Re: [PATCH 3/3] iio: mpl3115: add support for sampling frequency

[David Lechner <dlechner@baylibre.com>]

On 9/21/25 8:33 AM, Antoni Pokusinski wrote:
> When the device is in ACTIVE mode the temperature and pressure measurements
> are collected with a frequency determined by the ST[3:0] bits of CTRL_REG2
> register.
> 
> Signed-off-by: Antoni Pokusinski <apokusinski01@gmail.com>
> ---
>  drivers/iio/pressure/mpl3115.c | 80 ++++++++++++++++++++++++++++++++++
>  1 file changed, 80 insertions(+)
> 
> diff --git a/drivers/iio/pressure/mpl3115.c b/drivers/iio/pressure/mpl3115.c
> index cf34de8f0d7e..2f1860ca1f32 100644
> --- a/drivers/iio/pressure/mpl3115.c
> +++ b/drivers/iio/pressure/mpl3115.c
> @@ -28,6 +28,7 @@
>  #define MPL3115_INT_SOURCE 0x12
>  #define MPL3115_PT_DATA_CFG 0x13
>  #define MPL3115_CTRL_REG1 0x26
> +#define MPL3115_CTRL_REG2 0x27
>  #define MPL3115_CTRL_REG3 0x28
>  #define MPL3115_CTRL_REG4 0x29
>  #define MPL3115_CTRL_REG5 0x2a
> @@ -46,6 +47,8 @@
>  #define MPL3115_CTRL_ACTIVE BIT(0) /* continuous measurement */
>  #define MPL3115_CTRL_OS_258MS (BIT(5) | BIT(4)) /* 64x oversampling */
>  
> +#define MPL3115_CTRL_ST (BIT(3) | BIT(2) | BIT(1) | BIT(0))

Can be simplified with GENMASK(3, 0).

Would also be more clear to call it MPL3115_CTRL_REG2_ST.
Otherwise it looks like it overlaps with the bits above
and below.

> +
>  #define MPL3115_CTRL_IPOL1 BIT(5)
>  #define MPL3115_CTRL_IPOL2 BIT(1)
>  
> @@ -53,6 +56,25 @@
>  
>  #define MPL3115_CTRL_INT_CFG_DRDY BIT(7)
>  
> +static const unsigned int mpl3115_samp_freq_table[][2] = {
> +	{ 1,      0},
> +	{ 0, 500000},
> +	{ 0, 250000},
> +	{ 0, 125000},
> +	{ 0,  62500},
> +	{ 0,  31250},
> +	{ 0,  15625},
> +	{ 0,   7812},
> +	{ 0,   3906},
> +	{ 0,   1953},
> +	{ 0,    976},
> +	{ 0,    488},
> +	{ 0,    244},
> +	{ 0,    122},
> +	{ 0,     61},
> +	{ 0,     30},

Didn't check these all, but got 30.5... for the last one, which
would round to 31. Not that it matters much in this case. ;-)

> +};
> +
>  struct mpl3115_data {
>  	struct i2c_client *client;
>  	struct iio_trigger *drdy_trig;
> @@ -163,10 +185,60 @@ static int mpl3115_read_raw(struct iio_dev *indio_dev,
>  		default:
>  			return -EINVAL;
>  		}
> +	case IIO_CHAN_INFO_SAMP_FREQ:
> +		ret = i2c_smbus_read_byte_data(data->client, MPL3115_CTRL_REG2);
> +		if (ret < 0)
> +			return ret;
> +
> +		ret &= MPL3115_CTRL_ST;

FIELD_GET() would be appropriate here.

> +
> +		*val = mpl3115_samp_freq_table[ret][0];
> +		*val2 = mpl3115_samp_freq_table[ret][1];
> +		return IIO_VAL_INT_PLUS_MICRO;
>  	}
>  	return -EINVAL;
>  }
>  
> +static int mpl3115_read_avail(struct iio_dev *indio_dev,
> +			      struct iio_chan_spec const *chan,
> +			      const int **vals, int *type, int *length,
> +			      long mask)
> +{
> +	if (mask != IIO_CHAN_INFO_SAMP_FREQ)
> +		return -EINVAL;
> +
> +	*type = IIO_VAL_INT_PLUS_MICRO;
> +	*length = ARRAY_SIZE(mpl3115_samp_freq_table) * 2;
> +	*vals = (int *)mpl3115_samp_freq_table;
> +	return IIO_AVAIL_LIST;
> +}
> +
> +static int mpl3115_write_raw(struct iio_dev *indio_dev,
> +			     const struct iio_chan_spec *chan,
> +			     int val, int val2, long mask)
> +{
> +	struct mpl3115_data *data = iio_priv(indio_dev);
> +	int i, ret;
> +
> +	if (mask != IIO_CHAN_INFO_SAMP_FREQ)
> +		return -EINVAL;
> +
> +	for (i = 0; i < ARRAY_SIZE(mpl3115_samp_freq_table); i++)
> +		if (val == mpl3115_samp_freq_table[i][0] &&
> +		    val2 == mpl3115_samp_freq_table[i][1])
> +			break;
> +
> +	if (i == ARRAY_SIZE(mpl3115_samp_freq_table))
> +		return -EINVAL;
> +
> +	if (!iio_device_claim_direct(indio_dev))
> +		return -EBUSY;
> +
> +	ret = i2c_smbus_write_byte_data(data->client, MPL3115_CTRL_REG2, i);

This potentially clears some unrelated bits. I guess it is not a problem for
now since those bit aren't used, but could be easy to overlook in the future.

Also, FIELD_PREP() would be appropriate.

> +	iio_device_release_direct(indio_dev);
> +	return ret;
> +}
> +
>  static irqreturn_t mpl3115_trigger_handler(int irq, void *p)
>  {
>  	struct iio_poll_func *pf = p;
> @@ -224,6 +296,9 @@ static const struct iio_chan_spec mpl3115_channels[] = {
>  		.type = IIO_PRESSURE,
>  		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
>  		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
> +		.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ),
> +		.info_mask_shared_by_all_available =
> +			BIT(IIO_CHAN_INFO_SAMP_FREQ),
>  		.scan_index = 0,
>  		.scan_type = {
>  			.sign = 'u',
> @@ -237,6 +312,9 @@ static const struct iio_chan_spec mpl3115_channels[] = {
>  		.type = IIO_TEMP,
>  		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
>  		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
> +		.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ),
> +		.info_mask_shared_by_all_available =
> +			BIT(IIO_CHAN_INFO_SAMP_FREQ),
>  		.scan_index = 1,
>  		.scan_type = {
>  			.sign = 's',
> @@ -307,6 +385,8 @@ static const struct iio_trigger_ops mpl3115_trigger_ops = {
>  
>  static const struct iio_info mpl3115_info = {
>  	.read_raw = &mpl3115_read_raw,
> +	.read_avail = &mpl3115_read_avail,
> +	.write_raw = &mpl3115_write_raw,
>  };
>  
>  static int mpl3115_trigger_probe(struct mpl3115_data *data,