Message-Id: <1556721787-28500-1-git-send-email-eajames@linux.ibm.com>
Date:   Wed,  1 May 2019 09:43:07 -0500
From:   Eddie James <eajames@...ux.ibm.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-iio@...r.kernel.org, joel@....id.au, pmeerw@...erw.net,
        lars@...afoo.de, knaack.h@....de, jic23@...nel.org,
        Eddie James <eajames@...ux.ibm.com>
Subject: [PATCH] iio: dps310: Add pressure sensing capability

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@...ux.ibm.com>
---
 drivers/iio/pressure/dps310.c | 350 +++++++++++++++++++++++++++++++++++++-----
 1 file changed, 314 insertions(+), 36 deletions(-)

diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
index beb8b11..48cf83c 100644
--- a/drivers/iio/pressure/dps310.c
+++ b/drivers/iio/pressure/dps310.c
@@ -23,6 +23,7 @@
  */
 
 #include <linux/i2c.h>
+#include <linux/math64.h>
 #include <linux/module.h>
 #include <linux/regmap.h>
 
@@ -36,13 +37,15 @@
 #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)
 #define  DPS310_TMP_EXT		BIT(7)
 #define DPS310_MEAS_CFG		0x08
 #define  DPS310_MEAS_CTRL_BITS	GENMASK(2, 0)
-#define   DPS310_PRESSURE_EN	BIT(0)
+#define   DPS310_PRS_EN		BIT(0)
 #define   DPS310_TEMP_EN	BIT(1)
 #define   DPS310_BACKGROUND	BIT(2)
 #define  DPS310_PRS_RDY		BIT(4)
@@ -58,16 +61,17 @@
 #define DPS310_RESET		0x0c
 #define  DPS310_RESET_MAGIC	(BIT(0) | BIT(3))
 #define DPS310_COEF_BASE	0x10
+#define DPS310_NUM_COEF_REGS	0x12
 
 #define DPS310_PRS_BASE		DPS310_PRS_B0
 #define DPS310_TMP_BASE		DPS310_TMP_B0
 
-#define DPS310_TMP_RATE(_n)	ilog2(_n)
-#define DPS310_TMP_PRC(_n)	ilog2(_n)
+#define DPS310_CALC_RATE(_n)	ilog2(_n)
+#define DPS310_CALC_PRC(_n)	ilog2(_n)
 
 #define MCELSIUS_PER_CELSIUS	1000
 
-const int scale_factor[] = {
+static const int scale_factor[] = {
 	 524288,
 	1572864,
 	3670016,
@@ -83,6 +87,8 @@ struct dps310_data {
 	struct regmap *regmap;
 
 	s32 c0, c1;
+	s32 c00, c10, c20, c30, c01, c11, c21;
+	s32 pressure_raw;
 	s32 temp_raw;
 };
 
@@ -95,33 +101,80 @@ 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 TMP_RDY bit in MEAS_CFG */
-static int dps310_get_temp_coef(struct dps310_data *data)
+/* To be called after checking the COEF_RDY bit in MEAS_CFG */
+static int dps310_get_coefs(struct dps310_data *data)
 {
 	struct regmap *regmap = data->regmap;
-	uint8_t coef[3] = {0};
 	int r;
+	u8 coef[DPS310_NUM_COEF_REGS] = {0};
 	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
-	 */
-	r = regmap_bulk_read(regmap, DPS310_COEF_BASE, coef, 3);
+	/* Read all sensor calibration coefficients from the COEF registers. */
+	r = regmap_bulk_read(regmap, DPS310_COEF_BASE, coef,
+			     DPS310_NUM_COEF_REGS);
 	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;
@@ -137,6 +190,24 @@ 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;
@@ -147,13 +218,26 @@ static int dps310_set_temp_precision(struct dps310_data *data, int val)
 
 	shift_en = val >= 16 ? DPS310_TMP_SHIFT_EN : 0;
 	ret = regmap_write_bits(data->regmap, DPS310_CFG_REG,
-			DPS310_TMP_SHIFT_EN,
-			shift_en);
+				DPS310_TMP_SHIFT_EN, shift_en);
+
 	if (ret)
 		return ret;
 
 	return regmap_update_bits(data->regmap, DPS310_TMP_CFG,
-			DPS310_TMP_PRC_BITS, DPS310_TMP_PRC(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)
@@ -163,12 +247,23 @@ static int dps310_set_temp_samp_freq(struct dps310_data *data, int freq)
 	if (freq < 0 || freq > 128)
 		return -EINVAL;
 
-	val = DPS310_TMP_RATE(freq) << 4;
+	val = DPS310_CALC_RATE(freq) << 4;
 
 	return regmap_update_bits(data->regmap, DPS310_TMP_CFG,
 			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;
@@ -180,12 +275,53 @@ 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_factor[DPS310_CALC_PRC(r)];
+}
+
 static int dps310_get_temp_k(struct dps310_data *data)
 {
-	return scale_factor[DPS310_TMP_PRC(dps310_get_temp_precision(data))];
+	int r = dps310_get_temp_precision(data);
+
+	if (r < 0)
+		return r;
+
+	return scale_factor[DPS310_CALC_PRC(r)];
+}
+
+static int dps310_read_pres_raw(struct dps310_data *data)
+{
+	struct device *dev = &data->client->dev;
+	int r, ready;
+	u8 val[3];
+	s32 raw;
+
+	r = regmap_read(data->regmap, DPS310_MEAS_CFG, &ready);
+	if (r < 0)
+		return r;
+
+	if (!(ready & DPS310_PRS_RDY)) {
+		dev_dbg(dev, "pressure not ready\n");
+		return -EAGAIN;
+	}
+
+	r = regmap_bulk_read(data->regmap, DPS310_PRS_BASE, val, 3);
+	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(struct dps310_data *data)
+static int dps310_read_temp_raw(struct dps310_data *data)
 {
 	struct device *dev = &data->client->dev;
 	struct regmap *regmap = data->regmap;
@@ -251,26 +387,139 @@ 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;
+	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;
+
+	/* Ignore errors and use the latest temperature */
+	dps310_read_temp_raw(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;
 	}
-
-	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 +528,7 @@ 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;
 
@@ -302,8 +551,24 @@ static int dps310_read_raw(struct iio_dev *iio,
 	default:
 		return -EINVAL;
 	}
+}
 
-	return -EINVAL;
+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 = {
@@ -385,24 +650,37 @@ 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
 	 */
-	r = regmap_write(data->regmap, DPS310_TMP_CFG,
-			DPS310_TMP_EXT | DPS310_TMP_RATE(1) | DPS310_TMP_PRC(1));
+	r = regmap_write(data->regmap, DPS310_TMP_CFG, DPS310_TMP_EXT |
+		DPS310_CALC_RATE(1) | DPS310_CALC_PRC(1));
 	if (r < 0)
 		return r;
 
-	/* 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)
+		return r;
+
+	/* 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)
 		return r;
 
-	/* 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)
 		return r;
 
@@ -417,7 +695,7 @@ static int dps310_probe(struct i2c_client *client,
 	if (r < 0)
 		return r;
 
-	r = dps310_get_temp_coef(data);
+	r = dps310_get_coefs(data);
 	if (r < 0)
 		return r;
 
-- 
1.8.3.1

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