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Date: Mon, 06 May 2024 10:20:15 +0200
From: Nuno Sá <noname.nuno@...il.com>
To: Julien Stephan <jstephan@...libre.com>, Lars-Peter Clausen
<lars@...afoo.de>, Michael Hennerich <Michael.Hennerich@...log.com>, Nuno
Sá <nuno.sa@...log.com>, David Lechner
<dlechner@...libre.com>, Jonathan Cameron <jic23@...nel.org>, Rob Herring
<robh@...nel.org>, Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Conor Dooley <conor+dt@...nel.org>, Liam Girdwood <lgirdwood@...il.com>,
Mark Brown <broonie@...nel.org>
Cc: kernel test robot <lkp@...el.com>, linux-iio@...r.kernel.org,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC v6 08/10] iio: adc: ad7380: add oversampling support
Hi Julien,
On Wed, 2024-05-01 at 16:55 +0200, Julien Stephan wrote:
> ad7380x(-4) parts are able to do oversampling to increase accuracy.
> They support 2 average modes: normal average and rolling overage.
> This commits focus on enabling normal average oversampling, which is the
> default one.
>
> Normal averaging involves taking a number of samples, adding them together,
> and dividing the result by the number of samples taken.
> This result is then output from the device. The sample data is cleared when
> the process completes. Because we need more samples to output a value,
> the data output rate decrease with the oversampling ratio.
>
> Signed-off-by: Julien Stephan <jstephan@...libre.com>
> ---
> drivers/iio/adc/ad7380.c | 115 ++++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 114 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iio/adc/ad7380.c b/drivers/iio/adc/ad7380.c
> index 020959759170..1e3869f5e48c 100644
> --- a/drivers/iio/adc/ad7380.c
> +++ b/drivers/iio/adc/ad7380.c
> @@ -88,7 +88,10 @@ struct ad7380_chip_info {
> .type = IIO_VOLTAGE, \
> .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | \
> ((diff) ? 0 : BIT(IIO_CHAN_INFO_OFFSET)), \
> - .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
> + .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) | \
> + BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO), \
> + .info_mask_shared_by_type_available = \
> + BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO), \
> .indexed = 1, \
> .differential = (diff), \
> .channel = (diff) ? (2 * (index)) : (index), \
> @@ -156,6 +159,16 @@ static const struct ad7380_timing_specs ad7380_4_timing = {
> .t_csh_ns = 20,
> };
>
> +/*
> + * Available oversampling ratios. The indices correspond
> + * with the bit value expected by the chip.
> + * The available ratios depend on the averaging mode,
> + * only normal averaging is supported for now
> + */
> +static const int ad7380_normal_average_oversampling_ratios[] = {
> + 1, 2, 4, 8, 16, 32,
> +};
> +
> static const struct ad7380_chip_info ad7380_chip_info = {
> .name = "ad7380",
> .channels = ad7380_channels,
> @@ -231,6 +244,7 @@ static const struct ad7380_chip_info ad7384_4_chip_info = {
> struct ad7380_state {
> const struct ad7380_chip_info *chip_info;
> struct spi_device *spi;
> + unsigned int oversampling_ratio;
nit: move this to the other 'unsigned int' fields...
> struct regmap *regmap;
> unsigned int vref_mv;
> unsigned int vcm_mv[MAX_NUM_CHANNELS];
> @@ -386,6 +400,12 @@ static int ad7380_read_direct(struct ad7380_state *st,
> };
> int ret;
>
> + /*
> + * In normal average oversampling we need to wait for multiple conversions
> to be done
> + */
> + if (st->oversampling_ratio > 1)
> + xfers[0].delay.value = T_CONVERT_NS + 500 * st-
> >oversampling_ratio;
> +
> ret = spi_sync_transfer(st->spi, xfers, ARRAY_SIZE(xfers));
> if (ret < 0)
> return ret;
> @@ -428,6 +448,91 @@ static int ad7380_read_raw(struct iio_dev *indio_dev,
> / st->vref_mv;
>
> return IIO_VAL_INT;
> + case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
> + *val = st->oversampling_ratio;
> +
> + return IIO_VAL_INT;
> + default:
> + return -EINVAL;
> + }
> +}
> +
> +static int ad7380_read_avail(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan,
> + const int **vals, int *type, int *length,
> + long mask)
> +{
> + switch (mask) {
> + case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
> + *vals = ad7380_normal_average_oversampling_ratios;
> + *length = ARRAY_SIZE(ad7380_normal_average_oversampling_ratios);
> + *type = IIO_VAL_INT;
> +
> + return IIO_AVAIL_LIST;
> + default:
> + return -EINVAL;
> + }
> +}
> +
> +/**
> + * check_osr - Check the oversampling ratio
> + * @available_ratio: available ratios's array
> + * @size: size of the available_ratio array
> + * ratio: ratio to check
> + *
> + * Check if ratio is present in @available_ratio. Check for exact match.
> + * @available_ratio is an array of the available ratios (depending on the
> oversampling mode).
> + * The indices must correspond with the bit value expected by the chip.
> + */
> +static inline int check_osr(const int *available_ratio, int size, int ratio)
Please name the function ad7380_check_osr(). Also, drop the inline... The compiler
should be smart enough to take of that for us.
> +{
> + int i;
> +
> + for (i = 0; i < size; i++) {
> + if (ratio == available_ratio[i])
> + return i;
> + }
> +
> + return -EINVAL;
> +}
> +
> +static int ad7380_write_raw(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan, int val,
> + int val2, long mask)
> +{
> + struct ad7380_state *st = iio_priv(indio_dev);
> + int ret, osr;
> +
> + switch (mask) {
> + case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
> + osr = check_osr(ad7380_normal_average_oversampling_ratios,
> + ARRAY_SIZE(ad7380_normal_average_oversampling_rati
> os),
> + val);
> +
> + if (osr < 0)
> + return osr;
> +
> + iio_device_claim_direct_scoped(return -EBUSY, indio_dev) {
> + ret = regmap_update_bits(st->regmap,
> AD7380_REG_ADDR_CONFIG1,
> + AD7380_CONFIG1_OSR,
> + FIELD_PREP(AD7380_CONFIG1_OSR,
> osr));
> +
> + if (ret)
> + return ret;
> +
> + st->oversampling_ratio = val;
> +
> + /*
> + * Perform a soft reset.
> + * This will flush the oversampling block and FIFO but
> will
> + * maintain the content of the configurable registers.
> + */
> + ret = regmap_update_bits(st->regmap,
> AD7380_REG_ADDR_CONFIG2,
> + AD7380_CONFIG2_RESET,
> + FIELD_PREP(AD7380_CONFIG2_RESET,
> +
> AD7380_CONFIG2_RESET_SOFT));
> + }
> + return 0;
return ret;
Or you may be asked to directly return in regmap_update_bits() and use unreachable()
here.
> default:
> return -EINVAL;
> }
> @@ -435,6 +540,8 @@ static int ad7380_read_raw(struct iio_dev *indio_dev,
>
> static const struct iio_info ad7380_info = {
> .read_raw = &ad7380_read_raw,
> + .read_avail = &ad7380_read_avail,
> + .write_raw = &ad7380_write_raw,
> .debugfs_reg_access = &ad7380_debugfs_reg_access,
> };
>
> @@ -458,6 +565,12 @@ static int ad7380_init(struct ad7380_state *st, struct
> regulator *vref)
> if (ret < 0)
> return ret;
>
> + /* Disable oversampling by default.
> + * This is the default value after reset,
> + * so just initialize internal data
> + */
Your comment block is not in accordance with coding style. checkpatch should complain
about this.
> + st->oversampling_ratio = 1;
> +
> /* SPI 1-wire mode */
> return regmap_update_bits(st->regmap, AD7380_REG_ADDR_CONFIG2,
> AD7380_CONFIG2_SDO,
>
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