| Message ID | 20241024-ad7380-add-adaq4380-4-support-v3-2-6a29bd0f79da@baylibre.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | ad7380: add adaq4370-4 and adaq4380-4 support | expand |
On Thu, 24 Oct 2024 10:16:57 +0200 Julien Stephan <jstephan@baylibre.com> 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@baylibre.com> > --- > 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) >
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 */ 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)
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 produce larger delays than what is currently set, but some devices actually require it. Signed-off-by: Julien Stephan <jstephan@baylibre.com> --- drivers/iio/adc/ad7380.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-)