t_comp = t;
}
+ /*
+ * Temperature compensation for x, y1, y2 respectively:
+ *
+ * Cx * t_comp
+ * x' = x - -----------
+ * 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
* y and z.
@@ -426,36 +450,8 @@ static int yas530_get_measure(struct yas5xx *yas5xx, s32 *to, s32 *xo, s32 *yo,
sy = sy1 - sy2;
sz = -sy1 - sy2;
- /* Process temperature readout */
- switch (yas5xx->chip_info->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:
@@ -943,6 +939,8 @@ 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 = t_ref_counts[yas530],
+ .min_temp_x10 = min_temp_celsius_x10[yas530],
},
[yas532] = {
.devid = YAS532_DEVICE_ID,
@@ -951,6 +949,8 @@ 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 = t_ref_counts[yas532],
+ .min_temp_x10 = min_temp_celsius_x10[yas532],
},
[yas533] = {
.devid = YAS532_DEVICE_ID,
@@ -959,6 +959,8 @@ 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 = t_ref_counts[yas533],
+ .min_temp_x10 = min_temp_celsius_x10[yas533],
},
};
--
2.35.1
