On Mon, Aug 8, 2022 at 1:07 AM Jakob Hauser <jahau@xxxxxxxxxxxxxx> wrote:
>
> Add temperature calculation to the "chip_info" structure to ease the handling
> of different YAS variants.
Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
> 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
>
--
With Best Regards,
Andy Shevchenko
