Re: [PATCH v2 1/3] iio: magnetometer: Add support for MEMSIC MMC35240 sensor

[Hartmut Knaack]

Daniel Baluta schrieb am 24.04.2015 um 17:58:
> Minimal implementation for MMC35240 3-axis magnetometer
> sensor. It provides processed readings and possiblity to change
> the sampling frequency.
> 

Hi Daniel,
please find a few issues inline, which you could address in a next
rework patch set. I would have sent a patch for the critical stuff,
but was obviously too stupid to find a data sheet :-(

> Signed-off-by: Daniel Baluta <daniel.baluta@xxxxxxxxx>
> ---
>  drivers/iio/magnetometer/Kconfig    |  11 +
>  drivers/iio/magnetometer/Makefile   |   1 +
>  drivers/iio/magnetometer/mmc35240.c | 468 ++++++++++++++++++++++++++++++++++++
>  3 files changed, 480 insertions(+)
>  create mode 100644 drivers/iio/magnetometer/mmc35240.c
> 
> diff --git a/drivers/iio/magnetometer/Kconfig b/drivers/iio/magnetometer/Kconfig
> index a5d6de7..7aba685 100644
> --- a/drivers/iio/magnetometer/Kconfig
> +++ b/drivers/iio/magnetometer/Kconfig
> @@ -47,6 +47,17 @@ config HID_SENSOR_MAGNETOMETER_3D
>  	  Say yes here to build support for the HID SENSOR
>  	  Magnetometer 3D.
>  
> +config MMC35240
> +	tristate "MEMSIC MMC35240 3-axis magnetic sensor"
> +	select REGMAP_I2C
> +	depends on I2C
> +	help
> +	  Say yes here to build support for the MEMSIC MMC35240 3-axis
> +	  magnetic sensor.
> +
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called mmc35240.
> +
>  config IIO_ST_MAGN_3AXIS
>  	tristate "STMicroelectronics magnetometers 3-Axis Driver"
>  	depends on (I2C || SPI_MASTER) && SYSFS
> diff --git a/drivers/iio/magnetometer/Makefile b/drivers/iio/magnetometer/Makefile
> index 0f5d3c9..696a429 100644
> --- a/drivers/iio/magnetometer/Makefile
> +++ b/drivers/iio/magnetometer/Makefile
> @@ -6,6 +6,7 @@
>  obj-$(CONFIG_AK8975)	+= ak8975.o
>  obj-$(CONFIG_MAG3110)	+= mag3110.o
>  obj-$(CONFIG_HID_SENSOR_MAGNETOMETER_3D) += hid-sensor-magn-3d.o
> +obj-$(CONFIG_MMC35240)	+= mmc35240.o
>  
>  obj-$(CONFIG_IIO_ST_MAGN_3AXIS) += st_magn.o
>  st_magn-y := st_magn_core.o
> diff --git a/drivers/iio/magnetometer/mmc35240.c b/drivers/iio/magnetometer/mmc35240.c
> new file mode 100644
> index 0000000..beefebc
> --- /dev/null
> +++ b/drivers/iio/magnetometer/mmc35240.c
> @@ -0,0 +1,468 @@
> +/*
> + * MMC35240 - MEMSIC 3-axis Magnetic Sensor
> + *
> + * Copyright (c) 2015, Intel Corporation.
> + *
> + * This file is subject to the terms and conditions of version 2 of
> + * the GNU General Public License.  See the file COPYING in the main
> + * directory of this archive for more details.
> + *
> + * IIO driver for MMC35240 (7-bit I2C slave address 0x30).
> + *
> + * TODO: offset, ACPI, continuous measurement mode, PM
> + */
> +
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/i2c.h>
> +#include <linux/delay.h>
> +#include <linux/regmap.h>
> +
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +
> +#define MMC35240_DRV_NAME "mmc35240"
> +#define MMC35240_REGMAP_NAME "mmc35240_regmap"
> +
> +#define MMC35240_REG_XOUT_L	0x00
> +#define MMC35240_REG_XOUT_H	0x01
> +#define MMC35240_REG_YOUT_L	0x02
> +#define MMC35240_REG_YOUT_H	0x03
> +#define MMC35240_REG_ZOUT_L	0x04
> +#define MMC35240_REG_ZOUT_H	0x05
> +
> +#define MMC35240_REG_STATUS	0x06
> +#define MMC35240_REG_CTRL0	0x07
> +#define MMC35240_REG_CTRL1	0x08
> +
> +#define MMC35240_REG_ID		0x20
> +
> +#define MMC35240_STATUS_MEAS_DONE_BIT	BIT(0)
> +
> +#define MMC35240_CTRL0_REFILL_BIT	BIT(7)
> +#define MMC35240_CTRL0_RESET_BIT	BIT(6)
> +#define MMC35240_CTRL0_SET_BIT		BIT(5)
> +#define MMC35240_CTRL0_CMM_BIT		BIT(1)
> +#define MMC35240_CTRL0_TM_BIT		BIT(0)

It took me quite some time to figure out TM would stand for take measurement.
Still no clue about CMM (it's still not used from what I could see). Would be
great if you could comment them.

> +
> +/* output resolution bits */
> +#define MMC35240_CTRL1_BW0_BIT		BIT(0)
> +#define MMC35240_CTRL1_BW1_BIT		BIT(1)
> +
> +#define MMC35240_CTRL1_BW_MASK	 (MMC35240_CTRL1_BW0_BIT | \
> +		 MMC35240_CTRL1_BW1_BIT)
> +#define MMC35240_CTRL1_BW_SHIFT		0
> +
> +#define MMC35240_WAIT_CHARGE_PUMP	50000	/* us */
> +#define MMC53240_WAIT_SET_RESET		1000	/* us */
> +
> +enum mmc35240_resolution {
> +	MMC35240_16_BITS_SLOW = 0, /* 100 Hz */
> +	MMC35240_16_BITS_FAST,     /* 200 Hz */
> +	MMC35240_14_BITS,          /* 333 Hz */
> +	MMC35240_12_BITS,          /* 666 Hz */
> +};
> +
> +enum mmc35240_axis {
> +	AXIS_X = 0,
> +	AXIS_Y,
> +	AXIS_Z,
> +};
> +
> +static const struct {
> +	int sens[3]; /* sensitivity per X, Y, Z axis */
> +	int nfo; /* null field output */
> +} mmc35240_props_table[] = {
> +	/* 16 bits, 100Hz ODR */
> +	{
> +		{1024, 1024, 770},
> +		32768,
> +	},
> +	/* 16 bits, 200Hz ODR */
> +	{
> +		{1024, 1024, 770},
> +		32768,
> +	},
> +	/* 14 bits, 333Hz ODR */
> +	{
> +		{256, 256, 193},
> +		8192,
> +	},
> +	/* 12 bits, 666Hz ODR */
> +	{
> +		{64, 64, 48},
> +		2048,
> +	},
> +};
> +
> +struct mmc35240_data {
> +	struct i2c_client *client;
> +	struct mutex mutex;
> +	struct regmap *regmap;
> +	enum mmc35240_resolution res;
> +};
> +
> +int mmc35240_samp_freq[] = {100, 200, 333, 666};
> +
> +static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("100 200 333 666");
> +
> +#define MMC35240_CHANNEL(_axis) { \
> +	.type = IIO_MAGN, \
> +	.modified = 1, \
> +	.channel2 = IIO_MOD_ ## _axis, \
> +	.address = AXIS_ ## _axis, \
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), \
> +	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SAMP_FREQ), \
> +}
> +
> +static const struct iio_chan_spec mmc35240_channels[] = {
> +	MMC35240_CHANNEL(X),
> +	MMC35240_CHANNEL(Y),
> +	MMC35240_CHANNEL(Z),
> +};
> +
> +static struct attribute *mmc35240_attributes[] = {
> +	&iio_const_attr_sampling_frequency_available.dev_attr.attr,
> +};
> +
> +static const struct attribute_group mmc35240_attribute_group = {
> +	.attrs = mmc35240_attributes,
> +};
> +
> +static int mmc35240_get_samp_freq_index(struct mmc35240_data *data,
> +					int val, int val2)
> +{
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(mmc35240_samp_freq); i++)
> +		if (mmc35240_samp_freq[i] == val)
> +			return i;
> +	return -EINVAL;
> +}
> +
> +static int mmc35240_hw_set(struct mmc35240_data *data, bool set)
> +{
> +	int ret;
> +	u8 coil_bit;
> +
> +	/*
> +	 * Recharge the capacitor at VCAP pin, requested to be issued
> +	 * before a SET/RESET command.
> +	 */
> +	ret = regmap_update_bits(data->regmap, MMC35240_REG_CTRL0,
> +				 MMC35240_CTRL0_REFILL_BIT,
> +				 MMC35240_CTRL0_REFILL_BIT);
> +	if (ret < 0)
> +		return ret;
> +	usleep_range(MMC35240_WAIT_CHARGE_PUMP, MMC35240_WAIT_CHARGE_PUMP + 1);
> +
> +	if (set)
> +		coil_bit = MMC35240_CTRL0_SET_BIT;
> +	else
> +		coil_bit = MMC35240_CTRL0_RESET_BIT;
> +
> +	return regmap_update_bits(data->regmap, MMC35240_REG_CTRL0,
> +				  MMC35240_CTRL0_REFILL_BIT,
> +				  coil_bit);

coil_bit is in any case outside the mask of MMC35240_CTRL0_REFILL_BIT.
Not sure about the whole intention, meaning in which state 
MMC35240_CTRL0_REFILL_BIT is supposed to be (set) when either
MMC35240_CTRL0_SET_BIT or MMC35240_CTRL0_RESET_BIT is written.

> +}
> +
> +static int mmc35240_init(struct mmc35240_data *data)
> +{
> +	int ret;
> +	unsigned int reg_id;
> +
> +	ret = regmap_read(data->regmap, MMC35240_REG_ID, &reg_id);
> +	if (ret < 0) {
> +		dev_err(&data->client->dev, "Error reading product id\n");
> +		return ret;
> +	}
> +
> +	dev_dbg(&data->client->dev, "MMC35240 chip id %x\n", reg_id);
> +
> +	/*
> +	 * make sure we restore sensor characteristics, by doing
> +	 * a RESET/SET sequence
> +	 */
> +	ret = mmc35240_hw_set(data, false);
> +	if (ret < 0)
> +		return ret;
> +	usleep_range(MMC53240_WAIT_SET_RESET, MMC53240_WAIT_SET_RESET + 1);
> +
> +	ret = mmc35240_hw_set(data, true);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* set default sampling frequency */
> +	return regmap_update_bits(data->regmap, MMC35240_REG_CTRL1,
> +				  MMC35240_CTRL1_BW_MASK,
> +				  data->res << MMC35240_CTRL1_BW_SHIFT);
> +}
> +
> +static int mmc35240_take_measurement(struct mmc35240_data *data)
> +{
> +	int ret, tries = 100;
> +	unsigned int reg_status;
> +
> +	ret = regmap_write(data->regmap, MMC35240_REG_CTRL0,
> +			   MMC35240_CTRL0_TM_BIT);
> +	if (ret < 0)
> +		return ret;
> +
> +	while (tries-- > 0) {
> +		ret = regmap_read(data->regmap, MMC35240_REG_STATUS,
> +				  &reg_status);
> +		if (ret < 0)
> +			return ret;
> +		if (reg_status & MMC35240_STATUS_MEAS_DONE_BIT)
> +			break;

I would actually return 0 here, as measurement was successful. That
would mean that getting outside the loop is the error case and would
make the check obsolete.

> +		msleep(20);
> +	}
> +
> +	if (tries < 0) {
> +		dev_err(&data->client->dev, "data not ready\n");
> +		return -EIO;

Doesn't this qualify more for a timeout error, rather than I/O?

> +	}
> +
> +	return 0;
> +}
> +
> +static int mmc35240_read_measurement(struct mmc35240_data *data, __le16 buf[3])
> +{
> +	int ret;
> +
> +	ret = mmc35240_take_measurement(data);
> +	if (ret < 0)
> +		return ret;
> +
> +	return regmap_bulk_read(data->regmap, MMC35240_REG_XOUT_L, (u8 *)buf,
> +				3 * sizeof(__le16));
> +}
> +
> +int mmc35240_raw_to_gauss(struct mmc35240_data *data, int index, __le16 buf[],
> +			  int *val, int *val2)
> +{
> +	int raw_x, raw_y, raw_z;
> +	int sens_x, sens_y, sens_z;
> +	int nfo;
> +
> +	raw_x = le16_to_cpu(buf[AXIS_X]);
> +	raw_y = le16_to_cpu(buf[AXIS_Y]);
> +	raw_z = le16_to_cpu(buf[AXIS_Z]);
> +
> +	sens_x = mmc35240_props_table[data->res].sens[AXIS_X];
> +	sens_y = mmc35240_props_table[data->res].sens[AXIS_Y];
> +	sens_z = mmc35240_props_table[data->res].sens[AXIS_Z];
> +
> +	nfo = mmc35240_props_table[data->res].nfo;
> +
> +	switch (index) {
> +	case AXIS_X:
> +		*val = (raw_x - nfo) / sens_x;
> +		*val2 = ((raw_x - nfo) % sens_x) * 1000000;
> +		break;
> +	case AXIS_Y:
> +		*val = (raw_y - nfo) / sens_y - (raw_z - nfo) / sens_z;
> +		*val2 = (((raw_y - nfo) % sens_y - (raw_z - nfo) % sens_z))
> +			* 1000000;
> +		break;
> +	case AXIS_Z:
> +		*val = (raw_y - nfo) / sens_y + (raw_z - nfo) / sens_z;
> +		*val2 = (((raw_y - nfo) % sens_y + (raw_z - nfo) % sens_z))
> +			* 1000000;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +	return 0;
> +}
> +
> +static int mmc35240_read_raw(struct iio_dev *indio_dev,
> +			     struct iio_chan_spec const *chan, int *val,
> +			     int *val2, long mask)
> +{
> +	struct mmc35240_data *data = iio_priv(indio_dev);
> +	int ret, i;
> +	unsigned int reg;
> +	__le16 buf[3];
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_PROCESSED:
> +		mutex_lock(&data->mutex);
> +		ret = mmc35240_read_measurement(data, buf);
> +		mutex_unlock(&data->mutex);
> +		if (ret < 0)
> +			return ret;
> +		ret = mmc35240_raw_to_gauss(data, chan->address,
> +					    buf, val, val2);
> +		if (ret < 0)
> +			return ret;
> +		return IIO_VAL_INT_PLUS_MICRO;
> +	case IIO_CHAN_INFO_SAMP_FREQ:
> +		mutex_lock(&data->mutex);
> +		ret = regmap_read(data->regmap, MMC35240_REG_CTRL1, &reg);
> +		mutex_unlock(&data->mutex);
> +		if (ret < 0)
> +			return ret;
> +
> +		i = (reg & MMC35240_CTRL1_BW_MASK) >> MMC35240_CTRL1_BW_SHIFT;
> +		if (i < 0 || i > ARRAY_SIZE(mmc35240_samp_freq))

I would drop i and keep using reg. Has the nice side effect that you don't
need to check for negative values.

> +			return -EINVAL;
> +
> +		*val = mmc35240_samp_freq[i];
> +		*val2 = 0;
> +		return IIO_VAL_INT;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int mmc35240_write_raw(struct iio_dev *indio_dev,
> +			      struct iio_chan_spec const *chan, int val,
> +			      int val2, long mask)
> +{
> +	struct mmc35240_data *data = iio_priv(indio_dev);
> +	int i, ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_SAMP_FREQ:
> +		i = mmc35240_get_samp_freq_index(data, val, val2);
> +		if (i < 0)
> +			return -EINVAL;
> +		mutex_lock(&data->mutex);
> +		ret = regmap_update_bits(data->regmap, MMC35240_REG_CTRL1,
> +					 MMC35240_CTRL1_BW_MASK,
> +					 i << MMC35240_CTRL1_BW_SHIFT);
> +		mutex_unlock(&data->mutex);
> +		return ret;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static const struct iio_info mmc35240_info = {
> +	.driver_module	= THIS_MODULE,
> +	.read_raw	= mmc35240_read_raw,
> +	.write_raw	= mmc35240_write_raw,
> +	.attrs		= &mmc35240_attribute_group,
> +};
> +
> +static bool mmc35240_is_writeable_reg(struct device *dev, unsigned int reg)
> +{
> +	switch (reg) {
> +	case MMC35240_REG_CTRL0:
> +	case MMC35240_REG_CTRL1:
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> +
> +static bool mmc35240_is_readable_reg(struct device *dev, unsigned int reg)
> +{
> +	switch (reg) {
> +	case MMC35240_REG_XOUT_L:
> +	case MMC35240_REG_XOUT_H:
> +	case MMC35240_REG_YOUT_L:
> +	case MMC35240_REG_YOUT_H:
> +	case MMC35240_REG_ZOUT_L:
> +	case MMC35240_REG_ZOUT_H:
> +	case MMC35240_REG_STATUS:
> +	case MMC35240_REG_ID:
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> +
> +static bool mmc35240_is_volatile_reg(struct device *dev, unsigned int reg)
> +{
> +	switch (reg) {
> +	case MMC35240_REG_CTRL0:
> +	case MMC35240_REG_CTRL1:

I would regard MMC35240_REG_ID as non-volatile, as well. Or is it because it
is just accessed once?

Thanks,
Hartmut

> +		return false;
> +	default:
> +		return true;
> +	}
> +}
> +
> +static struct reg_default mmc35240_reg_defaults[] = {
> +	{ MMC35240_REG_CTRL0,  0x00 },
> +	{ MMC35240_REG_CTRL1,  0x00 },
> +};
> +
> +static const struct regmap_config mmc35240_regmap_config = {
> +	.name = MMC35240_REGMAP_NAME,
> +
> +	.reg_bits = 8,
> +	.val_bits = 8,
> +
> +	.max_register = MMC35240_REG_ID,
> +	.cache_type = REGCACHE_FLAT,
> +
> +	.writeable_reg = mmc35240_is_writeable_reg,
> +	.readable_reg = mmc35240_is_readable_reg,
> +	.volatile_reg = mmc35240_is_volatile_reg,
> +
> +	.reg_defaults = mmc35240_reg_defaults,
> +	.num_reg_defaults = ARRAY_SIZE(mmc35240_reg_defaults),
> +};
> +
> +static int mmc35240_probe(struct i2c_client *client,
> +			  const struct i2c_device_id *id)
> +{
> +	struct mmc35240_data *data;
> +	struct iio_dev *indio_dev;
> +	struct regmap *regmap;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	regmap = devm_regmap_init_i2c(client, &mmc35240_regmap_config);
> +	if (IS_ERR(regmap)) {
> +		dev_err(&client->dev, "regmap initialization failed\n");
> +		return PTR_ERR(regmap);
> +	}
> +
> +	data = iio_priv(indio_dev);
> +	data->client = client;
> +	data->regmap = regmap;
> +	data->res = MMC35240_16_BITS_SLOW;
> +
> +	mutex_init(&data->mutex);
> +
> +	indio_dev->dev.parent = &client->dev;
> +	indio_dev->info = &mmc35240_info;
> +	indio_dev->name = MMC35240_DRV_NAME;
> +	indio_dev->channels = mmc35240_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(mmc35240_channels);
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +
> +	ret = mmc35240_init(data);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "mmc35240 chip init failed\n");
> +		return ret;
> +	}
> +	return devm_iio_device_register(&client->dev, indio_dev);
> +}
> +
> +static const struct i2c_device_id mmc35240_id[] = {
> +	{"MMC35240", 0},
> +	{}
> +};
> +MODULE_DEVICE_TABLE(i2c, mmc35240_id);
> +
> +static struct i2c_driver mmc35240_driver = {
> +	.driver = {
> +		.name = MMC35240_DRV_NAME,
> +	},
> +	.probe		= mmc35240_probe,
> +	.id_table	= mmc35240_id,
> +};
> +
> +module_i2c_driver(mmc35240_driver);
> +
> +MODULE_AUTHOR("Daniel Baluta <daniel.baluta@xxxxxxxxx>");
> +MODULE_DESCRIPTION("MEMSIC MMC35240 magnetic sensor driver");
> +MODULE_LICENSE("GPL v2");
> 

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