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iio: adc: ltc2378: Add support for LTC2338-18

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LTC2338-18 is similar to LTC2378-18, differentiating from the already
supported part mainly on the embedment of an internal voltage reference and
addition of a resistor divider network connected to the input signal path.
Extend the device driver, handling the internal reference and input signal
attenuation, enabling it to also support LTC2338-18.

Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
Signed-off-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
This commit is contained in:
Marcelo Schmitt 2026-07-27 18:31:58 -03:00 committed by Jonathan Cameron
parent 54355e3b18
commit d9166f1a99
1 changed files with 45 additions and 2 deletions
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47
drivers/iio/adc/ltc2378.c
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@ -107,6 +107,8 @@
struct ltc2378_chip_info {
const char *name;
unsigned int internal_ref_uV;
struct u32_fract internal_div;
struct iio_chan_spec chan[2]; /* 1 physical chan + 1 timestamp chan */
struct iio_chan_spec offload_chan;
unsigned int max_sample_rate_Hz;
@ -145,6 +147,16 @@ struct ltc2378_state {
} scan __aligned(IIO_DMA_MINALIGN);
};
static const struct ltc2378_chip_info ltc2338_18_chip_info = {
.name = "ltc2338-18",
.internal_ref_uV = 2048000,
.internal_div = { .numerator = 5, .denominator = 2 },
.chan = { LTC2378_DIFF_CHANNEL(18), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_DIFF_CHANNEL(18),
.max_sample_rate_Hz = 1 * HZ_PER_MHZ,
.tconv_ns = 527,
};
static const struct ltc2378_chip_info ltc2364_16_chip_info = {
.name = "ltc2364-16",
.chan = { LTC2378_PSEUDO_DIFF_CHANNEL(16), IIO_CHAN_SOFT_TIMESTAMP(1) },
@ -382,8 +394,11 @@ static int ltc2378_read_raw(struct iio_dev *indio_dev,
return IIO_VAL_INT;
}
case IIO_CHAN_INFO_SCALE:
case IIO_CHAN_INFO_SCALE: {
struct u32_fract fract = st->info->internal_div;
*val = st->ref_uV / MILLI;
if (fract.numerator && fract.denominator)
*val = mult_frac(*val, fract.numerator, fract.denominator);
/*
* For all LTC2378-like devices, the amount of bits that express
* voltage magnitude depend on the polarity / output code format:
@ -396,6 +411,7 @@ static int ltc2378_read_raw(struct iio_dev *indio_dev,
*val2 = chan->scan_type.realbits;
return IIO_VAL_FRACTIONAL_LOG2;
}
case IIO_CHAN_INFO_SAMP_FREQ:
*val = st->cnv_Hz;
return IIO_VAL_INT;
@ -641,6 +657,28 @@ static const struct spi_offload_config ltc2378_offload_config = {
SPI_OFFLOAD_CAP_RX_STREAM_DMA,
};
static int ltc2378_refin_setup(struct device *dev, struct ltc2378_state *st)
{
int ret;
/*
* The internal reference buffer amplifies both the internal reference
* and REFIN by a factor of 2.
*/
ret = devm_regulator_get_enable_read_voltage(dev, "refin");
if (ret == -ENODEV) { /* refin is optional */
st->ref_uV = st->info->internal_ref_uV * 2;
return 0;
}
if (ret < 0)
return dev_err_probe(dev, ret, "failed to read refin regulator\n");
st->ref_uV = ret * 2;
return 0;
}
static int ltc2378_ref_setup(struct device *dev, struct ltc2378_state *st)
{
int ret;
@ -676,7 +714,10 @@ static int ltc2378_probe(struct spi_device *spi)
if (!st->info)
return -EINVAL;
ret = ltc2378_ref_setup(dev, st);
if (st->info->internal_ref_uV)
ret = ltc2378_refin_setup(dev, st);
else
ret = ltc2378_ref_setup(dev, st);
if (ret)
return ret;
@ -750,6 +791,7 @@ static int ltc2378_probe(struct spi_device *spi)
}
static const struct of_device_id ltc2378_of_match[] = {
{ .compatible = "adi,ltc2338-18", .data = &ltc2338_18_chip_info },
{ .compatible = "adi,ltc2364-16", .data = &ltc2364_16_chip_info },
{ .compatible = "adi,ltc2364-18", .data = &ltc2364_18_chip_info },
{ .compatible = "adi,ltc2367-16", .data = &ltc2367_16_chip_info },
@ -774,6 +816,7 @@ static const struct of_device_id ltc2378_of_match[] = {
MODULE_DEVICE_TABLE(of, ltc2378_of_match);
static const struct spi_device_id ltc2378_spi_id[] = {
{ .name = "ltc2338-18", .driver_data = (kernel_ulong_t)&ltc2338_18_chip_info },
{ .name = "ltc2364-16", .driver_data = (kernel_ulong_t)&ltc2364_16_chip_info },
{ .name = "ltc2364-18", .driver_data = (kernel_ulong_t)&ltc2364_18_chip_info },
{ .name = "ltc2367-16", .driver_data = (kernel_ulong_t)&ltc2367_16_chip_info },