Re: [PATCH] iio: imu: st_lsm6dsx: fix decimation factor estimation

[Jonathan Cameron <jic23@kernel.org>]

On Thu, 28 Nov 2019 17:55:18 +0200
Lorenzo Bianconi <lorenzo@kernel.org> wrote:

> Fix decimation factor and sip estimation for LSM6DSM series
> (max value for decimation factor is 32).
> If gyro and accel sensors are enabled at 12.5Hz and 416Hz
> respectively, decimation factor lookup will fail, producing
> unaligned data.

I'll confess I don't really follow how those values make sense
(as opposed to 13Hz) but I'm sure they do :)

> Remove unused decimator filed in st_lsm6dsx_sensor structure.
> 
> Fixes: f8710f0357bc ("iio: imu: st_lsm6dsx: express odr in mHZ")
> Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Applied to the fixes-togreg branch of iio.git.

Thanks,

Jonathan

> ---
>  drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h       |  2 --
>  .../iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c    | 25 +++++++++++++------
>  2 files changed, 18 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
> index b54aefcdaad4..dc55d7dff3eb 100644
> --- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
> +++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
> @@ -320,7 +320,6 @@ enum st_lsm6dsx_fifo_mode {
>   * @odr: Output data rate of the sensor [Hz].
>   * @watermark: Sensor watermark level.
>   * @sip: Number of samples in a given pattern.
> - * @decimator: FIFO decimation factor.
>   * @ts_ref: Sensor timestamp reference for hw one.
>   * @ext_info: Sensor settings if it is connected to i2c controller
>   */
> @@ -334,7 +333,6 @@ struct st_lsm6dsx_sensor {
>  
>  	u16 watermark;
>  	u8 sip;
> -	u8 decimator;
>  	s64 ts_ref;
>  
>  	struct {
> diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
> index bfd4c6306c0b..cb536b81a1c2 100644
> --- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
> +++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
> @@ -78,14 +78,20 @@ struct st_lsm6dsx_decimator_entry st_lsm6dsx_decimator_table[] = {
>  	{ 32, 0x7 },
>  };
>  
> -static int st_lsm6dsx_get_decimator_val(u8 val)
> +static int
> +st_lsm6dsx_get_decimator_val(struct st_lsm6dsx_sensor *sensor, u32 max_odr)
>  {
>  	const int max_size = ARRAY_SIZE(st_lsm6dsx_decimator_table);
> +	u32 decimator =  max_odr / sensor->odr;
>  	int i;
>  
> -	for (i = 0; i < max_size; i++)
> -		if (st_lsm6dsx_decimator_table[i].decimator == val)
> +	if (decimator > 1)
> +		decimator = round_down(decimator, 2);
> +
> +	for (i = 0; i < max_size; i++) {
> +		if (st_lsm6dsx_decimator_table[i].decimator == decimator)
>  			break;
> +	}
>  
>  	return i == max_size ? 0 : st_lsm6dsx_decimator_table[i].val;
>  }
> @@ -111,6 +117,13 @@ static void st_lsm6dsx_get_max_min_odr(struct st_lsm6dsx_hw *hw,
>  	}
>  }
>  
> +static u8 st_lsm6dsx_get_sip(struct st_lsm6dsx_sensor *sensor, u32 min_odr)
> +{
> +	u8 sip = sensor->odr / min_odr;
> +
> +	return sip > 1 ? round_down(sip, 2) : sip;
> +}
> +
>  static int st_lsm6dsx_update_decimators(struct st_lsm6dsx_hw *hw)
>  {
>  	const struct st_lsm6dsx_reg *ts_dec_reg;
> @@ -131,12 +144,10 @@ static int st_lsm6dsx_update_decimators(struct st_lsm6dsx_hw *hw)
>  		sensor = iio_priv(hw->iio_devs[i]);
>  		/* update fifo decimators and sample in pattern */
>  		if (hw->enable_mask & BIT(sensor->id)) {
> -			sensor->sip = sensor->odr / min_odr;
> -			sensor->decimator = max_odr / sensor->odr;
> -			data = st_lsm6dsx_get_decimator_val(sensor->decimator);
> +			sensor->sip = st_lsm6dsx_get_sip(sensor, min_odr);
> +			data = st_lsm6dsx_get_decimator_val(sensor, max_odr);
>  		} else {
>  			sensor->sip = 0;
> -			sensor->decimator = 0;
>  			data = 0;
>  		}
>  		ts_sip = max_t(u16, ts_sip, sensor->sip);