Re: [PATCH v2] iio: imu: st_lsm6dsx: set 10ms as min shub slave timeout

[Jonathan Cameron <jic23@kernel.org>]

On Sun,  1 Nov 2020 17:21:18 +0100
Lorenzo Bianconi <lorenzo@kernel.org> wrote:

> Set 10ms as minimum i2c slave configuration timeout since st_lsm6dsx
> relies on accel ODR for i2c master clock and at high sample rates
> (e.g. 833Hz or 416Hz) the slave sensor occasionally may need more cycles
> than i2c master timeout (2s/833Hz + 1 ~ 3ms) to apply the configuration
> resulting in an uncomplete slave configuration and a constant reading
> from the i2c slave connected to st_lsm6dsx i2c master.
> 
> Fixes: 8f9a5249e3d9 ("iio: imu: st_lsm6dsx: enable 833Hz sample frequency for tagged sensors")
> Fixes: c91c1c844ebd ("iio: imu: st_lsm6dsx: add i2c embedded controller support")
> Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Applied and marked for stable.

Thanks,

Jonathan

> ---
> Changes since v1:
> - improve commit log
> - add missing Fixes tags
> ---
>  drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_shub.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_shub.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_shub.c
> index 8c8d8870ca07..99562ba85ee4 100644
> --- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_shub.c
> +++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_shub.c
> @@ -156,11 +156,13 @@ static const struct st_lsm6dsx_ext_dev_settings st_lsm6dsx_ext_dev_table[] = {
>  static void st_lsm6dsx_shub_wait_complete(struct st_lsm6dsx_hw *hw)
>  {
>  	struct st_lsm6dsx_sensor *sensor;
> -	u32 odr;
> +	u32 odr, timeout;
>  
>  	sensor = iio_priv(hw->iio_devs[ST_LSM6DSX_ID_ACC]);
>  	odr = (hw->enable_mask & BIT(ST_LSM6DSX_ID_ACC)) ? sensor->odr : 12500;
> -	msleep((2000000U / odr) + 1);
> +	/* set 10ms as minimum timeout for i2c slave configuration */
> +	timeout = max_t(u32, 2000000U / odr + 1, 10);
> +	msleep(timeout);
>  }
>  
>  /*