On Thu, 24 Oct 2024 10:16:57 +0200
Julien Stephan <jstephan@xxxxxxxxxxxx> wrote:
> The formula in the datasheet for oversampling time conversion seems to
> be valid when device is at full speed using the maximum number of SDO
> lines. The driver currently support only 1 SDO line. The formula will
The 'new or corrected' formula I assume not the one in the datasheet?
> produce larger delays than what is currently set, but some devices
> actually require it.
This series is I think backed up behind the fixes chasing through Greg's
trees so I'm being a little fussier than I might otherwise be (when I'd
maybe just change stuff whilst applying and ask you to check the result!)
Code here looks fine, just a comment on the comment dropped.
>
> Signed-off-by: Julien Stephan <jstephan@xxxxxxxxxxxx>
> ---
> drivers/iio/adc/ad7380.c | 19 ++++++++++++++-----
> 1 file changed, 14 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/iio/adc/ad7380.c b/drivers/iio/adc/ad7380.c
> index fb728570debe6432d5f991595cb35e9e7af8b740..d57e17f38925da5fb7c8a0a2320a21474ba04b37 100644
> --- a/drivers/iio/adc/ad7380.c
> +++ b/drivers/iio/adc/ad7380.c
> @@ -77,6 +77,12 @@
> #define T_CONVERT_X_NS 500 /* xth conversion start time (oversampling) */
> #define T_POWERUP_US 5000 /* Power up */
>
> +/*
> + * AD738x support several SDO lines to increase throughput, but driver currently
> + * supports only 1 SDO line (standard SPI transaction)
> + */
> +#define AD7380_NUM_SDO_LINES 1
> +
> struct ad7380_timing_specs {
> const unsigned int t_csh_ns; /* CS minimum high time */
> };
> @@ -649,7 +655,8 @@ static int ad7380_set_ch(struct ad7380_state *st, unsigned int ch)
>
> if (st->oversampling_ratio > 1)
> xfer.delay.value = T_CONVERT_0_NS +
> - T_CONVERT_X_NS * (st->oversampling_ratio - 1);
> + T_CONVERT_X_NS * (st->oversampling_ratio - 1) *
> + st->chip_info->num_simult_channels / AD7380_NUM_SDO_LINES;
>
> return spi_sync_transfer(st->spi, &xfer, 1);
> }
> @@ -667,12 +674,13 @@ static void ad7380_update_xfers(struct ad7380_state *st,
>
> /*
> * In the case of oversampling, conversion time is higher than in normal
> - * mode. Technically T_CONVERT_X_NS is lower for some chips, but we use
> - * the maximum value for simplicity for now.
> + * mode: t_convert = T_CONVERT_0_NS + T_CONVERT_X_NS*(x - 1)*num_channel/number_of_sdo_lines
> + * where x is the oversampling ratio
Could drop the comment as the code is pretty clear. Is the statement about T_CONVERT_X_NS
being the max value of supported chips worth keeping?
> */
> if (st->oversampling_ratio > 1)
> t_convert = T_CONVERT_0_NS + T_CONVERT_X_NS *
> - (st->oversampling_ratio - 1);
> + (st->oversampling_ratio - 1) *
> + st->chip_info->num_simult_channels / AD7380_NUM_SDO_LINES;
>
> if (st->seq) {
> xfer[0].delay.value = xfer[1].delay.value = t_convert;
> @@ -1021,7 +1029,8 @@ static int ad7380_init(struct ad7380_state *st, bool external_ref_en)
> /* SPI 1-wire mode */
> return regmap_update_bits(st->regmap, AD7380_REG_ADDR_CONFIG2,
> AD7380_CONFIG2_SDO,
> - FIELD_PREP(AD7380_CONFIG2_SDO, 1));
> + FIELD_PREP(AD7380_CONFIG2_SDO,
> + AD7380_NUM_SDO_LINES));
> }
>
> static int ad7380_probe(struct spi_device *spi)
>
