[PATCH v2 3/3] iio: dps310: Add pressure sensing capability

From: Eddie James
Date: Wed May 08 2019 - 15:36:53 EST

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The DPS310 supports measurement of pressure, so support that in the
driver. Use background measurement like the temperature sensing and
default to lowest precision and lowest measurement rate.

Signed-off-by: Eddie James <eajames@xxxxxxxxxxxxx>
---
drivers/iio/pressure/dps310.c | 331 +++++++++++++++++++++++++++++++++++++++---
1 file changed, 307 insertions(+), 24 deletions(-)

diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
index c42808e..a7ee28c 100644
--- a/drivers/iio/pressure/dps310.c
+++ b/drivers/iio/pressure/dps310.c
@@ -11,11 +11,11 @@
* c0 * 0.5 + c1 * T_raw / kT ÂC
*
* TODO:
- * - Pressure sensor readings
* - Optionally support the FIFO
*/

#include <linux/i2c.h>
+#include <linux/math64.h>
#include <linux/module.h>
#include <linux/regmap.h>

@@ -29,6 +29,8 @@
#define DPS310_TMP_B1 0x04
#define DPS310_TMP_B2 0x05
#define DPS310_PRS_CFG 0x06
+#define DPS310_PRS_RATE_BITS GENMASK(6, 4)
+#define DPS310_PRS_PRC_BITS GENMASK(3, 0)
#define DPS310_TMP_CFG 0x07
#define DPS310_TMP_RATE_BITS GENMASK(6, 4)
#define DPS310_TMP_PRC_BITS GENMASK(3, 0)
@@ -82,6 +84,8 @@ struct dps310_data {
struct regmap *regmap;

s32 c0, c1;
+ s32 c00, c10, c20, c30, c01, c11, c21;
+ s32 pressure_raw;
s32 temp_raw;
};

@@ -94,33 +98,79 @@ struct dps310_data {
BIT(IIO_CHAN_INFO_SAMP_FREQ) |
BIT(IIO_CHAN_INFO_RAW),
},
+ {
+ .type = IIO_PRESSURE,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_SCALE) |
+ BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO) |
+ BIT(IIO_CHAN_INFO_SAMP_FREQ) |
+ BIT(IIO_CHAN_INFO_RAW),
+ },
};

/* To be called after checking the COEF_RDY bit in MEAS_CFG */
-static int dps310_get_temp_coef(struct dps310_data *data)
+static int dps310_get_coefs(struct dps310_data *data)
{
struct regmap *regmap = data->regmap;
- u8 coef[3];
int r;
+ u8 coef[18];
u32 c0, c1;
+ u32 c00, c10, c20, c30, c01, c11, c21;

- /*
- * Read temperature calibration coefficients c0 and c1 from the
- * COEF register. The numbers are 12-bit 2's compliment numbers
- */
+ /* Read all sensor calibration coefficients from the COEF registers. */
r = regmap_bulk_read(regmap, DPS310_COEF_BASE, coef, sizeof(coef));
if (r < 0)
return r;

+ /*
+ * Calculate temperature calibration coefficients c0 and c1. The numbers
+ * are 12-bit 2's complement numbers.
+ */
c0 = (coef[0] << 4) | (coef[1] >> 4);
data->c0 = sign_extend32(c0, 11);

c1 = ((coef[1] & GENMASK(3, 0)) << 8) | coef[2];
data->c1 = sign_extend32(c1, 11);

+ /*
+ * Calculate pressure calibration coefficients. c00 and c10 are 20 bit
+ * 2's complement numbers, while the rest are 16 bit 2's complement
+ * numbers.
+ */
+ c00 = (coef[3] << 12) | (coef[4] << 4) | (coef[5] >> 4);
+ data->c00 = sign_extend32(c00, 19);
+
+ c10 = ((coef[5] & GENMASK(3, 0)) << 16) | (coef[6] << 8) | coef[7];
+ data->c10 = sign_extend32(c10, 19);
+
+ c01 = (coef[8] << 8) | coef[9];
+ data->c01 = sign_extend32(c01, 15);
+
+ c11 = (coef[10] << 8) | coef[11];
+ data->c11 = sign_extend32(c11, 15);
+
+ c20 = (coef[12] << 8) | coef[13];
+ data->c20 = sign_extend32(c20, 15);
+
+ c21 = (coef[14] << 8) | coef[15];
+ data->c21 = sign_extend32(c21, 15);
+
+ c30 = (coef[16] << 8) | coef[17];
+ data->c30 = sign_extend32(c30, 15);
+
return 0;
}

+static int dps310_get_pres_precision(struct dps310_data *data)
+{
+ int val, r;
+
+ r = regmap_read(data->regmap, DPS310_PRS_CFG, &val);
+ if (r < 0)
+ return r;
+
+ return BIT(val & GENMASK(2, 0));
+}
+
static int dps310_get_temp_precision(struct dps310_data *data)
{
int val, r;
@@ -136,6 +186,24 @@ static int dps310_get_temp_precision(struct dps310_data *data)
return BIT(val & GENMASK(2, 0));
}

+static int dps310_set_pres_precision(struct dps310_data *data, int val)
+{
+ int ret;
+ u8 shift_en;
+
+ if (val < 0 || val > 128)
+ return -EINVAL;
+
+ shift_en = val >= 16 ? DPS310_PRS_SHIFT_EN : 0;
+ ret = regmap_write_bits(data->regmap, DPS310_CFG_REG,
+ DPS310_PRS_SHIFT_EN, shift_en);
+ if (ret)
+ return ret;
+
+ return regmap_update_bits(data->regmap, DPS310_PRS_CFG,
+ DPS310_PRS_PRC_BITS, DPS310_CALC_PRC(val));
+}
+
static int dps310_set_temp_precision(struct dps310_data *data, int val)
{
int ret;
@@ -154,6 +222,19 @@ static int dps310_set_temp_precision(struct dps310_data *data, int val)
DPS310_TMP_PRC_BITS, DPS310_CALC_PRC(val));
}

+static int dps310_set_pres_samp_freq(struct dps310_data *data, int freq)
+{
+ u8 val;
+
+ if (freq < 0 || freq > 128)
+ return -EINVAL;
+
+ val = DPS310_CALC_RATE(freq) << 4;
+
+ return regmap_update_bits(data->regmap, DPS310_PRS_CFG,
+ DPS310_PRS_RATE_BITS, val);
+}
+
static int dps310_set_temp_samp_freq(struct dps310_data *data, int freq)
{
u8 val;
@@ -167,6 +248,17 @@ static int dps310_set_temp_samp_freq(struct dps310_data *data, int freq)
DPS310_TMP_RATE_BITS, val);
}

+static int dps310_get_pres_samp_freq(struct dps310_data *data)
+{
+ int val, r;
+
+ r = regmap_read(data->regmap, DPS310_PRS_CFG, &val);
+ if (r < 0)
+ return r;
+
+ return BIT((val & DPS310_PRS_RATE_BITS) >> 4);
+}
+
static int dps310_get_temp_samp_freq(struct dps310_data *data)
{
int val, r;
@@ -178,6 +270,16 @@ static int dps310_get_temp_samp_freq(struct dps310_data *data)
return BIT((val & DPS310_TMP_RATE_BITS) >> 4);
}

+static int dps310_get_pres_k(struct dps310_data *data)
+{
+ int r = dps310_get_pres_precision(data);
+
+ if (r < 0)
+ return r;
+
+ return scale_factors[DPS310_CALC_PRC(r)];
+}
+
static int dps310_get_temp_k(struct dps310_data *data)
{
int r = dps310_get_temp_precision(data);
@@ -188,21 +290,37 @@ static int dps310_get_temp_k(struct dps310_data *data)
return scale_factors[DPS310_CALC_PRC(r)];
}

-static int dps310_read_temp(struct dps310_data *data)
+static int dps310_read_pres_raw(struct dps310_data *data)
{
+ int r, ready;
u8 val[3];
s32 raw;
- int r, ready;
- int rate = dps310_get_temp_samp_freq(data);
+ int rate = dps310_get_pres_samp_freq(data);
int timeout = DPS310_POLL_TIMEOUT_US(rate);

/* Poll for sensor readiness; base the timeout upon the sample rate. */
r = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG, ready,
- ready & DPS310_TMP_RDY,
+ ready & DPS310_PRS_RDY,
DPS310_POLL_SLEEP_US(timeout), timeout);
+ if (r)
+ return r;
+
+ r = regmap_bulk_read(data->regmap, DPS310_PRS_BASE, val, sizeof(val));
if (r < 0)
return r;

+ raw = (val[0] << 16) | (val[1] << 8) | val[2];
+ data->pressure_raw = sign_extend32(raw, 23);
+
+ return 0;
+}
+
+static int dps310_read_temp_ready(struct dps310_data *data)
+{
+ int r;
+ u8 val[3];
+ s32 raw;
+
r = regmap_bulk_read(data->regmap, DPS310_TMP_BASE, val, sizeof(val));
if (r < 0)
return r;
@@ -213,6 +331,22 @@ static int dps310_read_temp(struct dps310_data *data)
return 0;
}

+static int dps310_read_temp_raw(struct dps310_data *data)
+{
+ int r, ready;
+ int rate = dps310_get_temp_samp_freq(data);
+ int timeout = DPS310_POLL_TIMEOUT_US(rate);
+
+ /* Poll for sensor readiness; base the timeout upon the sample rate. */
+ r = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG, ready,
+ ready & DPS310_TMP_RDY,
+ DPS310_POLL_SLEEP_US(timeout), timeout);
+ if (r < 0)
+ return r;
+
+ return dps310_read_temp_ready(data);
+}
+
static bool dps310_is_writeable_reg(struct device *dev, unsigned int reg)
{
switch (reg) {
@@ -253,24 +387,141 @@ static int dps310_write_raw(struct iio_dev *iio,
{
struct dps310_data *data = iio_priv(iio);

- if (chan->type != IIO_TEMP)
+ switch (mask) {
+ case IIO_CHAN_INFO_SAMP_FREQ:
+ switch (chan->type) {
+ case IIO_PRESSURE:
+ return dps310_set_pres_samp_freq(data, val);
+
+ case IIO_TEMP:
+ return dps310_set_temp_samp_freq(data, val);
+
+ default:
+ return -EINVAL;
+ }
+
+ case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+ switch (chan->type) {
+ case IIO_PRESSURE:
+ return dps310_set_pres_precision(data, val);
+
+ case IIO_TEMP:
+ return dps310_set_temp_precision(data, val);
+
+ default:
+ return -EINVAL;
+ }
+
+ default:
return -EINVAL;
+ }
+}
+
+static int dps310_calculate_pressure(struct dps310_data *data)
+{
+ int i, r, t_ready;
+ int kpi = dps310_get_pres_k(data);
+ int kti = dps310_get_temp_k(data);
+ s64 rem = 0ULL;
+ s64 pressure = 0ULL;
+ s64 p;
+ s64 t;
+ s64 denoms[7];
+ s64 nums[7];
+ s64 rems[7];
+ s64 kp;
+ s64 kt;
+
+ if (kpi < 0)
+ return kpi;
+
+ if (kti < 0)
+ return kti;
+
+ kp = (s64)kpi;
+ kt = (s64)kti;
+
+ /* Refresh temp if it's ready, otherwise just use the latest value */
+ r = regmap_read(data->regmap, DPS310_MEAS_CFG, &t_ready);
+ if (r >= 0 && t_ready & DPS310_TMP_RDY)
+ dps310_read_temp_ready(data);
+
+ p = (s64)data->pressure_raw;
+ t = (s64)data->temp_raw;
+
+ /* Section 4.9.1 of the DPS310 spec; algebra'd to avoid underflow */
+ nums[0] = (s64)data->c00;
+ denoms[0] = 1LL;
+ nums[1] = p * (s64)data->c10;
+ denoms[1] = kp;
+ nums[2] = p * p * (s64)data->c20;
+ denoms[2] = kp * kp;
+ nums[3] = p * p * p * (s64)data->c30;
+ denoms[3] = kp * kp * kp;
+ nums[4] = t * (s64)data->c01;
+ denoms[4] = kt;
+ nums[5] = t * p * (s64)data->c11;
+ denoms[5] = kp * kt;
+ nums[6] = t * p * p * (s64)data->c21;
+ denoms[6] = kp * kp * kt;
+
+ /* Kernel lacks a div64_s64_rem function; denoms are all positive */
+ for (i = 0; i < 7; ++i) {
+ u64 rem;
+
+ if (nums[i] < 0LL) {
+ pressure -= div64_u64_rem(-nums[i], denoms[i], &rem);
+ rems[i] = -rem;
+ } else {
+ pressure += div64_u64_rem(nums[i], denoms[i], &rem);
+ rems[i] = (s64)rem;
+ }
+ }
+
+ /* Increase precision and calculate the remainder sum */
+ for (i = 0; i < 7; ++i)
+ rem += div64_s64((s64)rems[i] * 1000000000LL, denoms[i]);
+
+ pressure += div_s64(rem, 1000000000LL);
+
+ return (int)pressure;
+}
+
+static int dps310_read_pressure(struct dps310_data *data, int *val, int *val2,
+ long mask)
+{
+ int ret;

switch (mask) {
case IIO_CHAN_INFO_SAMP_FREQ:
- return dps310_set_temp_samp_freq(data, val);
+ *val = dps310_get_pres_samp_freq(data);
+ return IIO_VAL_INT;
+
+ case IIO_CHAN_INFO_RAW:
+ ret = dps310_read_pres_raw(data);
+ if (ret)
+ return ret;
+
+ *val = dps310_calculate_pressure(data);
+ return IIO_VAL_INT;
+
+ case IIO_CHAN_INFO_SCALE:
+ *val = 1;
+ *val2 = 1000; /* Convert Pa to KPa per IIO ABI */
+ return IIO_VAL_FRACTIONAL;
+
case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
- return dps310_set_temp_precision(data, val);
+ *val = dps310_get_pres_precision(data);
+ return IIO_VAL_INT;
+
default:
return -EINVAL;
}
}

-static int dps310_read_raw(struct iio_dev *iio,
- struct iio_chan_spec const *chan,
- int *val, int *val2, long mask)
+static int dps310_read_temp(struct dps310_data *data, int *val, int *val2,
+ long mask)
{
- struct dps310_data *data = iio_priv(iio);
int ret;

switch (mask) {
@@ -279,7 +530,7 @@ static int dps310_read_raw(struct iio_dev *iio,
return IIO_VAL_INT;

case IIO_CHAN_INFO_RAW:
- ret = dps310_read_temp(data);
+ ret = dps310_read_temp_raw(data);
if (ret)
return ret;

@@ -312,6 +563,24 @@ static int dps310_read_raw(struct iio_dev *iio,
}
}

+static int dps310_read_raw(struct iio_dev *iio,
+ struct iio_chan_spec const *chan,
+ int *val, int *val2, long mask)
+{
+ struct dps310_data *data = iio_priv(iio);
+
+ switch (chan->type) {
+ case IIO_PRESSURE:
+ return dps310_read_pressure(data, val, val2, mask);
+
+ case IIO_TEMP:
+ return dps310_read_temp(data, val, val2, mask);
+
+ default:
+ return -EINVAL;
+ }
+}
+
static const struct regmap_config dps310_regmap_config = {
.reg_bits = 8,
.val_bits = 8,
@@ -393,6 +662,13 @@ static int dps310_probe(struct i2c_client *client,
return PTR_ERR(data->regmap);

/*
+ * Set up pressure sensor in single sample, one measurement per second
+ * mode
+ */
+ r = regmap_write(data->regmap, DPS310_PRS_CFG,
+ DPS310_CALC_RATE(1) | DPS310_CALC_PRC(1));
+
+ /*
* Set up external (MEMS) temperature sensor in single sample, one
* measurement per second mode
*/
@@ -402,16 +678,23 @@ static int dps310_probe(struct i2c_client *client,
if (r < 0)
goto err;

- /* Temp shift is disabled when PRC <= 8 */
+ /* Temp and pressure shifts are disabled when PRC <= 8 */
r = regmap_write_bits(data->regmap, DPS310_CFG_REG,
- DPS310_TMP_SHIFT_EN, 0);
+ DPS310_TMP_SHIFT_EN | DPS310_PRS_SHIFT_EN, 0);
+ if (r < 0)
+ goto err;
+
+ /* MEAS_CFG doesn't seem to update unless first written with 0 */
+ r = regmap_write_bits(data->regmap, DPS310_MEAS_CFG,
+ DPS310_MEAS_CTRL_BITS, 0);
if (r < 0)
goto err;

- /* Turn on temperature measurement in the background */
+ /* Turn on temperature and pressure measurement in the background */
r = regmap_write_bits(data->regmap, DPS310_MEAS_CFG,
DPS310_MEAS_CTRL_BITS,
- DPS310_TEMP_EN | DPS310_BACKGROUND);
+ DPS310_PRS_EN | DPS310_TEMP_EN |
+ DPS310_BACKGROUND);
if (r < 0)
goto err;

@@ -424,7 +707,7 @@ static int dps310_probe(struct i2c_client *client,
if (r < 0)
goto err;

- r = dps310_get_temp_coef(data);
+ r = dps310_get_coefs(data);
if (r < 0)
goto err;

--
1.8.3.1

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Next in thread: Jonathan Cameron: "Re: [PATCH v2 3/3] iio: dps310: Add pressure sensing capability"
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