[PATCH v7 4/4] iio: adc: ltc2378: Enable triggered buffer data capture

From: Marcelo Schmitt

Date: Thu Jul 16 2026 - 17:12:26 EST

Enable users to run triggered data captures with LTC2378 and similar ADCs.

Reviewed-by: David Lechner <dlechner@xxxxxxxxxxxx>
Signed-off-by: Marcelo Schmitt <marcelo.schmitt@xxxxxxxxxx>
---
Change log v6 -> v7:
No changes in v7.

drivers/iio/adc/Kconfig | 1 +
drivers/iio/adc/ltc2378.c | 75 +++++++++++++++++++++++++++------------
2 files changed, 53 insertions(+), 23 deletions(-)

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 96df8453b826..6cf67f7a6eed 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -952,6 +952,7 @@ config LTC2378
select IIO_BUFFER
select IIO_BUFFER_DMA
select IIO_BUFFER_DMAENGINE
+ select IIO_TRIGGERED_BUFFER
select SPI_OFFLOAD
select SPI_OFFLOAD_TRIGGER_PWM
help
diff --git a/drivers/iio/adc/ltc2378.c b/drivers/iio/adc/ltc2378.c
index 7d29f021cb7b..25db69edee4d 100644
--- a/drivers/iio/adc/ltc2378.c
+++ b/drivers/iio/adc/ltc2378.c
@@ -6,6 +6,7 @@
* Author: Marcelo Schmitt <marcelo.schmitt@xxxxxxxxxx>
*/

+#include <linux/array_size.h>
#include <linux/bitops.h>
#include <linux/bits.h>
#include <linux/byteorder/generic.h>
@@ -32,6 +33,8 @@
#include <linux/iio/buffer.h>
#include <linux/iio/buffer-dmaengine.h>
#include <linux/iio/iio.h>
+#include <linux/iio/triggered_buffer.h>
+#include <linux/iio/trigger_consumer.h>
#include <linux/iio/types.h>

#define LTC2378_TDSDOBUSYL_NS 5
@@ -97,7 +100,7 @@
struct ltc2378_chip_info {
const char *name;
unsigned int internal_ref_uV;
- struct iio_chan_spec chan;
+ struct iio_chan_spec chan[2]; /* 1 physical chan + 1 timestamp chan */
struct iio_chan_spec offload_chan;
unsigned int max_sample_rate_Hz;
unsigned int tconv_ns;
@@ -138,7 +141,7 @@ struct ltc2378_state {
static const struct ltc2378_chip_info ltc2338_18_chip_info = {
.name = "ltc2338-18",
.internal_ref_uV = 2048000,
- .chan = LTC2378_BIPOLAR_DIFF_CHANNEL(18),
+ .chan = { LTC2378_BIPOLAR_DIFF_CHANNEL(18), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_BIPOLAR_DIFF_CHANNEL(18),
.max_sample_rate_Hz = 1 * HZ_PER_MHZ,
.tconv_ns = 527,
@@ -146,7 +149,7 @@ static const struct ltc2378_chip_info ltc2338_18_chip_info = {

static const struct ltc2378_chip_info ltc2364_16_chip_info = {
.name = "ltc2364-16",
- .chan = LTC2378_UNIPOLAR_DIFF_CHANNEL(16),
+ .chan = { LTC2378_UNIPOLAR_DIFF_CHANNEL(16), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_UNIPOLAR_DIFF_CHANNEL(16),
.max_sample_rate_Hz = 250 * HZ_PER_KHZ,
.tconv_ns = 3000,
@@ -154,7 +157,7 @@ static const struct ltc2378_chip_info ltc2364_16_chip_info = {

static const struct ltc2378_chip_info ltc2364_18_chip_info = {
.name = "ltc2364-18",
- .chan = LTC2378_UNIPOLAR_DIFF_CHANNEL(18),
+ .chan = { LTC2378_UNIPOLAR_DIFF_CHANNEL(18), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_UNIPOLAR_DIFF_CHANNEL(18),
.max_sample_rate_Hz = 250 * HZ_PER_KHZ,
.tconv_ns = 3000,
@@ -162,7 +165,7 @@ static const struct ltc2378_chip_info ltc2364_18_chip_info = {

static const struct ltc2378_chip_info ltc2367_16_chip_info = {
.name = "ltc2367-16",
- .chan = LTC2378_UNIPOLAR_DIFF_CHANNEL(16),
+ .chan = { LTC2378_UNIPOLAR_DIFF_CHANNEL(16), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_UNIPOLAR_DIFF_CHANNEL(16),
.max_sample_rate_Hz = 500 * HZ_PER_KHZ,
.tconv_ns = 1500,
@@ -170,7 +173,7 @@ static const struct ltc2378_chip_info ltc2367_16_chip_info = {

static const struct ltc2378_chip_info ltc2367_18_chip_info = {
.name = "ltc2367-18",
- .chan = LTC2378_UNIPOLAR_DIFF_CHANNEL(18),
+ .chan = { LTC2378_UNIPOLAR_DIFF_CHANNEL(18), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_UNIPOLAR_DIFF_CHANNEL(18),
.max_sample_rate_Hz = 500 * HZ_PER_KHZ,
.tconv_ns = 1500,
@@ -178,7 +181,7 @@ static const struct ltc2378_chip_info ltc2367_18_chip_info = {

static const struct ltc2378_chip_info ltc2368_16_chip_info = {
.name = "ltc2368-16",
- .chan = LTC2378_UNIPOLAR_DIFF_CHANNEL(16),
+ .chan = { LTC2378_UNIPOLAR_DIFF_CHANNEL(16), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_UNIPOLAR_DIFF_CHANNEL(16),
.max_sample_rate_Hz = 1 * HZ_PER_MHZ,
.tconv_ns = 527,
@@ -186,7 +189,7 @@ static const struct ltc2378_chip_info ltc2368_16_chip_info = {

static const struct ltc2378_chip_info ltc2368_18_chip_info = {
.name = "ltc2368-18",
- .chan = LTC2378_UNIPOLAR_DIFF_CHANNEL(18),
+ .chan = { LTC2378_UNIPOLAR_DIFF_CHANNEL(18), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_UNIPOLAR_DIFF_CHANNEL(18),
.max_sample_rate_Hz = 1 * HZ_PER_MHZ,
.tconv_ns = 527,
@@ -194,7 +197,7 @@ static const struct ltc2378_chip_info ltc2368_18_chip_info = {

static const struct ltc2378_chip_info ltc2369_18_chip_info = {
.name = "ltc2369-18",
- .chan = LTC2378_UNIPOLAR_DIFF_CHANNEL(18),
+ .chan = { LTC2378_UNIPOLAR_DIFF_CHANNEL(18), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_UNIPOLAR_DIFF_CHANNEL(18),
.max_sample_rate_Hz = 1600 * HZ_PER_KHZ,
.tconv_ns = 412,
@@ -202,7 +205,7 @@ static const struct ltc2378_chip_info ltc2369_18_chip_info = {

static const struct ltc2378_chip_info ltc2370_16_chip_info = {
.name = "ltc2370-16",
- .chan = LTC2378_UNIPOLAR_DIFF_CHANNEL(16),
+ .chan = { LTC2378_UNIPOLAR_DIFF_CHANNEL(16), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_UNIPOLAR_DIFF_CHANNEL(16),
.max_sample_rate_Hz = 2 * HZ_PER_MHZ,
.tconv_ns = 322,
@@ -210,7 +213,7 @@ static const struct ltc2378_chip_info ltc2370_16_chip_info = {

static const struct ltc2378_chip_info ltc2376_16_chip_info = {
.name = "ltc2376-16",
- .chan = LTC2378_BIPOLAR_DIFF_CHANNEL(16),
+ .chan = { LTC2378_BIPOLAR_DIFF_CHANNEL(16), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_BIPOLAR_DIFF_CHANNEL(16),
.max_sample_rate_Hz = 250 * HZ_PER_KHZ,
.tconv_ns = 3000,
@@ -218,7 +221,7 @@ static const struct ltc2378_chip_info ltc2376_16_chip_info = {

static const struct ltc2378_chip_info ltc2376_18_chip_info = {
.name = "ltc2376-18",
- .chan = LTC2378_BIPOLAR_DIFF_CHANNEL(18),
+ .chan = { LTC2378_BIPOLAR_DIFF_CHANNEL(18), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_BIPOLAR_DIFF_CHANNEL(18),
.max_sample_rate_Hz = 250 * HZ_PER_KHZ,
.tconv_ns = 3000,
@@ -226,7 +229,7 @@ static const struct ltc2378_chip_info ltc2376_18_chip_info = {

static const struct ltc2378_chip_info ltc2376_20_chip_info = {
.name = "ltc2376-20",
- .chan = LTC2378_BIPOLAR_DIFF_CHANNEL(20),
+ .chan = { LTC2378_BIPOLAR_DIFF_CHANNEL(20), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_BIPOLAR_DIFF_CHANNEL(20),
.max_sample_rate_Hz = 250 * HZ_PER_KHZ,
.tconv_ns = 3000,
@@ -234,7 +237,7 @@ static const struct ltc2378_chip_info ltc2376_20_chip_info = {

static const struct ltc2378_chip_info ltc2377_16_chip_info = {
.name = "ltc2377-16",
- .chan = LTC2378_BIPOLAR_DIFF_CHANNEL(16),
+ .chan = { LTC2378_BIPOLAR_DIFF_CHANNEL(16), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_BIPOLAR_DIFF_CHANNEL(16),
.max_sample_rate_Hz = 500 * HZ_PER_KHZ,
.tconv_ns = 1500,
@@ -242,7 +245,7 @@ static const struct ltc2378_chip_info ltc2377_16_chip_info = {

static const struct ltc2378_chip_info ltc2377_18_chip_info = {
.name = "ltc2377-18",
- .chan = LTC2378_BIPOLAR_DIFF_CHANNEL(18),
+ .chan = { LTC2378_BIPOLAR_DIFF_CHANNEL(18), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_BIPOLAR_DIFF_CHANNEL(18),
.max_sample_rate_Hz = 500 * HZ_PER_KHZ,
.tconv_ns = 1500,
@@ -250,7 +253,7 @@ static const struct ltc2378_chip_info ltc2377_18_chip_info = {

static const struct ltc2378_chip_info ltc2377_20_chip_info = {
.name = "ltc2377-20",
- .chan = LTC2378_BIPOLAR_DIFF_CHANNEL(20),
+ .chan = { LTC2378_BIPOLAR_DIFF_CHANNEL(20), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_BIPOLAR_DIFF_CHANNEL(20),
.max_sample_rate_Hz = 500 * HZ_PER_KHZ,
.tconv_ns = 1500,
@@ -258,7 +261,7 @@ static const struct ltc2378_chip_info ltc2377_20_chip_info = {

static const struct ltc2378_chip_info ltc2378_16_chip_info = {
.name = "ltc2378-16",
- .chan = LTC2378_BIPOLAR_DIFF_CHANNEL(16),
+ .chan = { LTC2378_BIPOLAR_DIFF_CHANNEL(16), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_BIPOLAR_DIFF_CHANNEL(16),
.max_sample_rate_Hz = 1 * HZ_PER_MHZ,
.tconv_ns = 527,
@@ -266,7 +269,7 @@ static const struct ltc2378_chip_info ltc2378_16_chip_info = {

static const struct ltc2378_chip_info ltc2378_18_chip_info = {
.name = "ltc2378-18",
- .chan = LTC2378_BIPOLAR_DIFF_CHANNEL(18),
+ .chan = { LTC2378_BIPOLAR_DIFF_CHANNEL(18), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_BIPOLAR_DIFF_CHANNEL(18),
.max_sample_rate_Hz = 1 * HZ_PER_MHZ,
.tconv_ns = 527,
@@ -274,7 +277,7 @@ static const struct ltc2378_chip_info ltc2378_18_chip_info = {

static const struct ltc2378_chip_info ltc2378_20_chip_info = {
.name = "ltc2378-20",
- .chan = LTC2378_BIPOLAR_DIFF_CHANNEL(20),
+ .chan = { LTC2378_BIPOLAR_DIFF_CHANNEL(20), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_BIPOLAR_DIFF_CHANNEL(20),
.max_sample_rate_Hz = 1 * HZ_PER_MHZ,
.tconv_ns = 675,
@@ -282,7 +285,7 @@ static const struct ltc2378_chip_info ltc2378_20_chip_info = {

static const struct ltc2378_chip_info ltc2379_18_chip_info = {
.name = "ltc2379-18",
- .chan = LTC2378_BIPOLAR_DIFF_CHANNEL(18),
+ .chan = { LTC2378_BIPOLAR_DIFF_CHANNEL(18), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_BIPOLAR_DIFF_CHANNEL(18),
.max_sample_rate_Hz = 1600 * HZ_PER_KHZ,
.tconv_ns = 412,
@@ -290,7 +293,7 @@ static const struct ltc2378_chip_info ltc2379_18_chip_info = {

static const struct ltc2378_chip_info ltc2380_16_chip_info = {
.name = "ltc2380-16",
- .chan = LTC2378_BIPOLAR_DIFF_CHANNEL(16),
+ .chan = { LTC2378_BIPOLAR_DIFF_CHANNEL(16), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_BIPOLAR_DIFF_CHANNEL(16),
.max_sample_rate_Hz = 2 * HZ_PER_MHZ,
.tconv_ns = 322,
@@ -309,6 +312,25 @@ static int ltc2378_convert_and_acquire(struct ltc2378_state *st)
return ret;
}

+static irqreturn_t ltc2378_trigger_handler(int irq, void *p)
+{
+ struct iio_poll_func *pf = p;
+ struct iio_dev *indio_dev = pf->indio_dev;
+ struct ltc2378_state *st = iio_priv(indio_dev);
+ int ret;
+
+ ret = ltc2378_convert_and_acquire(st);
+ if (ret < 0)
+ goto err_out;
+
+ iio_push_to_buffers_with_ts(indio_dev, &st->scan, sizeof(st->scan),
+ pf->timestamp);
+
+err_out:
+ iio_trigger_notify_done(indio_dev->trig);
+ return IRQ_HANDLED;
+}
+
static int ltc2378_channel_single_read(const struct iio_chan_spec *chan,
struct ltc2378_state *st, int *val)
{
@@ -697,8 +719,15 @@ static int ltc2378_probe(struct spi_device *spi)
/* Fall back to low speed usage when no SPI offload is available. */
if (ret == -ENODEV) {
indio_dev->info = &ltc2378_iio_info;
- indio_dev->channels = &st->info->chan;
- indio_dev->num_channels = 1;
+ indio_dev->channels = st->info->chan;
+ indio_dev->num_channels = ARRAY_SIZE(st->info->chan);
+
+ ret = devm_iio_triggered_buffer_setup(dev, indio_dev,
+ iio_pollfunc_store_time,
+ ltc2378_trigger_handler,
+ NULL);
+ if (ret)
+ return ret;
} else if (ret) {
return dev_err_probe(dev, ret, "failed to get offload\n");
} else {
--
2.53.0