Date:	Tue, 15 Dec 2015 17:43:48 +0100
From:	Martin Kepplinger <martink@...teo.de>
To:	Martin Kepplinger <martink@...teo.de>,
	Jonathan Cameron <jic23@...nel.org>, knaack.h@....de,
	lars@...afoo.de, pmeerw@...erw.net,
	christoph.muellner@...obroma-systems.com, mfuzzey@...keon.com
Cc:	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] iio: mma8452: add freefall detection for Freescale's
 accelerometers



On 2015-12-15 07:04, Martin Kepplinger wrote:
> 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@...obroma-systems.com>
>>> Signed-off-by: Christoph Muellner <christoph.muellner@...obroma-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).
> 

ok. freefall mode (x&y&z falling event) is broken, if the user changes
something in rising direction.

Either I support more stuff in falling direction and everything would
need updating here, or, what I'll do now, I fix this and really only
support x&y&z for falling.

I think this is what you meant and a second version of the patches is on
it's way. They should also be easier to read now!

>>
>>> @@ -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:
>>>
>>
> 
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