Re: [PATCH v3 3/9] iio: adc: ti-ads1262: support per-channel sampling frequency

[David Lechner <dlechner@baylibre.com>]

On 8/7/26 10:58 PM, Kurt Borja wrote:
> Add per-channel sampling frequency support. The "available" attribute is
> assigned per-channel too, in order to eventually support per-filter
> availability.
> 
> Signed-off-by: Kurt Borja <kuurtb@gmail.com>
> ---
>  drivers/iio/adc/ti-ads1262.c | 159 ++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 158 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/adc/ti-ads1262.c b/drivers/iio/adc/ti-ads1262.c
> index d78e5e3ae13e..b3b7b1249102 100644
> --- a/drivers/iio/adc/ti-ads1262.c
> +++ b/drivers/iio/adc/ti-ads1262.c
> @@ -26,6 +26,7 @@
>  #include <linux/regulator/consumer.h>
>  #include <linux/spi/spi.h>
>  #include <linux/types.h>
> +#include <linux/units.h>
>  
>  #include <asm/byteorder.h>
>  
> @@ -148,6 +149,7 @@ enum {
>  	ADS1262_DR_14400_SPS,
>  	ADS1262_DR_19200_SPS,
>  	ADS1262_DR_38400_SPS,
> +	ADS1262_DR_COUNT,
>  };
>  

/* FIR filter has limited data rate range. */
#define ADS1262_DR_COUNT_FIR_FILTER (ADS1262_DR_20_SPS + 1)

So we can properly restrict the rate when the FIR filter
is selected.

>  enum {
> @@ -173,6 +175,11 @@ struct ads1262_chip_info {
>  	const char *name;
>  };
>  
> +struct ads1262_channel {
> +	u8 data_rate;
> +	int samp_freqs[ADS1262_DR_COUNT][2];
> +};
> +
>  struct ads1262 {
>  	struct spi_device *spi;
>  	struct regmap *regmap;
> @@ -183,12 +190,47 @@ struct ads1262 {
>  	/* Protects channel state */
>  	struct mutex chan_lock;
>  	unsigned int num_channels;
> +	struct ads1262_channel *channels;
>  	struct completion drdy;
>  
>  	/* Protects transfer buffers and concurrent SPI transfers */
>  	struct mutex xfer_lock;
>  };
>  

Could use a comment to explain this is based on datasheet table
showing decimation ratios which correspond to the last two columns.

> +static const u32 ads1262_data_rate_div[] = {
> +	[ADS1262_DR_2_5_SPS]	= 8 * 64 * 5760,
> +	[ADS1262_DR_5_SPS]	= 8 * 64 * 2880,
> +	[ADS1262_DR_10_SPS]	= 8 * 64 * 1440,
> +	[ADS1262_DR_16_6_SPS]	= 8 * 64 * 864,
> +	[ADS1262_DR_20_SPS]	= 8 * 64 * 720,
> +	[ADS1262_DR_50_SPS]	= 8 * 64 * 288,
> +	[ADS1262_DR_60_SPS]	= 8 * 64 * 240,
> +	[ADS1262_DR_100_SPS]	= 8 * 64 * 144,
> +	[ADS1262_DR_400_SPS]	= 8 * 64 * 36,
> +	[ADS1262_DR_1200_SPS]	= 8 * 64 * 12,
> +	[ADS1262_DR_2400_SPS]	= 8 * 64 * 6,
> +	[ADS1262_DR_4800_SPS]	= 8 * 64 * 3,
> +	[ADS1262_DR_7200_SPS]	= 8 * 64 * 2,
> +	[ADS1262_DR_14400_SPS]	= 8 * 64 * 1,
> +	[ADS1262_DR_19200_SPS]	= 8 * 48 * 1,
> +	[ADS1262_DR_38400_SPS]	= 8 * 24 * 1,
> +};
> +
> +static int ads1262_find_two(const int (*array)[2], size_t num_elements, int val,
> +			    int val2)
> +{
> +	int i;
> +
> +	for (i = 0; i < num_elements; i++) {
> +		if (val == array[i][0] && val2 == array[i][1])
> +			break;

Just return i directly here.

> +	}
> +	if (i == num_elements)
> +		return -EINVAL;

Then can return directly here.

> +
> +	return i;
> +}
> +
>  static int ads1262_dev_cmd(struct ads1262 *st, u8 opcode)
>  {
>  	guard(mutex)(&st->xfer_lock);
> @@ -316,11 +358,19 @@ static int ads1262_wait_for_conversion(struct ads1262 *st)
>  static int ads1262_channel_enable(struct ads1262 *st,
>  				  const struct iio_chan_spec *spec)
>  {
> +	struct ads1262_channel *chan = &st->channels[spec->scan_index];
> +	int ret;
>  	u8 val;
>  
>  	guard(mutex)(&st->xfer_lock);
>  	guard(mutex)(&st->chan_lock);
>  
> +	val = FIELD_PREP(ADS1262_MODE2_DR_MASK, chan->data_rate);
> +	ret = regmap_update_bits(st->regmap, ADS1262_MODE2_REG,
> +				 ADS1262_MODE2_DR_MASK, val);
> +	if (ret)
> +		return ret;
> +
>  	val = FIELD_PREP(ADS1262_INPMUX_MUXN_MASK, spec->channel2) |
>  	      FIELD_PREP(ADS1262_INPMUX_MUXP_MASK, spec->channel);
>  	return regmap_update_bits(st->regmap, ADS1262_INPMUX_REG,
> @@ -372,6 +422,8 @@ static int ads1262_read_raw(struct iio_dev *indio_dev,
>  			    struct iio_chan_spec const *chan, int *val,
>  			    int *val2, long mask)
>  {
> +	struct ads1262 *st = iio_priv(indio_dev);
> +	struct ads1262_channel *chan_data = &st->channels[chan->scan_index];
>  	__be32 raw;
>  	int ret;
>  
> @@ -384,6 +436,65 @@ static int ads1262_read_raw(struct iio_dev *indio_dev,
>  
>  		return IIO_VAL_INT;
>  
> +	case IIO_CHAN_INFO_SAMP_FREQ: {
> +		guard(mutex)(&st->chan_lock);
> +
> +		*val = chan_data->samp_freqs[chan_data->data_rate][0];
> +		*val2 = chan_data->samp_freqs[chan_data->data_rate][1];
> +
> +		return IIO_VAL_INT_PLUS_MICRO;
> +	}
> +
> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +}
> +
> +static int ads1262_read_avail(struct iio_dev *indio_dev,
> +			      struct iio_chan_spec const *chan, const int **vals,
> +			      int *type, int *length, long mask)
> +{
> +	struct ads1262 *st = iio_priv(indio_dev);
> +	struct ads1262_channel *chan_data = &st->channels[chan->scan_index];
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_SAMP_FREQ:
> +		*type = IIO_VAL_INT_PLUS_MICRO;
> +		*vals = (const int *)chan_data->samp_freqs;
> +		*length = ARRAY_SIZE(chan_data->samp_freqs) * 2;

For now, this should be ADS1262_DR_COUNT_FIR_FILTER * 2 for now since
FIR filter is the default.

> +		return IIO_AVAIL_LIST;
> +
> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +}
> +
> +static int ads1262_write_raw(struct iio_dev *indio_dev,
> +			     struct iio_chan_spec const *chan, int val,
> +			     int val2, long mask)
> +{
> +	struct ads1262 *st = iio_priv(indio_dev);
> +	struct ads1262_channel *chan_data = &st->channels[chan->scan_index];
> +	int ret;
> +
> +	IIO_DEV_ACQUIRE_DIRECT_MODE(indio_dev, claim);
> +	if (IIO_DEV_ACQUIRE_FAILED(claim))
> +		return -EBUSY;
> +
> +	guard(mutex)(&st->chan_lock);
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_SAMP_FREQ:
> +		ret = ads1262_find_two(chan_data->samp_freqs,
> +				       ARRAY_SIZE(chan_data->samp_freqs),

Likewise ADS1262_DR_COUNT_FIR_FILTER here too for now.

> +				       val, val2);
> +		if (ret < 0)
> +			return -EINVAL;

Just return ret;

> +
> +		chan_data->data_rate = ret;
> +
> +		return 0;
> +
>  	default:
>  		return -EOPNOTSUPP;
>  	}
> @@ -404,6 +515,8 @@ static int ads1262_debugfs_reg_access(struct iio_dev *indio_dev, unsigned int re
>  
>  static const struct iio_info ads1262_iio_info = {
>  	.read_raw = ads1262_read_raw,
> +	.read_avail = ads1262_read_avail,
> +	.write_raw = ads1262_write_raw,
>  	.debugfs_reg_access = ads1262_debugfs_reg_access,
>  };
>  
> @@ -575,6 +688,36 @@ static const struct regmap_bus ads1262_regmap_bus = {
>  	.max_raw_write = ADS1262_MAX_REGMAP_WRITE,
>  };
>  
> +static void ads1262_populate_samp_freqs(struct ads1262 *st,
> +					struct ads1262_channel *chan)
> +{
> +	int freq_Hz, freq_rem;

Shouldn't these be u64 and u32?

> +	u64 freq_uHz;
> +
> +	for (unsigned int i = 0; i < ARRAY_SIZE(chan->samp_freqs); i++) {
> +		freq_uHz = div_u64(mul_u32_u32(st->clk_rate, MICRO),
> +				   ads1262_data_rate_div[i]);
> +		freq_Hz = div_u64_rem(freq_uHz, MICRO, &freq_rem);
> +
> +		chan->samp_freqs[i][0] = freq_Hz;
> +		chan->samp_freqs[i][1] = freq_rem;
> +	}
> +}
> +
> +static int ads1262_populate_tables(struct iio_dev *indio_dev)
> +{
> +	struct ads1262 *st = iio_priv(indio_dev);
> +	struct ads1262_channel *chan;
> +
> +	for (unsigned int i = 0; i < st->num_channels; i++) {
> +		chan = &st->channels[i];
> +
> +		ads1262_populate_samp_freqs(st, chan);
> +	}
> +
> +	return 0;
> +}
> +
>  static int ads1262_gpio_setup(struct ads1262 *st)
>  {
>  	struct device *dev = &st->spi->dev;
> @@ -661,6 +804,11 @@ static int ads1262_parse_channels(struct iio_dev *indio_dev)
>  	if (st->num_channels > ADS1262_MAX_CHANNEL_COUNT)
>  		return dev_err_probe(dev, -EINVAL, "too many channels\n");
>  
> +	st->channels = devm_kcalloc(dev, st->num_channels, sizeof(*st->channels),
> +				    GFP_KERNEL);
> +	if (!st->channels)
> +		return -ENOMEM;
> +
>  	/* Account for the timestamp channel */
>  	num_specs = st->num_channels + 1;
>  	specs = devm_kcalloc(dev, num_specs, sizeof(*specs), GFP_KERNEL);
> @@ -681,6 +829,8 @@ static int ads1262_parse_channels(struct iio_dev *indio_dev)
>  			return dev_err_probe(dev, -EINVAL, "%s: duplicated channel reg\n",
>  					     fwnode_get_name(node));
>  
> +		st->channels[reg].data_rate = ADS1262_DR_20_SPS;
> +
>  		specs[reg].scan_index = reg;
>  		specs[reg].scan_type = (struct iio_scan_type) {
>  			.format = IIO_SCAN_FORMAT_SIGNED_INT,
> @@ -701,7 +851,10 @@ static int ads1262_parse_channels(struct iio_dev *indio_dev)
>  		if (specs[reg].channel != ADS1262_INPMUX_TEMP)
>  			specs[reg].indexed = true;
>  
> -		specs[reg].info_mask_separate = BIT(IIO_CHAN_INFO_RAW);
> +		specs[reg].info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
> +						BIT(IIO_CHAN_INFO_SAMP_FREQ);
> +		specs[reg].info_mask_separate_available =
> +				BIT(IIO_CHAN_INFO_SAMP_FREQ);
>  	}
>  
>  	specs[num_specs - 1] = IIO_CHAN_SOFT_TIMESTAMP(num_specs - 1);
> @@ -786,6 +939,10 @@ static int ads1262_spi_probe(struct spi_device *spi)
>  	if (ret)
>  		return ret;
>  
> +	ret = ads1262_populate_tables(indio_dev);
> +	if (ret)
> +		return ret;
> +
>  	st->regmap = devm_regmap_init(dev, &ads1262_regmap_bus, st,
>  				      &ads1262_regmap_config);
>  	if (IS_ERR(st->regmap))
>