Re: [PATCH 2/2] iio: mma8452: add freefall detection for Freescale's accelerometers

[Martin Kepplinger <martink@posteo.de>]

Am 2015-12-12 um 16:34 schrieb Jonathan Cameron:
> On 08/12/15 16:21, Martin Kepplinger wrote:
>> This adds freefall event detection to the supported devices. It adds
>> the in_accel_x&y&z_mag_falling_en iio event attribute, which activates
>> freefall mode.
>>
>> In freefall mode, the current acceleration magnitude (AND combination
>> of all axis values) is compared to the specified threshold.
>> If it falls under the threshold (in_accel_mag_falling_value),
>> the appropriate IIO event code is generated.
>>
>> The values of rising and falling versions of various sysfs files are
>> shared, which is compliant to the IIO specification.
>>
>> This is what the sysfs "events" directory for these devices looks
>> like after this change:
>>
>> -rw-r--r--    4096 Oct 23 08:45 in_accel_mag_falling_period
>> -rw-r--r--    4096 Oct 23 08:45 in_accel_mag_falling_value
>> -rw-r--r--    4096 Oct 23 08:45 in_accel_mag_rising_period
>> -rw-r--r--    4096 Oct 23 08:45 in_accel_mag_rising_value
>> -r--r--r--    4096 Oct 23 08:45 in_accel_scale
>> -rw-r--r--    4096 Oct 23 08:45 in_accel_x&y&z_mag_falling_en
>> -rw-r--r--    4096 Oct 23 08:45 in_accel_x_mag_rising_en
>> -rw-r--r--    4096 Oct 23 08:45 in_accel_y_mag_rising_en
>> -rw-r--r--    4096 Oct 23 08:45 in_accel_z_mag_rising_en
>>
>> Signed-off-by: Martin Kepplinger <martin.kepplinger@theobroma-systems.com>
>> Signed-off-by: Christoph Muellner <christoph.muellner@theobroma-systems.com>
> I think the read back of other events being enabled is broken by this.
> Otherwise a few other minor bits and bobs.
> 
> Jonathan
>> ---
>> Other combinations (x&y, x&z or y&z) might be added later. This is the most
>> useful for freefall detection.
>>
>>
>>  drivers/iio/accel/mma8452.c | 156 ++++++++++++++++++++++++++++++++++++++------
>>  1 file changed, 137 insertions(+), 19 deletions(-)
>>
>> diff --git a/drivers/iio/accel/mma8452.c b/drivers/iio/accel/mma8452.c
>> index 162bbef..c8ac88c 100644
>> --- a/drivers/iio/accel/mma8452.c
>> +++ b/drivers/iio/accel/mma8452.c
>> @@ -15,7 +15,7 @@
>>   *
>>   * 7-bit I2C slave address 0x1c/0x1d (pin selectable)
>>   *
>> - * TODO: orientation / freefall events, autosleep
>> + * TODO: orientation events, autosleep
>>   */
>>  
>>  #include <linux/module.h>
>> @@ -143,6 +143,14 @@ struct mma_chip_info {
>>  	u8 ev_count;
>>  };
>>  
>> +enum {
>> +	idx_x,
>> +	idx_y,
>> +	idx_z,
>> +	idx_ts,
>> +	idx_xyz,
>> +};
> I would have slightly prefered the change to this enum to have been
> done as a precursor patch as it would have lead to an easily checked
> step 1 followed by the interesting stuff in step 2.

I guess you're right and it would be easier to read.

>> +
>>  static int mma8452_drdy(struct mma8452_data *data)
>>  {
>>  	int tries = 150;
>> @@ -409,6 +417,46 @@ fail:
>>  	return ret;
>>  }
>>  
>> +static int mma8452_freefall_mode_enabled(struct mma8452_data *data)
>> +{
>> +	int val;
>> +	const struct mma_chip_info *chip = data->chip_info;
>> +
>> +	val = i2c_smbus_read_byte_data(data->client, chip->ev_cfg);
>> +	if (val < 0)
>> +		return val;
>> +
>> +	return !(val & MMA8452_FF_MT_CFG_OAE);
>> +}
>> +
>> +static int mma8452_set_freefall_mode(struct mma8452_data *data, u8 state)
>> +{
>> +	int val, ret;
>> +	const struct mma_chip_info *chip = data->chip_info;
>> +
>> +	val = i2c_smbus_read_byte_data(data->client, chip->ev_cfg);
>> +	if (val < 0)
>> +		return val;
>> +
>> +	if (state && !(mma8452_freefall_mode_enabled(data))) {
>> +		val |= BIT(idx_x + chip->ev_cfg_chan_shift);
>> +		val |= BIT(idx_y + chip->ev_cfg_chan_shift);
>> +		val |= BIT(idx_z + chip->ev_cfg_chan_shift);
>> +		val &= ~MMA8452_FF_MT_CFG_OAE;
>> +	} else if (!state && mma8452_freefall_mode_enabled(data)) {
>> +		val &= ~BIT(idx_x + chip->ev_cfg_chan_shift);
>> +		val &= ~BIT(idx_y + chip->ev_cfg_chan_shift);
>> +		val &= ~BIT(idx_z + chip->ev_cfg_chan_shift);
>> +		val |= MMA8452_FF_MT_CFG_OAE;
>> +	}
>> +
>> +	ret = mma8452_change_config(data, chip->ev_cfg, val);
>> +	if (ret)
>> +		return ret;
>> +
>> +	return 0;
>> +}
>> +
>>  static int mma8452_set_hp_filter_frequency(struct mma8452_data *data,
>>  					   int val, int val2)
>>  {
>> @@ -602,6 +650,11 @@ static int mma8452_read_event_config(struct iio_dev *indio_dev,
>>  	const struct mma_chip_info *chip = data->chip_info;
>>  	int ret;
>>  
>> +	switch (chan->channel2) {
>> +	case IIO_MOD_X_AND_Y_AND_Z:
>> +		return mma8452_freefall_mode_enabled(data);
>> +	}
>> +
>>  	ret = i2c_smbus_read_byte_data(data->client,
>>  				       data->chip_info->ev_cfg);
>>  	if (ret < 0)
> I may have missed something here, but I think the check for the other events
> being enabled needs updating as well.  We are using the same bits in the
> register afterall.

we are using the same bits but reading is not broken. Freefall-mode is
defined by one bit. If the user wants to read x&y&z status (which only
exists in FALLING), I check this bit. Only one mode (direction) can be
active which these devices.

Only the new part is added and everything else stays the same.

I can't disable the individual axis (events) in RISING direction while
x&y&z freefall is enabled in FALLING, but that's ok according to the iio
sysfs doc. (RISING basically is irrelevant then. the problem is, it
isn't really here; I only assume the user isn't interested).

So what I could (and probably should) do is, I could implement this: A
change to RISING has no affect, while x&y&z FALLING is enabled. This
way, x&y&z stays x&y&z, and can't become, say, x&y, just because the
user changed z in RISING (which _should_ have no effect).

> 
>> @@ -620,6 +673,11 @@ static int mma8452_write_event_config(struct iio_dev *indio_dev,
>>  	const struct mma_chip_info *chip = data->chip_info;
>>  	int val;
>>  
>> +	switch (chan->channel2) {
>> +	case IIO_MOD_X_AND_Y_AND_Z:
>> +		return mma8452_set_freefall_mode(data, state);
>> +	}
>> +
>>  	val = i2c_smbus_read_byte_data(data->client, chip->ev_cfg);
>>  	if (val < 0)
>>  		return val;
>> @@ -630,7 +688,6 @@ static int mma8452_write_event_config(struct iio_dev *indio_dev,
>>  		val &= ~BIT(chan->scan_index + chip->ev_cfg_chan_shift);
>>  
>>  	val |= chip->ev_cfg_ele;
>> -	val |= MMA8452_FF_MT_CFG_OAE;
>>  
>>  	return mma8452_change_config(data, chip->ev_cfg, val);
>>  }
>> @@ -639,12 +696,26 @@ static void mma8452_transient_interrupt(struct iio_dev *indio_dev)
>>  {
>>  	struct mma8452_data *data = iio_priv(indio_dev);
>>  	s64 ts = iio_get_time_ns();
>> -	int src;
>> +	int src, cfg;
>>  
>>  	src = i2c_smbus_read_byte_data(data->client, data->chip_info->ev_src);
>>  	if (src < 0)
>>  		return;
>>  
>> +	cfg = i2c_smbus_read_byte_data(data->client, data->chip_info->ev_cfg);
>> +	if (cfg < 0)
>> +		return;
> This strikes me as odd.  I'd assume ev_cfg could be cached and avoid the
> read here?  It's basically saying if we enable a free fall event all
> the individual ones are disabled... 

It is. And nothing is really cached here; we always read any status from
the device, consistently in this driver.

If freefall event is enabled, all others have to be disabled. This is a
hardware limitation. The device operates in a different mode when
freefall mode is enabled.

Please get back to me in case of doubt.

>> +
>> +	if (!(cfg & MMA8452_FF_MT_CFG_OAE)) {
>> +		iio_push_event(indio_dev,
>> +			       IIO_MOD_EVENT_CODE(IIO_ACCEL, 0,
>> +						  IIO_MOD_X_AND_Y_AND_Z,
>> +						  IIO_EV_TYPE_MAG,
>> +						  IIO_EV_DIR_FALLING),
>> +			       ts);
>> +		return;
>> +	}
>> +
>>  	if (src & data->chip_info->ev_src_xe)
>>  		iio_push_event(indio_dev,
>>  			       IIO_MOD_EVENT_CODE(IIO_ACCEL, 0, IIO_MOD_X,
>> @@ -738,6 +809,27 @@ static int mma8452_reg_access_dbg(struct iio_dev *indio_dev,
>>  	return 0;
>>  }
>>  
>> +static const struct iio_event_spec mma8452_freefall_event[] = {
>> +	{
>> +		.type = IIO_EV_TYPE_MAG,
>> +		.dir = IIO_EV_DIR_FALLING,
>> +		.mask_separate = BIT(IIO_EV_INFO_ENABLE),
>> +		.mask_shared_by_type = BIT(IIO_EV_INFO_VALUE) |
>> +					BIT(IIO_EV_INFO_PERIOD) |
>> +					BIT(IIO_EV_INFO_HIGH_PASS_FILTER_3DB)
>> +	},
>> +};
>> +
>> +static const struct iio_event_spec mma8652_freefall_event[] = {
>> +	{
>> +		.type = IIO_EV_TYPE_MAG,
>> +		.dir = IIO_EV_DIR_FALLING,
>> +		.mask_separate = BIT(IIO_EV_INFO_ENABLE),
>> +		.mask_shared_by_type = BIT(IIO_EV_INFO_VALUE) |
>> +					BIT(IIO_EV_INFO_PERIOD)
>> +	},
>> +};
>> +
>>  static const struct iio_event_spec mma8452_transient_event[] = {
>>  	{
>>  		.type = IIO_EV_TYPE_MAG,
>> @@ -774,6 +866,24 @@ static struct attribute_group mma8452_event_attribute_group = {
>>  	.attrs = mma8452_event_attributes,
>>  };
>>  
>> +#define MMA8452_FREEFALL_CHANNEL(modifier, idx) { \
>> +	.type = IIO_ACCEL, \
>> +	.modified = 1, \
>> +	.channel2 = modifier, \
>> +	.scan_index = idx, \
>> +	.event_spec = mma8452_freefall_event, \
>> +	.num_event_specs = ARRAY_SIZE(mma8452_freefall_event), \
>> +}
>> +
>> +#define MMA8652_FREEFALL_CHANNEL(modifier, idx) { \
>> +	.type = IIO_ACCEL, \
>> +	.modified = 1, \
>> +	.channel2 = modifier, \
>> +	.scan_index = idx, \
> This isn't a 'real' channel with data to push into the buffer,
> so I'd expect to see an scan_index of -1 to stop it appearing
> under there. Same for the other varients.

Yes, thanks (for all the reviewing)!

> 
>> +	.event_spec = mma8652_freefall_event, \
>> +	.num_event_specs = ARRAY_SIZE(mma8652_freefall_event), \
>> +}
>> +
>>  #define MMA8452_CHANNEL(axis, idx, bits) { \
>>  	.type = IIO_ACCEL, \
>>  	.modified = 1, \
>> @@ -816,31 +926,35 @@ static struct attribute_group mma8452_event_attribute_group = {
>>  }
>>  
>>  static const struct iio_chan_spec mma8452_channels[] = {
>> -	MMA8452_CHANNEL(X, 0, 12),
>> -	MMA8452_CHANNEL(Y, 1, 12),
>> -	MMA8452_CHANNEL(Z, 2, 12),
>> -	IIO_CHAN_SOFT_TIMESTAMP(3),
>> +	MMA8452_CHANNEL(X, idx_x, 12),
>> +	MMA8452_CHANNEL(Y, idx_y, 12),
>> +	MMA8452_CHANNEL(Z, idx_z, 12),
>> +	IIO_CHAN_SOFT_TIMESTAMP(idx_ts),
>> +	MMA8452_FREEFALL_CHANNEL(IIO_MOD_X_AND_Y_AND_Z, idx_xyz),
>>  };
>>  
>>  static const struct iio_chan_spec mma8453_channels[] = {
>> -	MMA8452_CHANNEL(X, 0, 10),
>> -	MMA8452_CHANNEL(Y, 1, 10),
>> -	MMA8452_CHANNEL(Z, 2, 10),
>> -	IIO_CHAN_SOFT_TIMESTAMP(3),
>> +	MMA8452_CHANNEL(X, idx_x, 10),
>> +	MMA8452_CHANNEL(Y, idx_y, 10),
>> +	MMA8452_CHANNEL(Z, idx_z, 10),
>> +	IIO_CHAN_SOFT_TIMESTAMP(idx_ts),
>> +	MMA8452_FREEFALL_CHANNEL(IIO_MOD_X_AND_Y_AND_Z, idx_xyz),
>>  };
>>  
>>  static const struct iio_chan_spec mma8652_channels[] = {
>> -	MMA8652_CHANNEL(X, 0, 12),
>> -	MMA8652_CHANNEL(Y, 1, 12),
>> -	MMA8652_CHANNEL(Z, 2, 12),
>> -	IIO_CHAN_SOFT_TIMESTAMP(3),
>> +	MMA8652_CHANNEL(X, idx_x, 12),
>> +	MMA8652_CHANNEL(Y, idx_y, 12),
>> +	MMA8652_CHANNEL(Z, idx_z, 12),
>> +	IIO_CHAN_SOFT_TIMESTAMP(idx_ts),
>> +	MMA8652_FREEFALL_CHANNEL(IIO_MOD_X_AND_Y_AND_Z, idx_xyz),
>>  };
>>  
>>  static const struct iio_chan_spec mma8653_channels[] = {
>> -	MMA8652_CHANNEL(X, 0, 10),
>> -	MMA8652_CHANNEL(Y, 1, 10),
>> -	MMA8652_CHANNEL(Z, 2, 10),
>> -	IIO_CHAN_SOFT_TIMESTAMP(3),
>> +	MMA8652_CHANNEL(X, idx_x, 10),
>> +	MMA8652_CHANNEL(Y, idx_y, 10),
>> +	MMA8652_CHANNEL(Z, idx_z, 10),
>> +	IIO_CHAN_SOFT_TIMESTAMP(idx_ts),
>> +	MMA8652_FREEFALL_CHANNEL(IIO_MOD_X_AND_Y_AND_Z, idx_xyz),
>>  };
>>  
>>  enum {
>> @@ -1183,6 +1297,10 @@ static int mma8452_probe(struct i2c_client *client,
>>  	if (ret < 0)
>>  		goto buffer_cleanup;
>>  
>> +	ret = mma8452_set_freefall_mode(data, 0);
>> +	if (ret)
>> +		return ret;
>> +
>>  	return 0;
>>  
>>  buffer_cleanup:
>>
>