Re: [PATCH v2] iio: ms5637: Add Measurement Specialties MS5637 support

[Jonathan Cameron <jic23@kernel.org>]

On 18/06/15 17:28, Ludovic wrote:
> This a patch re-submission taking into account feebdack from Peter and Tomasz.
> Thank you for your feedback
> 
> Ludovic
> 
> Signed-off-by: Ludovic <ludovic.tancerel@maplehightech.com>
Hi Ludovic,

Firstly would you mind signing off with your whole name prior to the email
address (convention in the kernel - if you have two or more names anyway ;)

Looking pretty good, just a few bits and bobs inline. Mostly along the
lines of ways of slightly cleaning up the code rather than anything
fundamental.

The one non trivial question is why the throttle on reading rate?

Jonathan
> ---
>  drivers/iio/pressure/Kconfig  |   9 +
>  drivers/iio/pressure/Makefile |   1 +
>  drivers/iio/pressure/ms5637.c | 457 ++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 467 insertions(+)
>  create mode 100644 drivers/iio/pressure/ms5637.c
> 
> diff --git a/drivers/iio/pressure/Kconfig b/drivers/iio/pressure/Kconfig
> index fa62950..69675ef2 100644
> --- a/drivers/iio/pressure/Kconfig
> +++ b/drivers/iio/pressure/Kconfig
> @@ -78,6 +78,15 @@ config MS5611_SPI
>  
>  	  To compile this driver as a module, choose M here: the module will
>  	  be called ms5611_spi.
> +config MS5637
> +        tristate "MS5637 pressure & temperature sensor"
> +        depends on I2C
> +        help
> +          If you say yes here you get support for the Measurement Specialties
> +          MS5637 pressure and temperature sensor.
> +
> +          This driver can also be built as a module. If so, the module will
> +          be called ms5637.
>  
>  config IIO_ST_PRESS
>  	tristate "STMicroelectronics pressure sensor Driver"
> diff --git a/drivers/iio/pressure/Makefile b/drivers/iio/pressure/Makefile
> index a4f98f8..46571c96 100644
> --- a/drivers/iio/pressure/Makefile
> +++ b/drivers/iio/pressure/Makefile
> @@ -10,6 +10,7 @@ obj-$(CONFIG_MPL3115) += mpl3115.o
>  obj-$(CONFIG_MS5611) += ms5611_core.o
>  obj-$(CONFIG_MS5611_I2C) += ms5611_i2c.o
>  obj-$(CONFIG_MS5611_SPI) += ms5611_spi.o
> +obj-$(CONFIG_MS5637) += ms5637.o
>  obj-$(CONFIG_IIO_ST_PRESS) += st_pressure.o
>  st_pressure-y := st_pressure_core.o
>  st_pressure-$(CONFIG_IIO_BUFFER) += st_pressure_buffer.o
> diff --git a/drivers/iio/pressure/ms5637.c b/drivers/iio/pressure/ms5637.c
> new file mode 100644
> index 0000000..bda7206
> --- /dev/null
> +++ b/drivers/iio/pressure/ms5637.c
> @@ -0,0 +1,457 @@
> +/*
> + * ms5637.c - Support for Measurement-Specialties ms5637
> + *            pressure & temperature sensor
> + *
> + * Copyright (c) 2014 Measurement-Specialties
> + *
> + * Licensed under the GPL-2.
> + *
> + * (7-bit I2C slave address 0x76)
> + *
> + */
> +#include <linux/init.h>
> +#include <linux/device.h>
> +#include <linux/kernel.h>
> +#include <linux/stat.h>
> +#include <linux/module.h>
> +#include <linux/i2c.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +#include <linux/jiffies.h>
> +#include <linux/delay.h>
> +#include <linux/mutex.h>
> +
> +/* MS5637 Commands */
> +#define MS5637_RESET				0x1E
> +#define MS5637_TEMPERATURE_CONVERSION_START	0x50
> +#define MS5637_PRESSURE_CONVERSION_START	0x40
> +#define MS5637_ADC_READ				0x00
> +#define MS5637_PROM_READ			0xA0
> +#define MS5637_PROM_ELEMENTS_NB                 7
> +
> +#define MS5637_CONVERSION_SLEEP(index)		\
> +		usleep_range(ms5637_conversion_time[index],\
> +		ms5637_conversion_time[index] + 3000)
I'd be tempted to make this one a function rather than a macro then
let the compiler inline it if it feels like it..
> +
> +static const u16 ms5637_conversion_time[6] = { 1000, 2000,
> +					       3000, 5000,
> +					       9000, 17000 };
> +
> +static const int ms5637_samp_freq[6][2]    = { {1800, 0}, {900, 0},
> +					       {450, 0}, {225, 0},
> +					       {112, 500000}, {56, 250000}
> +					     };
Although it is clearly duplicating data, I'd be tempted to have
the available list as a const char * here (where it can be easily checked).
Then you can drop a couple of functions and use the const attribute
defintion.

> +
> +struct ms5637_dev {
> +	struct i2c_client *client;
> +	struct mutex lock; /* Mutex protecting this data structure */
> +	/* Added element for CRC computation */
> +	u16 calibration_coeffs[MS5637_PROM_ELEMENTS_NB + 1];
> +	unsigned long last_update;
> +	int temperature;
> +	unsigned int pressure;
> +	u8 resolution_index;
> +};
> +
> +static int ms5637_get_calibration_coeffs(struct ms5637_dev *dev_data,
> +					 u8 index, u16 *word)
> +{
> +	int ret;
> +
> +	ret = i2c_smbus_read_word_swapped(dev_data->client,
> +					  MS5637_PROM_READ + (index << 1));
> +	if (ret < 0)
> +		return ret;
> +	*word = ret;
Blank line here.
> +	return 0;
> +}
> +
> +static bool ms5637_crc_check(u16 *n_prom, u8 crc)
> +{
> +	unsigned int cnt, n_bit;
> +	u16 n_rem, crc_read;
> +
> +	n_rem = 0x0000;
> +	crc_read = n_prom[0];
> +	n_prom[MS5637_PROM_ELEMENTS_NB] = 0;
> +	n_prom[0] &= 0x0FFF;      /* Clear the CRC computation part */
> +
> +	for (cnt = 0; cnt < (MS5637_PROM_ELEMENTS_NB + 1) * 2; cnt++) {
> +		if (cnt % 2 == 1)
> +			n_rem ^= n_prom[cnt >> 1] & 0x00FF;
> +		else
> +			n_rem ^= n_prom[cnt >> 1] >> 8;
> +
> +		for (n_bit = 8; n_bit > 0; n_bit--) {
> +			if (n_rem & 0x8000)
> +				n_rem = (n_rem << 1) ^ 0x3000;
> +			else
> +				n_rem <<= 1;
> +		}
> +	}
> +	n_rem >>= 12;
> +	n_prom[0] = crc_read;
blank line here.
> +	return n_rem == crc;
> +}
> +
> +static int ms5637_fill_calibration_coeffs(struct ms5637_dev *dev_data)
> +{
> +	int i, ret;
> +
> +	for (i = 0; i < MS5637_PROM_ELEMENTS_NB; i++) {
> +		ret = ms5637_get_calibration_coeffs(
> +					dev_data, i,
> +					&dev_data->calibration_coeffs[i]);
> +
> +		if (ret < 0) {
> +			dev_err(&dev_data->client->dev,
> +				"Unable to get calibration coefficients at address %d\n",
> +				i + 1);
> +			return ret;
> +		}
> +
> +		dev_dbg(&dev_data->client->dev, "Coeff %d : %d", i,
> +			dev_data->calibration_coeffs[i]);
> +	}
> +
> +	if ( ms5637_crc_check(
> +		dev_data->calibration_coeffs,
> +		(dev_data->calibration_coeffs[0] & 0xF000) >> 12) == false) {
> +		dev_err(&dev_data->client->dev,
> +			"Calibration coefficients crc check error\n");
> +		return -ENODEV;
> +	}
> +	return 0;
> +}
> +
> +static int ms5637_read_adc_value(struct ms5637_dev *dev_data, u32 *adc_value)
> +{
> +	int ret
This is a fairly standard beast.  I'd use a u32 and just set it to zero
before reading into the relevant address and using an endian conversion
to sort out the ordering if needed.  That way if no endian conversion
is needed it is all free ;)
> +	u8 buf[3];
> +
> +	ret =
> +	    i2c_smbus_read_i2c_block_data(dev_data->client, MS5637_ADC_READ, 3,
> +					  buf);
> +	if (ret < 0)
> +		return ret;
> +
> +	dev_dbg(&dev_data->client->dev, "ADC raw value : %x %x %x\n", buf[0],
> +		buf[1], buf[2]);
> +
> +	*adc_value = (buf[0] << 16) + (buf[1] << 8) + buf[2];
> +
> +	return 0;
> +}
> +
> +static int ms5637_conversion_and_read_adc(struct ms5637_dev *dev_data,
> +					  u32 *t_adc, u32 *p_adc)
> +{
> +	int ret;
> +
> +	/* Trigger Temperature conversion */
> +	ret = i2c_smbus_write_byte(dev_data->client,
> +				   MS5637_TEMPERATURE_CONVERSION_START
> +				   + dev_data->resolution_index * 2);
> +	if (ret < 0)
> +		return ret;
> +	MS5637_CONVERSION_SLEEP(dev_data->resolution_index);
> +
> +	/* Retrieve ADC value */
> +	ret = ms5637_read_adc_value(dev_data, t_adc);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* Trigger Pressure conversion */
> +	ret = i2c_smbus_write_byte(dev_data->client,
> +				   MS5637_PRESSURE_CONVERSION_START
> +				   + dev_data->resolution_index * 2);
> +	if (ret < 0)
> +		return ret;
> +	MS5637_CONVERSION_SLEEP(dev_data->resolution_index);
> +
> +	/* Retrieve ADC value */
> +	ret = ms5637_read_adc_value(dev_data, p_adc);
> +	if (ret < 0)
> +		return ret;
> +
> +	return 0;
> +}
> +
> +static int ms5637_read_temperature_and_pressure(struct ms5637_dev *dev_data)
> +{
> +	int ret = 0;
> +	u32 t_adc, p_adc;
> +	s32 dt, temp;
> +	s64 off, sens, t2, off2, sens2;
> +
> +	mutex_lock(&dev_data->lock);
> +
Why this throttle on frequency of reading?  If there is a reason
add a comment saying why.
> +	if (time_after(jiffies, dev_data->last_update + HZ / 2)) {
> +		ret = ms5637_conversion_and_read_adc(dev_data, &t_adc, &p_adc);
> +		if (ret < 0) {
> +			dev_err(&dev_data->client->dev,
> +				"Unable to make sensor adc conversion\n");
> +			goto out;
> +		}
> +
> +		dt = (s32)t_adc - (dev_data->calibration_coeffs[5] << 8);
> +
> +		/* Actual temperature = 2000 + dT * TEMPSENS */
> +		temp =
> +		    2000 + (((s64)dt * dev_data->calibration_coeffs[6]) >> 23);
> +
> +		/* Second order temperature compensation */
> +		if (temp < 2000) {
> +			s64 tmp = (s64)temp - 2000;
> +
> +			t2 = (3 * ((s64)dt * (s64)dt)) >> 33;
> +			off2 = (61 * tmp * tmp) >> 4;
> +			sens2 = (29 * tmp * tmp) >> 4;
> +
> +			if (temp < -1500) {
> +				s64 tmp = (s64)temp + 1500;
> +
> +				off2 += 17 * tmp * tmp;
> +				sens2 += 9 * tmp * tmp;
> +			}
> +		} else {
> +			t2 = (5 * ((s64)dt * (s64)dt)) >> 38;
> +			off2 = 0;
> +			sens2 = 0;
> +		}
> +
> +		/* OFF = OFF_T1 + TCO * dT */
> +		off = (((s64)dev_data->calibration_coeffs[2]) << 17) +
> +		    ((((s64)dev_data->calibration_coeffs[4]) * (s64)dt) >> 6);
> +		off -= off2;
> +
> +		/* Sensitivity at actual temperature = SENS_T1 + TCS * dT */
> +		sens = (((s64)dev_data->calibration_coeffs[1]) << 16)
> +		    + (((s64)dev_data->calibration_coeffs[3] * dt) >> 7);
> +		sens -= sens2;
> +
> +		/* Temperature compensated pressure = D1 * SENS - OFF */
> +		dev_data->temperature = (temp - t2) * 10;
> +		dev_data->pressure = (u32)(((((s64)p_adc * sens) >> 21)
> +					     - off) >> 15);
> +
> +		dev_data->last_update = jiffies;
> +	}
> + out:
> +	mutex_unlock(&dev_data->lock);
> +
> +	return ret >= 0 ? 0 : ret;
I'd just make sure that ret is firmly defined to only be an error if
negative then just return it directly.  (convention in the kernel is
for only negative errors).
> +}
> +
Again, this isn't complex enough or used enough to demand a utility function.

> +static int ms5637_get_int_plus_micros_index(const int (*vals)[2], int n,
> +					    int val, int val2)
> +{
> +	while (n-- > 0)
> +		if (val == vals[n][0] && val2 == vals[n][1])
> +			return n;
> +	return -EINVAL;
> +}
> +
Only used in one place. Roll this inline.  It's not complex enough
that this little utilty function is needed.
> +static int ms5637_get_samp_freq_index(struct ms5637_dev *dev_data,
> +				      int val, int val2)
> +{
> +	return ms5637_get_int_plus_micros_index(ms5637_samp_freq,
> +				ARRAY_SIZE(ms5637_samp_freq), val, val2);
> +}
> +
> +static ssize_t ms5637_show_int_plus_micros(char *buf,
> +					   const int (*vals)[2], int n)
> +{
> +	size_t len = 0;
> +
> +	while (n-- > 0)
> +		len += scnprintf(buf + len, PAGE_SIZE - len,
> +			"%d.%06d ", vals[n][0], vals[n][1]);
> +
> +	/* replace trailing space by newline */
> +	buf[len - 1] = '\n';
> +
> +	return len;
> +}
> +
> +static ssize_t ms5637_show_samp_freq_avail(struct device *dev,
> +					   struct device_attribute *attr,
> +					   char *buf)
> +{
> +	return ms5637_show_int_plus_micros(buf, ms5637_samp_freq,
> +					   ARRAY_SIZE(ms5637_samp_freq));
> +}
> +
> +static int ms5637_read_raw(struct iio_dev *indio_dev,
> +			   struct iio_chan_spec const *channel, int *val,
> +			   int *val2, long mask)
> +{
> +	int ret;
> +	struct ms5637_dev *dev_data = iio_priv(indio_dev);
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_PROCESSED:
> +		ret = ms5637_read_temperature_and_pressure(dev_data);
> +		if (ret)
> +			goto err;
> +		switch (channel->type) {
> +		case IIO_TEMP:	/* in °C */
> +			*val = dev_data->temperature / 1000;
> +			*val2 = (dev_data->temperature % 1000) * 1000;
> +			break;
> +		case IIO_PRESSURE:	/* in kPa */
> +			*val = dev_data->pressure / 1000;
> +			*val2 = (dev_data->pressure % 1000) * 1000;
> +			break;
> +		default:
> +			return -EINVAL;
> +		}
> +		break;
> +	case IIO_CHAN_INFO_SAMP_FREQ:
> +		*val = ms5637_samp_freq[dev_data->resolution_index][0];
> +		*val2 = ms5637_samp_freq[dev_data->resolution_index][1];
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	return IIO_VAL_INT_PLUS_MICRO;
I'd return directly from the various case statements.
> + err:
> +	dev_err(&indio_dev->dev, "Device read error\n");
You only get here from one place.  Do this inline.
> +	return ret;
> +}
> +
> +static int ms5637_write_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int val, int val2, long mask)
> +{
> +	struct ms5637_dev *dev_data = iio_priv(indio_dev);
> +	int i;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_SAMP_FREQ:
> +		i = ms5637_get_samp_freq_index(dev_data, val, val2);
> +		if (i < 0)
> +			return -EINVAL;
> +
> +		dev_data->resolution_index = i;
Nitpick of the day.  A blank line here would be perfect ;)
> +		return 0;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static const struct iio_chan_spec ms5637_channels[] = {
> +	{
The indenting you are using here is somewhat unusual.  Give the
entries another tab.
> +	 .type = IIO_TEMP,
> +	 .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
> +	 .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SAMP_FREQ),
> +	 },
> +	{
> +	 .type = IIO_PRESSURE,
> +	 .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
> +	 .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SAMP_FREQ),
> +	 }
> +};
> +
> +static IIO_DEV_ATTR_SAMP_FREQ_AVAIL(ms5637_show_samp_freq_avail);
> +
> +static struct attribute *ms5637_attributes[] = {
> +	&iio_dev_attr_sampling_frequency_available.dev_attr.attr,
> +	NULL,
> +};
> +
> +static const struct attribute_group ms5637_attribute_group = {
> +	.attrs = ms5637_attributes,
> +};
> +
> +static const struct iio_info ms5637_info = {
> +	.read_raw = ms5637_read_raw,
> +	.write_raw = ms5637_write_raw,
> +	.attrs = &ms5637_attribute_group,
> +	.driver_module = THIS_MODULE,
> +};
> +
> +static int ms5637_probe(struct i2c_client *client,
> +			const struct i2c_device_id *id)
> +{
> +	struct ms5637_dev *dev_data;
> +	struct iio_dev *indio_dev;
> +	int ret;
> +
The func parameter passed into i2c_check_functionality is a bitmap so
do all these in one call.
if (!i2c_check_functionality(client->adapter,
                             I2C_FUNC_SMBUS_READ_WORD_DATA |
			     I2C_FUNC_SMBUS_WRITE_BYTE |
			     I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
etc.

> +	if (!i2c_check_functionality(client->adapter,
> +				     I2C_FUNC_SMBUS_READ_WORD_DATA)) {
> +		dev_err(&client->dev,
> +			"Adapter does not support SMBus read word transactions\n");
> +		return -ENODEV;
> +	}
> +
> +	if (!i2c_check_functionality(client->adapter,
> +				     I2C_FUNC_SMBUS_WRITE_BYTE)) {
> +		dev_err(&client->dev,
> +			"Adapter does not support SMBus write byte transactions\n");
> +		return -ENODEV;
> +	}
> +
> +	if (!i2c_check_functionality(client->adapter,
> +				     I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
> +		dev_err(&client->dev,
> +			"Adapter does not support SMBus read block transactions\n");
> +		return -ENODEV;
> +	}
> +
> +	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*dev_data));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	dev_data = iio_priv(indio_dev);
> +	dev_data->client = client;
> +	dev_data->resolution_index = 5;
> +	dev_data->last_update = jiffies - HZ / 2;
> +	mutex_init(&dev_data->lock);
> +
> +	indio_dev->info = &ms5637_info;
> +	indio_dev->name = id->name;
> +	indio_dev->dev.parent = &client->dev;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = ms5637_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(ms5637_channels);
> +
> +	i2c_set_clientdata(client, indio_dev);
> +	ret = i2c_smbus_write_byte(client, MS5637_RESET);
> +	if (ret < 0)
> +		return ret;
> +	usleep_range(3000, 6000);
> +
> +	ret = ms5637_fill_calibration_coeffs(dev_data);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = devm_iio_device_register(&client->dev, indio_dev);
> +	if (ret < 0)
> +		return ret;
> +
> +	dev_dbg(&client->dev, "Driver initialization done");
There are a lot of ways fo telling it is finsihed ;)  I'd drop this
particular debug output from a driver just before submitting it.

> +	return 0;
> +}
> +
> +static const struct i2c_device_id ms5637_id[] = {
> +	{"ms5637", 0},
> +	{}
> +};
> +
> +static struct i2c_driver ms5637_driver = {
> +	.probe = ms5637_probe,
> +	.id_table = ms5637_id,
> +	.driver = {
> +		   .name = "ms5637",
> +		   .owner = THIS_MODULE,
> +		   },
> +};
> +
> +module_i2c_driver(ms5637_driver);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("Measurement-Specialties ms5637 temperature & pressure driver");
> +MODULE_AUTHOR("William Markezana <william.markezana@meas-spec.com>");
> +MODULE_AUTHOR("Ludovic Tancerel <ludovic.tancerel@maplehightech.com>");
> 

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