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Date:   Sun, 26 May 2019 18:35:45 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Eddie James <eajames@...ux.ibm.com>
Cc:     linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        joel@....id.au, lars@...afoo.de, knaack.h@....de
Subject: Re: [PATCH v4 3/3] iio: dps310: Add pressure sensing capability

On Mon, 20 May 2019 21:13:34 -0500
Eddie James <eajames@...ux.ibm.com> wrote:

> 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>
> Acked-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Applied to the togreg branch of iio.git and pushed out as testing for
the autobuilders to play with it.

Thanks,

Jonathan

> ---
>  drivers/iio/pressure/dps310.c | 363 +++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 337 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
> index a093e3a..2c1943b 100644
> --- a/drivers/iio/pressure/dps310.c
> +++ b/drivers/iio/pressure/dps310.c
> @@ -11,11 +11,12 @@
>   *   c0 * 0.5 + c1 * T_raw / kT °C
>   *
>   * TODO:
> - *  - Pressure sensor readings
>   *  - Optionally support the FIFO
>   */
>  
>  #include <linux/i2c.h>
> +#include <linux/limits.h>
> +#include <linux/math64.h>
>  #include <linux/module.h>
>  #include <linux/regmap.h>
>  
> @@ -31,6 +32,8 @@
>  #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)
> @@ -83,6 +86,8 @@ struct dps310_data {
>  	struct mutex lock;	/* Lock for sequential HW access functions */
>  
>  	s32 c0, c1;
> +	s32 c00, c10, c20, c30, c01, c11, c21;
> +	s32 pressure_raw;
>  	s32 temp_raw;
>  };
>  
> @@ -93,33 +98,79 @@ struct dps310_data {
>  			BIT(IIO_CHAN_INFO_SAMP_FREQ) |
>  			BIT(IIO_CHAN_INFO_PROCESSED),
>  	},
> +	{
> +		.type = IIO_PRESSURE,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO) |
> +			BIT(IIO_CHAN_INFO_SAMP_FREQ) |
> +			BIT(IIO_CHAN_INFO_PROCESSED),
> +	},
>  };
>  
>  /* 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)
>  {
>  	int rc;
> -	u8 coef[3];
> +	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. */
>  	rc = regmap_bulk_read(data->regmap, DPS310_COEF_BASE, coef,
>  			      sizeof(coef));
>  	if (rc < 0)
>  		return rc;
>  
> +	/*
> +	 * 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 rc;
> +	int val;
> +
> +	rc = regmap_read(data->regmap, DPS310_PRS_CFG, &val);
> +	if (rc < 0)
> +		return rc;
> +
> +	return BIT(val & GENMASK(2, 0));
> +}
> +
>  static int dps310_get_temp_precision(struct dps310_data *data)
>  {
>  	int rc;
> @@ -137,6 +188,25 @@ static int dps310_get_temp_precision(struct dps310_data *data)
>  }
>  
>  /* Called with lock held */
> +static int dps310_set_pres_precision(struct dps310_data *data, int val)
> +{
> +	int rc;
> +	u8 shift_en;
> +
> +	if (val < 0 || val > 128)
> +		return -EINVAL;
> +
> +	shift_en = val >= 16 ? DPS310_PRS_SHIFT_EN : 0;
> +	rc = regmap_write_bits(data->regmap, DPS310_CFG_REG,
> +			       DPS310_PRS_SHIFT_EN, shift_en);
> +	if (rc)
> +		return rc;
> +
> +	return regmap_update_bits(data->regmap, DPS310_PRS_CFG,
> +				  DPS310_PRS_PRC_BITS, ilog2(val));
> +}
> +
> +/* Called with lock held */
>  static int dps310_set_temp_precision(struct dps310_data *data, int val)
>  {
>  	int rc;
> @@ -156,6 +226,20 @@ static int dps310_set_temp_precision(struct dps310_data *data, int val)
>  }
>  
>  /* Called with lock held */
> +static int dps310_set_pres_samp_freq(struct dps310_data *data, int freq)
> +{
> +	u8 val;
> +
> +	if (freq < 0 || freq > 128)
> +		return -EINVAL;
> +
> +	val = ilog2(freq) << 4;
> +
> +	return regmap_update_bits(data->regmap, DPS310_PRS_CFG,
> +				  DPS310_PRS_RATE_BITS, val);
> +}
> +
> +/* Called with lock held */
>  static int dps310_set_temp_samp_freq(struct dps310_data *data, int freq)
>  {
>  	u8 val;
> @@ -169,6 +253,18 @@ 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 rc;
> +	int val;
> +
> +	rc = regmap_read(data->regmap, DPS310_PRS_CFG, &val);
> +	if (rc < 0)
> +		return rc;
> +
> +	return BIT((val & DPS310_PRS_RATE_BITS) >> 4);
> +}
> +
>  static int dps310_get_temp_samp_freq(struct dps310_data *data)
>  {
>  	int rc;
> @@ -181,6 +277,16 @@ 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 rc = dps310_get_pres_precision(data);
> +
> +	if (rc < 0)
> +		return rc;
> +
> +	return scale_factors[ilog2(rc)];
> +}
> +
>  static int dps310_get_temp_k(struct dps310_data *data)
>  {
>  	int rc = dps310_get_temp_precision(data);
> @@ -191,7 +297,7 @@ static int dps310_get_temp_k(struct dps310_data *data)
>  	return scale_factors[ilog2(rc)];
>  }
>  
> -static int dps310_read_temp(struct dps310_data *data)
> +static int dps310_read_pres_raw(struct dps310_data *data)
>  {
>  	int rc;
>  	int rate;
> @@ -203,23 +309,67 @@ static int dps310_read_temp(struct dps310_data *data)
>  	if (mutex_lock_interruptible(&data->lock))
>  		return -EINTR;
>  
> -	rate = dps310_get_temp_samp_freq(data);
> +	rate = dps310_get_pres_samp_freq(data);
>  	timeout = DPS310_POLL_TIMEOUT_US(rate);
>  
>  	/* Poll for sensor readiness; base the timeout upon the sample rate. */
>  	rc = 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 (rc)
> +		goto done;
> +
> +	rc = regmap_bulk_read(data->regmap, DPS310_PRS_BASE, val, sizeof(val));
>  	if (rc < 0)
>  		goto done;
>  
> +	raw = (val[0] << 16) | (val[1] << 8) | val[2];
> +	data->pressure_raw = sign_extend32(raw, 23);
> +
> +done:
> +	mutex_unlock(&data->lock);
> +	return rc;
> +}
> +
> +/* Called with lock held */
> +static int dps310_read_temp_ready(struct dps310_data *data)
> +{
> +	int rc;
> +	u8 val[3];
> +	s32 raw;
> +
>  	rc = regmap_bulk_read(data->regmap, DPS310_TMP_BASE, val, sizeof(val));
>  	if (rc < 0)
> -		goto done;
> +		return rc;
>  
>  	raw = (val[0] << 16) | (val[1] << 8) | val[2];
>  	data->temp_raw = sign_extend32(raw, 23);
>  
> +	return 0;
> +}
> +
> +static int dps310_read_temp_raw(struct dps310_data *data)
> +{
> +	int rc;
> +	int rate;
> +	int ready;
> +	int timeout;
> +
> +	if (mutex_lock_interruptible(&data->lock))
> +		return -EINTR;
> +
> +	rate = dps310_get_temp_samp_freq(data);
> +	timeout = DPS310_POLL_TIMEOUT_US(rate);
> +
> +	/* Poll for sensor readiness; base the timeout upon the sample rate. */
> +	rc = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG, ready,
> +				      ready & DPS310_TMP_RDY,
> +				      DPS310_POLL_SLEEP_US(timeout), timeout);
> +	if (rc < 0)
> +		goto done;
> +
> +	rc = dps310_read_temp_ready(data);
> +
>  done:
>  	mutex_unlock(&data->lock);
>  	return rc;
> @@ -267,19 +417,40 @@ static int dps310_write_raw(struct iio_dev *iio,
>  	int rc;
>  	struct dps310_data *data = iio_priv(iio);
>  
> -	if (chan->type != IIO_TEMP)
> -		return -EINVAL;
> -
>  	if (mutex_lock_interruptible(&data->lock))
>  		return -EINTR;
>  
>  	switch (mask) {
>  	case IIO_CHAN_INFO_SAMP_FREQ:
> -		rc = dps310_set_temp_samp_freq(data, val);
> +		switch (chan->type) {
> +		case IIO_PRESSURE:
> +			rc = dps310_set_pres_samp_freq(data, val);
> +			break;
> +
> +		case IIO_TEMP:
> +			rc = dps310_set_temp_samp_freq(data, val);
> +			break;
> +
> +		default:
> +			rc = -EINVAL;
> +			break;
> +		}
>  		break;
>  
>  	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
> -		rc = dps310_set_temp_precision(data, val);
> +		switch (chan->type) {
> +		case IIO_PRESSURE:
> +			rc = dps310_set_pres_precision(data, val);
> +			break;
> +
> +		case IIO_TEMP:
> +			rc = dps310_set_temp_precision(data, val);
> +			break;
> +
> +		default:
> +			rc = -EINVAL;
> +			break;
> +		}
>  		break;
>  
>  	default:
> @@ -291,6 +462,124 @@ static int dps310_write_raw(struct iio_dev *iio,
>  	return rc;
>  }
>  
> +static int dps310_calculate_pressure(struct dps310_data *data)
> +{
> +	int i;
> +	int rc;
> +	int 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 */
> +	if (mutex_trylock(&data->lock)) {
> +		rc = regmap_read(data->regmap, DPS310_MEAS_CFG, &t_ready);
> +		if (rc >= 0 && t_ready & DPS310_TMP_RDY)
> +			dps310_read_temp_ready(data);
> +
> +		mutex_unlock(&data->lock);
> +	}
> +
> +	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 irem;
> +
> +		if (nums[i] < 0LL) {
> +			pressure -= div64_u64_rem(-nums[i], denoms[i], &irem);
> +			rems[i] = -irem;
> +		} else {
> +			pressure += div64_u64_rem(nums[i], denoms[i], &irem);
> +			rems[i] = (s64)irem;
> +		}
> +	}
> +
> +	/* 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);
> +	if (pressure < 0LL)
> +		return -ERANGE;
> +
> +	return (int)min_t(s64, pressure, INT_MAX);
> +}
> +
> +static int dps310_read_pressure(struct dps310_data *data, int *val, int *val2,
> +				long mask)
> +{
> +	int rc;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_SAMP_FREQ:
> +		rc = dps310_get_pres_samp_freq(data);
> +		if (rc < 0)
> +			return rc;
> +
> +		*val = rc;
> +		return IIO_VAL_INT;
> +
> +	case IIO_CHAN_INFO_PROCESSED:
> +		rc = dps310_read_pres_raw(data);
> +		if (rc)
> +			return rc;
> +
> +		rc = dps310_calculate_pressure(data);
> +		if (rc < 0)
> +			return rc;
> +
> +		*val = rc;
> +		*val2 = 1000; /* Convert Pa to KPa per IIO ABI */
> +		return IIO_VAL_FRACTIONAL;
> +
> +	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
> +		rc = dps310_get_pres_precision(data);
> +		if (rc < 0)
> +			return rc;
> +
> +		*val = rc;
> +		return IIO_VAL_INT;
> +
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
>  static int dps310_calculate_temp(struct dps310_data *data)
>  {
>  	s64 c0;
> @@ -310,11 +599,9 @@ static int dps310_calculate_temp(struct dps310_data *data)
>  	return (int)div_s64(t * 1000LL, kt);
>  }
>  
> -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 rc;
>  
>  	switch (mask) {
> @@ -327,7 +614,7 @@ static int dps310_read_raw(struct iio_dev *iio,
>  		return IIO_VAL_INT;
>  
>  	case IIO_CHAN_INFO_PROCESSED:
> -		rc = dps310_read_temp(data);
> +		rc = dps310_read_temp_raw(data);
>  		if (rc)
>  			return rc;
>  
> @@ -351,6 +638,24 @@ 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 void dps310_reset(void *action_data)
>  {
>  	struct dps310_data *data = action_data;
> @@ -444,6 +749,12 @@ static int dps310_probe(struct i2c_client *client,
>  		return rc;
>  
>  	/*
> +	 * Set up pressure sensor in single sample, one measurement per second
> +	 * mode
> +	 */
> +	rc = regmap_write(data->regmap, DPS310_PRS_CFG, 0);
> +
> +	/*
>  	 * Set up external (MEMS) temperature sensor in single sample, one
>  	 * measurement per second mode
>  	 */
> @@ -451,9 +762,9 @@ static int dps310_probe(struct i2c_client *client,
>  	if (rc < 0)
>  		return rc;
>  
> -	/* Temp shift is disabled when PRC <= 8 */
> +	/* Temp and pressure shifts are disabled when PRC <= 8 */
>  	rc = regmap_write_bits(data->regmap, DPS310_CFG_REG,
> -			       DPS310_TMP_SHIFT_EN, 0);
> +			       DPS310_PRS_SHIFT_EN | DPS310_TMP_SHIFT_EN, 0);
>  	if (rc < 0)
>  		return rc;
>  
> @@ -463,9 +774,9 @@ static int dps310_probe(struct i2c_client *client,
>  	if (rc < 0)
>  		return rc;
>  
> -	/* Turn on temperature measurement in the background */
> +	/* Turn on temperature and pressure measurement in the background */
>  	rc = regmap_write_bits(data->regmap, DPS310_MEAS_CFG,
> -			       DPS310_MEAS_CTRL_BITS,
> +			       DPS310_MEAS_CTRL_BITS, DPS310_PRS_EN |
>  			       DPS310_TEMP_EN | DPS310_BACKGROUND);
>  	if (rc < 0)
>  		return rc;
> @@ -479,7 +790,7 @@ static int dps310_probe(struct i2c_client *client,
>  	if (rc < 0)
>  		return rc;
>  
> -	rc = dps310_get_temp_coef(data);
> +	rc = dps310_get_coefs(data);
>  	if (rc < 0)
>  		return rc;
>  

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