Re: [PATCH v4] iio: magnetometer: add mmc34160 magnetometer driver

[Teodora Baluta]

On Mon, Aug 17, 2015 at 09:28:41PM +0200, Peter Meerwald wrote:
> On Mon, 17 Aug 2015, Teodora Baluta wrote:
> 
> > This patch adds support for the MMC34160 3-axis magnetometer driver. The
> > MMC31460 magnetometer driver uses the same register map as MMC35240 with
> > different specifications for sensitivity.
> > 
> > According to Memsic specification, for the MMC31460 sensor, there is no
> > need to apply compensation to the read values. Also, the MMC34160 sensor
> > does not use the same formula as MMC35240 for transforming raw data into
> > mgauss, and the current formula is based on the input driver (mmc3416x)
> > provided by Memsic.
> 
> comments below

Hi Peter,

Thanks for the review! I'll address the comments in a v5 patch. Some
answers below.

>  
> > Signed-off-by: Teodora Baluta <teodora.baluta@xxxxxxxxx>
> > ---
> > Changes since v3:
> > - rebased to apply correctly
> > - include bits that went missing from v2 to v3
> > - remove return variable from mmc34160_raw_to_mgauss function
> > 
> >  drivers/iio/magnetometer/Kconfig    |   4 +-
> >  drivers/iio/magnetometer/mmc35240.c | 205 ++++++++++++++++++++++++++++--------
> >  2 files changed, 162 insertions(+), 47 deletions(-)
> > 
> > diff --git a/drivers/iio/magnetometer/Kconfig b/drivers/iio/magnetometer/Kconfig
> > index 868abad..df3f4cc 100644
> > --- a/drivers/iio/magnetometer/Kconfig
> > +++ b/drivers/iio/magnetometer/Kconfig
> > @@ -70,8 +70,8 @@ config MMC35240
> >  	select REGMAP_I2C
> >  	depends on I2C
> >  	help
> > -	  Say yes here to build support for the MEMSIC MMC35240 3-axis
> > -	  magnetic sensor.
> > +	  Say yes here to build support for the MEMSIC MMC35240 and MMC34160
> > +	  3-axis magnetic sensors.
> >  
> >  	  To compile this driver as a module, choose M here: the module
> >  	  will be called mmc35240.
> > diff --git a/drivers/iio/magnetometer/mmc35240.c b/drivers/iio/magnetometer/mmc35240.c
> > index 176e14a..e4fc5e4 100644
> > --- a/drivers/iio/magnetometer/mmc35240.c
> > +++ b/drivers/iio/magnetometer/mmc35240.c
> > @@ -83,6 +83,20 @@
> >  
> >  #define MMC35240_OTP_START_ADDR		0x1B
> >  
> > +#define MMC35240_CHIP_ID	0x08
> > +#define MMC34160_CHIP_ID	0x06
> > +
> > +enum mmc35240_chipset {
> > +	MMC35240,
> > +	MMC34160,
> > +	MMC_MAX_CHIPS
> > +};
> > +
> > +static u8 chip_ids[MMC_MAX_CHIPS] = {
> 
> mmc35240_ prefix missing
> 
> > +	MMC35240_CHIP_ID,
> > +	MMC34160_CHIP_ID,
> > +};
> > +
> >  enum mmc35240_resolution {
> >  	MMC35240_16_BITS_SLOW = 0, /* 7.92 ms */
> >  	MMC35240_16_BITS_FAST,     /* 4.08 ms */
> > @@ -99,27 +113,53 @@ enum mmc35240_axis {
> >  static const struct {
> >  	int sens[3]; /* sensitivity per X, Y, Z axis */
> >  	int nfo; /* null field output */
> > -} mmc35240_props_table[] = {
> > -	/* 16 bits, 125Hz ODR */
> > -	{
> > -		{1024, 1024, 1024},
> > -		32768,
> > -	},
> > -	/* 16 bits, 250Hz ODR */
> > -	{
> > -		{1024, 1024, 770},
> > -		32768,
> > -	},
> > -	/* 14 bits, 450Hz ODR */
> > +} mmc35240_props_table[MMC_MAX_CHIPS][4] = {
> > +	/* MMC35240 */
> >  	{
> > -		{256, 256, 193},
> > -		8192,
> > +		/* 16 bits, 125Hz ODR */
> > +		{
> > +			{1024, 1024, 1024},
> > +			32768,
> > +		},
> > +		/* 16 bits, 250Hz ODR */
> > +		{
> > +			{1024, 1024, 770},
> > +			32768,
> > +		},
> > +		/* 14 bits, 450Hz ODR */
> > +		{
> > +			{256, 256, 193},
> > +			8192,
> > +		},
> > +		/* 12 bits, 800Hz ODR */
> > +		{
> > +			{64, 64, 48},
> > +			2048,
> > +		},
> >  	},
> > -	/* 12 bits, 800Hz ODR */
> > +	/* MMC34160 */
> >  	{
> > -		{64, 64, 48},
> > -		2048,
> > -	},
> > +		/* 16 bits, 125Hz ODR */
> > +		{
> > +			{2048, 2048, 2048},
> > +			32768,
> > +		},
> > +		/* 16 bits, 250Hz ODR */
> > +		{
> > +			{2048, 2048, 2048},
> > +			32768,
> > +		},
> > +		/* 14 bits, 450Hz ODR */
> > +		{
> > +			{512, 512, 512},
> > +			8192,
> > +		},
> > +		/* 12 bits, 800Hz ODR */
> > +		{
> > +			{128, 128, 128},
> > +			2048,
> > +		},
> > +	}
> >  };
> >  
> >  struct mmc35240_data {
> > @@ -131,6 +171,7 @@ struct mmc35240_data {
> >  	/* OTP compensation */
> >  	int axis_coef[3];
> >  	int axis_scale[3];
> > +	enum mmc35240_chipset chipset;
> >  };
> >  
> >  static const struct {
> > @@ -206,6 +247,16 @@ static int mmc35240_hw_set(struct mmc35240_data *data, bool set)
> >  
> >  }
> >  
> > +static inline bool mmc35240_needs_compensation(enum mmc35240_chipset chipset)
> 
> maybe drop inline and let the compiler figure out

Did not take into account that the compiler can decide this for us,
though it seems pretty straight-forward it will inline it. I'll drop the
inline then.

> 
> > +{
> > +	switch (chipset) {
> > +	case MMC35240:
> > +		return true;
> > +	default:
> > +		return false;
> > +	}
> > +}
> > +
> >  static int mmc35240_init(struct mmc35240_data *data)
> >  {
> >  	int ret, y_convert, z_convert;
> > @@ -220,6 +271,11 @@ static int mmc35240_init(struct mmc35240_data *data)
> >  
> >  	dev_dbg(&data->client->dev, "MMC35240 chip id %x\n", reg_id);
> >  
> > +	if (reg_id != chip_ids[data->chipset]) {
> > +		dev_err(&data->client->dev, "Invalid chip %x\n", ret);
> > +		return -ENODEV;
> > +	}
> > +
> >  	/*
> >  	 * make sure we restore sensor characteristics, by doing
> >  	 * a SET/RESET sequence, the axis polarity being naturally
> > @@ -241,6 +297,9 @@ static int mmc35240_init(struct mmc35240_data *data)
> >  	if (ret < 0)
> >  		return ret;
> >  
> > +	if (!mmc35240_needs_compensation(data->chipset))
> > +		return 0;
> > +
> >  	ret = regmap_bulk_read(data->regmap, MMC35240_OTP_START_ADDR,
> >  			       (u8 *)otp_data, sizeof(otp_data));
> >  	if (ret < 0)
> > @@ -302,9 +361,37 @@ static int mmc35240_read_measurement(struct mmc35240_data *data, __le16 buf[3])
> >  				3 * sizeof(__le16));
> >  }
> >  
> > +static int mmc34160_raw_to_mgauss(int raw[3], int sens[3], int nfo,
> > +				  int index, int *val)
> > +{
> > +	return (raw[index] - nfo) * 1000 / sens[index];
> > +}
> > +
> > +static int mmc35240_raw_to_mgauss(int raw[3], int sens[3], int nfo,
> > +				  int index, int *val)
> > +{
> > +	switch (index) {
> > +	case AXIS_X:
> > +		*val = (raw[AXIS_X] - nfo) * 1000 / sens[AXIS_X];
> > +		break;
> > +	case AXIS_Y:
> > +		*val = (raw[AXIS_Y] - nfo) * 1000 / sens[AXIS_Y] -
> > +			(raw[AXIS_Z] - nfo)  * 1000 / sens[AXIS_Z];
> > +		break;
> > +	case AXIS_Z:
> > +		*val = (raw[AXIS_Y] - nfo) * 1000 / sens[AXIS_Y] +
> > +			(raw[AXIS_Z] - nfo) * 1000 / sens[AXIS_Z];
> > +		break;
> > +	default:
> > +		return -EINVAL;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> >  /**
> > - * mmc35240_raw_to_mgauss - convert raw readings to milli gauss. Also apply
> > -			    compensation for output value.
> > + * memsic_raw_to_mgauss - convert raw readings to milli gauss. Also apply
> > +			  compensation for output value.
> 
> why the name change?

Used the prefix for chip specific conversion - see
mmc35240_raw_to_mgauss and mmc34160_raw_to_mgauss.

I could keep the prefix for this one function and rename it to
mmc35240_raw_to_mgauss_comp (since it applies compensation as well),
remove the mmc34160_raw_to_mgauss function and put the formula directly
and keep the mmc35240_raw_to_mgauss as it is. Would that be better?

> 
> >   *
> >   * @data: device private data
> >   * @index: axis index for which we want the conversion
> > @@ -313,40 +400,42 @@ static int mmc35240_read_measurement(struct mmc35240_data *data, __le16 buf[3])
> >   *
> >   * Returns: 0 in case of success, -EINVAL when @index is not valid
> >   */
> > -static int mmc35240_raw_to_mgauss(struct mmc35240_data *data, int index,
> > -				  __le16 buf[], int *val)
> > +static int memsic_raw_to_mgauss(struct mmc35240_data *data, int index,
> > +				__le16 buf[], int *val)
> >  {
> >  	int raw[3];
> >  	int sens[3];
> >  	int nfo;
> > +	int ret;
> > +	int id = data->chipset;
> >  
> >  	raw[AXIS_X] = le16_to_cpu(buf[AXIS_X]);
> >  	raw[AXIS_Y] = le16_to_cpu(buf[AXIS_Y]);
> >  	raw[AXIS_Z] = le16_to_cpu(buf[AXIS_Z]);
> >  
> > -	sens[AXIS_X] = mmc35240_props_table[data->res].sens[AXIS_X];
> > -	sens[AXIS_Y] = mmc35240_props_table[data->res].sens[AXIS_Y];
> > -	sens[AXIS_Z] = mmc35240_props_table[data->res].sens[AXIS_Z];
> > +	sens[AXIS_X] = mmc35240_props_table[id][data->res].sens[AXIS_X];
> > +	sens[AXIS_Y] = mmc35240_props_table[id][data->res].sens[AXIS_Y];
> > +	sens[AXIS_Z] = mmc35240_props_table[id][data->res].sens[AXIS_Z];
> >  
> > -	nfo = mmc35240_props_table[data->res].nfo;
> >  
> > -	switch (index) {
> > -	case AXIS_X:
> > -		*val = (raw[AXIS_X] - nfo) * 1000 / sens[AXIS_X];
> > -		break;
> > -	case AXIS_Y:
> > -		*val = (raw[AXIS_Y] - nfo) * 1000 / sens[AXIS_Y] -
> > -			(raw[AXIS_Z] - nfo)  * 1000 / sens[AXIS_Z];
> > -		break;
> > -	case AXIS_Z:
> > -		*val = (raw[AXIS_Y] - nfo) * 1000 / sens[AXIS_Y] +
> > -			(raw[AXIS_Z] - nfo) * 1000 / sens[AXIS_Z];
> > -		break;
> > +	nfo = mmc35240_props_table[id][data->res].nfo;
> > +
> > +	switch (id) {
> > +	case MMC35240:
> > +		ret = mmc35240_raw_to_mgauss(raw, sens, nfo, index, val);
> > +		if (ret < 0)
> > +			return ret;
> > +
> > +		/* apply OTP compensation */
> > +		*val = (*val) * data->axis_coef[index] /
> > +			data->axis_scale[index];
> > +
> > +		return 0;
> > +	case MMC34160:
> > +		return mmc34160_raw_to_mgauss(raw, sens, nfo, index, val);
> >  	default:
> >  		return -EINVAL;
> >  	}
> > -	/* apply OTP compensation */
> > -	*val = (*val) * data->axis_coef[index] / data->axis_scale[index];
> >  
> >  	return 0;
> >  }
> > @@ -367,7 +456,7 @@ static int mmc35240_read_raw(struct iio_dev *indio_dev,
> >  		mutex_unlock(&data->mutex);
> >  		if (ret < 0)
> >  			return ret;
> > -		ret = mmc35240_raw_to_mgauss(data, chan->address, buf, val);
> > +		ret = memsic_raw_to_mgauss(data, chan->address, buf, val);
> >  		if (ret < 0)
> >  			return ret;
> >  		return IIO_VAL_INT;
> > @@ -485,12 +574,27 @@ static const struct regmap_config mmc35240_regmap_config = {
> >  	.num_reg_defaults = ARRAY_SIZE(mmc35240_reg_defaults),
> >  };
> >  
> > +static const char *mmc35240_match_acpi_device(struct device *dev,
> > +					      enum mmc35240_chipset *chipset)
> > +{
> > +	const struct acpi_device_id *id;
> > +
> > +	id = acpi_match_device(dev->driver->acpi_match_table, dev);
> > +	if (!id)
> > +		return NULL;
> > +
> > +	*chipset = (enum mmc35240_chipset)id->driver_data;
> > +
> > +	return dev_name(dev);
> > +}
> > +
> >  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;
> > +	const char *name;
> >  	int ret;
> >  
> >  	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
> > @@ -509,11 +613,20 @@ static int mmc35240_probe(struct i2c_client *client,
> >  	data->regmap = regmap;
> >  	data->res = MMC35240_16_BITS_SLOW;
> >  
> > +	if (id) {
> > +		data->chipset = (enum mmc35240_chipset)(id->driver_data);
> > +		name = id->name;
> > +	} else if (ACPI_HANDLE(&client->dev)) {
> > +		name = mmc35240_match_acpi_device(&client->dev,
> > +						  &data->chipset);
> > +	} else
> > +		return -ENODEV;
> > +
> >  	mutex_init(&data->mutex);
> >  
> >  	indio_dev->dev.parent = &client->dev;
> >  	indio_dev->info = &mmc35240_info;
> > -	indio_dev->name = MMC35240_DRV_NAME;
> > +	indio_dev->name = name;
> >  	indio_dev->channels = mmc35240_channels;
> >  	indio_dev->num_channels = ARRAY_SIZE(mmc35240_channels);
> >  	indio_dev->modes = INDIO_DIRECT_MODE;
> > @@ -566,14 +679,16 @@ static const struct of_device_id mmc35240_of_match[] = {
> >  MODULE_DEVICE_TABLE(of, mmc35240_of_match);
> >  
> >  static const struct acpi_device_id mmc35240_acpi_match[] = {
> > -	{"MMC35240", 0},
> > +	{"MMC35240", MMC35240},
> > +	{"MMC34160", MMC34160},
> >  	{ },
> >  };
> >  MODULE_DEVICE_TABLE(acpi, mmc35240_acpi_match);
> >  
> >  static const struct i2c_device_id mmc35240_id[] = {
> > -	{"mmc35240", 0},
> > -	{}
> > +	{"mmc35240", MMC35240},
> > +	{"mmc34160", MMC34160},
> > +	{ }
> >  };
> >  MODULE_DEVICE_TABLE(i2c, mmc35240_id);
> >  
> > 
> 
> -- 
> 
> Peter Meerwald
> +43-664-2444418 (mobile)
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