Re: [PATCH 2/2] iio: adc: ti-ads1015: add 10% to conversion wait time

[Akinobu Mita <akinobu.mita@gmail.com>]

2017-08-24 17:27 GMT+09:00 Ladislav Michl <ladis@linux-mips.org>:
> As user's guide "ADS1015EVM, ADS1115EVM, ADS1015EVM-PDK, ADS1115EVM-PDK
> User Guide (Rev. B)" (http://www.ti.com/lit/ug/sbau157b/sbau157b.pdf)
> states at page 16:
> "Note that both the ADS1115 and ADS1015 have internal clocks with a =C2=
=B110%
> accuracy. If performing FFT tests, frequencies may appear to be incorrect
> as a result of this tolerance range.", add those 10% to converion wait
> time.
>
> Cc: Daniel Baluta <daniel.baluta@gmail.com>
> Cc: Jonathan Cameron <jic23@kernel.org>
> Cc: Akinobu Mita <akinobu.mita@gmail.com>
> Signed-off-by: Ladislav Michl <ladis@linux-mips.org>
> ---
>  drivers/iio/adc/ti-ads1015.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/iio/adc/ti-ads1015.c b/drivers/iio/adc/ti-ads1015.c
> index 034e48566ab5..de8f44127fe2 100644
> --- a/drivers/iio/adc/ti-ads1015.c
> +++ b/drivers/iio/adc/ti-ads1015.c
> @@ -268,6 +268,7 @@ int ads1015_get_adc_result(struct ads1015_data *data,=
 int chan, int *val)
>                 dr_old =3D (old & ADS1015_CFG_DR_MASK) >> ADS1015_CFG_DR_=
SHIFT;
>                 conv_time =3D DIV_ROUND_UP(USEC_PER_SEC, data->data_rate[=
dr_old]);
>                 conv_time +=3D DIV_ROUND_UP(USEC_PER_SEC, data->data_rate=
[dr]);
> +               conv_time +=3D conv_time / 10;

A comment explaining why we need this line helps someone who read it
as you described in the commit log.

>                 usleep_range(conv_time, conv_time + 1);
>                 data->conv_invalid =3D false;
>         }
> --
> 2.11.0
>