* [PATCH v9 1/6] dt-bindings: iio: adc: Add ltc2378
2026-07-27 21:30 [PATCH v9 0/6] iio: adc: Add support for LTC2378 and similar ADCs Marcelo Schmitt
@ 2026-07-27 21:30 ` Marcelo Schmitt
2026-07-27 21:30 ` [PATCH v9 2/6] iio: adc: ltc2378: Add support for LTC2378-20 and similar ADCs Marcelo Schmitt
` (4 subsequent siblings)
5 siblings, 0 replies; 10+ messages in thread
From: Marcelo Schmitt @ 2026-07-27 21:30 UTC (permalink / raw)
To: linux-iio, devicetree, linux-kernel
Cc: jic23, nuno.sa, Michael.Hennerich, dlechner, andy, robh, krzk+dt,
conor+dt, julianbraha, marcelo.schmitt1, Conor Dooley
Document how to describe LTC2378-20 and similar ADCs in device tree.
Reviewed-by: David Lechner <dlechner@baylibre.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
---
Change log v8 -> v9:
No changes in device tree doc.
.../bindings/iio/adc/adi,ltc2378.yaml | 170 ++++++++++++++++++
MAINTAINERS | 7 +
2 files changed, 177 insertions(+)
create mode 100644 Documentation/devicetree/bindings/iio/adc/adi,ltc2378.yaml
diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ltc2378.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ltc2378.yaml
new file mode 100644
index 000000000000..33de1dc4c256
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/adc/adi,ltc2378.yaml
@@ -0,0 +1,170 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/adc/adi,ltc2378.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Analog Devices LTC2378 and similar Analog to Digital Converters
+
+maintainers:
+ - Marcelo Schmitt <marcelo.schmitt@analog.com>
+
+description: |
+ Analog Devices LTC2378 series of ADCs.
+ Specifications can be found at:
+ https://www.analog.com/media/en/technical-documentation/data-sheets/233818fa.pdf
+ https://www.analog.com/media/en/technical-documentation/data-sheets/236416fa.pdf
+ https://www.analog.com/media/en/technical-documentation/data-sheets/236418f.pdf
+ https://www.analog.com/media/en/technical-documentation/data-sheets/236716fa.pdf
+ https://www.analog.com/media/en/technical-documentation/data-sheets/236718f.pdf
+ https://www.analog.com/media/en/technical-documentation/data-sheets/236816f.pdf
+ https://www.analog.com/media/en/technical-documentation/data-sheets/236818f.pdf
+ https://www.analog.com/media/en/technical-documentation/data-sheets/236918fa.pdf
+ https://www.analog.com/media/en/technical-documentation/data-sheets/237016fa.pdf
+ https://www.analog.com/media/en/technical-documentation/data-sheets/237616fa.pdf
+ https://www.analog.com/media/en/technical-documentation/data-sheets/237618fa.pdf
+ https://www.analog.com/media/en/technical-documentation/data-sheets/237620fb.pdf
+ https://www.analog.com/media/en/technical-documentation/data-sheets/237716fa.pdf
+ https://www.analog.com/media/en/technical-documentation/data-sheets/237718fa.pdf
+ https://www.analog.com/media/en/technical-documentation/data-sheets/237720fb.pdf
+ https://www.analog.com/media/en/technical-documentation/data-sheets/237816fa.pdf
+ https://www.analog.com/media/en/technical-documentation/data-sheets/237818fa.pdf
+ https://www.analog.com/media/en/technical-documentation/data-sheets/237820fb.pdf
+ https://www.analog.com/media/en/technical-documentation/data-sheets/237918fb.pdf
+ https://www.analog.com/media/en/technical-documentation/data-sheets/238016fb.pdf
+
+$ref: /schemas/spi/spi-peripheral-props.yaml#
+
+properties:
+ compatible:
+ oneOf:
+ # Single compatible string match.
+ - enum:
+ - adi,ltc2338-18
+ - adi,ltc2364-16
+ - adi,ltc2364-18
+ - adi,ltc2376-16
+ - adi,ltc2376-18
+ - adi,ltc2376-20
+
+ # Low sample rate fallback for 16-bit unipolar sensors.
+ - items:
+ - enum:
+ - adi,ltc2370-16 # 2 MSPS
+ - adi,ltc2368-16 # 1 MSPS
+ - adi,ltc2367-16 # 500 kSPS
+ - const: adi,ltc2364-16 # fallback (250 kSPS)
+
+ # Low sample rate fallback for 18-bit unipolar sensors.
+ - items:
+ - enum:
+ - adi,ltc2369-18 # 1.6 MSPS
+ - adi,ltc2368-18 # 1 MSPS
+ - adi,ltc2367-18 # 500 kSPS
+ - const: adi,ltc2364-18 # fallback (250 kSPS)
+
+ # Low sample rate fallback for 16-bit bipolar sensors.
+ - items:
+ - enum:
+ - adi,ltc2380-16 # 2 MSPS
+ - adi,ltc2378-16 # 1 MSPS
+ - adi,ltc2377-16 # 500 kSPS
+ - const: adi,ltc2376-16 # fallback (250 kSPS)
+
+ # Low sample rate fallback for 18-bit bipolar sensors.
+ - items:
+ - enum:
+ - adi,ltc2379-18 # 1.6 MSPS
+ - adi,ltc2378-18 # 1 MSPS
+ - adi,ltc2377-18 # 500 kSPS
+ - const: adi,ltc2376-18 # fallback (250 kSPS)
+
+ # Low sample rate fallback for 20-bit bipolar sensors.
+ - items:
+ - enum:
+ - adi,ltc2378-20 # 1 MSPS
+ - adi,ltc2377-20 # 500 kSPS
+ - const: adi,ltc2376-20 # fallback (250 kSPS)
+
+ reg:
+ maxItems: 1
+
+ spi-max-frequency:
+ maximum: 100000000
+
+ vdd-supply:
+ description: A 2.5V supply that powers the chip (VDD).
+
+ ovdd-supply:
+ description:
+ A 1.71V to 5.25V supply that sets the logic level for digital interface.
+
+ ref-supply:
+ description:
+ Voltage reference input that determines the scale of ADC conversions.
+
+ refin-supply:
+ description:
+ Alternative voltage reference input.
+
+ cnv-gpios:
+ description:
+ When provided, this property indicates the GPIO that is connected to the
+ CNV pin.
+ maxItems: 1
+
+ pwms:
+ description: PWM signal connected to the CNV pin.
+ maxItems: 1
+
+ interrupts:
+ description:
+ Interrupt for signaling the completion of conversion results. The active
+ low signal provided on the BUSY pin asserts when ADC conversions finish.
+ maxItems: 1
+
+required:
+ - compatible
+ - reg
+ - vdd-supply
+ - ovdd-supply
+
+allOf:
+ # Except for LTC2338, all designs require a voltage reference input
+ - if:
+ properties:
+ compatible:
+ not:
+ contains:
+ enum:
+ - adi,ltc2338-18
+ then:
+ required:
+ - ref-supply
+ properties:
+ refin-supply: false
+ else:
+ properties:
+ ref-supply: false
+
+unevaluatedProperties: false
+
+examples:
+ - |
+ #include <dt-bindings/gpio/gpio.h>
+ #include <dt-bindings/interrupt-controller/irq.h>
+ spi {
+ #address-cells = <1>;
+ #size-cells = <0>;
+ adc@0 {
+ compatible = "adi,ltc2378-20", "adi,ltc2376-20";
+ reg = <0>;
+ spi-max-frequency = <71000000>;
+ vdd-supply = <&supply_2_5V>;
+ ovdd-supply = <&supply_3_3V>;
+ ref-supply = <&supply_5V>;
+ cnv-gpios = <&gpio0 88 GPIO_ACTIVE_HIGH>;
+ interrupts = <7 IRQ_TYPE_EDGE_FALLING>;
+ interrupt-parent = <&gpio>;
+ };
+ };
diff --git a/MAINTAINERS b/MAINTAINERS
index 2b1ec46c5919..f0ae26699c99 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15343,6 +15343,13 @@ S: Maintained
F: Documentation/devicetree/bindings/iio/dac/lltc,ltc1660.yaml
F: drivers/iio/dac/ltc1660.c
+LTC2378 IIO ADC DRIVER
+M: Marcelo Schmitt <marcelo.schmitt@analog.com>
+L: linux-iio@vger.kernel.org
+S: Supported
+W: https://ez.analog.com/linux-software-drivers
+F: Documentation/devicetree/bindings/iio/adc/adi,ltc2378.yaml
+
LTC2664 IIO DAC DRIVER
M: Michael Hennerich <michael.hennerich@analog.com>
M: Kim Seer Paller <kimseer.paller@analog.com>
--
2.53.0
^ permalink raw reply related [flat|nested] 10+ messages in thread* [PATCH v9 2/6] iio: adc: ltc2378: Add support for LTC2378-20 and similar ADCs
2026-07-27 21:30 [PATCH v9 0/6] iio: adc: Add support for LTC2378 and similar ADCs Marcelo Schmitt
2026-07-27 21:30 ` [PATCH v9 1/6] dt-bindings: iio: adc: Add ltc2378 Marcelo Schmitt
@ 2026-07-27 21:30 ` Marcelo Schmitt
2026-07-27 21:42 ` sashiko-bot
2026-07-27 21:31 ` [PATCH v9 3/6] iio: adc: ltc2378: Enable high-speed data capture Marcelo Schmitt
` (3 subsequent siblings)
5 siblings, 1 reply; 10+ messages in thread
From: Marcelo Schmitt @ 2026-07-27 21:30 UTC (permalink / raw)
To: linux-iio, devicetree, linux-kernel
Cc: jic23, nuno.sa, Michael.Hennerich, dlechner, andy, robh, krzk+dt,
conor+dt, julianbraha, marcelo.schmitt1, Andy Shevchenko
Support for LTC2378-20 and similar analog-to-digital converters.
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Reviewed-by: David Lechner <dlechner@baylibre.com>
Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
---
Change log v8 -> v9:
- Extracted LTC2338-18 support to a separate follow up patch.
MAINTAINERS | 1 +
drivers/iio/adc/Kconfig | 12 ++
drivers/iio/adc/Makefile | 1 +
drivers/iio/adc/ltc2378.c | 387 ++++++++++++++++++++++++++++++++++++++
4 files changed, 401 insertions(+)
create mode 100644 drivers/iio/adc/ltc2378.c
diff --git a/MAINTAINERS b/MAINTAINERS
index f0ae26699c99..25821b771692 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15349,6 +15349,7 @@ L: linux-iio@vger.kernel.org
S: Supported
W: https://ez.analog.com/linux-software-drivers
F: Documentation/devicetree/bindings/iio/adc/adi,ltc2378.yaml
+F: drivers/iio/adc/ltc2378.c
LTC2664 IIO DAC DRIVER
M: Michael Hennerich <michael.hennerich@analog.com>
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index d1b198cb8a80..220c6739a8f2 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -943,6 +943,18 @@ config LTC2309
This driver can also be built as a module. If so, the module will
be called ltc2309.
+config LTC2378
+ tristate "Analog Devices LTC2378 ADC driver"
+ depends on SPI
+ depends on REGULATOR || COMPILE_TEST
+ depends on GPIOLIB
+ help
+ Say yes here to build support for Analog Devices LTC2378-20 and
+ similar analog to digital converters.
+
+ This driver can also be built as a module. If so, the module will
+ be called ltc2378.
+
config LTC2471
tristate "Linear Technology LTC2471 and LTC2473 ADC driver"
depends on I2C
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 0f90b75577ff..6058a8be6ccd 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -81,6 +81,7 @@ obj-$(CONFIG_LP8788_ADC) += lp8788_adc.o
obj-$(CONFIG_LPC18XX_ADC) += lpc18xx_adc.o
obj-$(CONFIG_LPC32XX_ADC) += lpc32xx_adc.o
obj-$(CONFIG_LTC2309) += ltc2309.o
+obj-$(CONFIG_LTC2378) += ltc2378.o
obj-$(CONFIG_LTC2471) += ltc2471.o
obj-$(CONFIG_LTC2485) += ltc2485.o
obj-$(CONFIG_LTC2496) += ltc2496.o ltc2497-core.o
diff --git a/drivers/iio/adc/ltc2378.c b/drivers/iio/adc/ltc2378.c
new file mode 100644
index 000000000000..d161435fc3a3
--- /dev/null
+++ b/drivers/iio/adc/ltc2378.c
@@ -0,0 +1,387 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Analog Devices LTC2378 ADC series driver
+ *
+ * Copyright (C) 2026 Analog Devices Inc.
+ * Author: Marcelo Schmitt <marcelo.schmitt@analog.com>
+ */
+
+#include <linux/bitops.h>
+#include <linux/bits.h>
+#include <linux/byteorder/generic.h>
+#include <linux/cleanup.h>
+#include <linux/device.h>
+#include <linux/delay.h>
+#include <linux/device-id/spi.h>
+#include <linux/device-id/of.h>
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/regulator/consumer.h>
+#include <linux/spi/spi.h>
+#include <linux/types.h>
+#include <linux/units.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/types.h>
+
+#define LTC2378_MAX_DATA_WAIT_US 4 /* max(TBUSYLH + TCONV + TDSDOBUSYL) */
+
+#define LTC2378_CHANNEL(_sign, _real_bits, _storage_bits) \
+{ \
+ .type = IIO_VOLTAGE, \
+ .indexed = 1, \
+ .differential = _sign, \
+ .channel = 0, \
+ .channel2 = _sign ? 1 : 0, \
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | \
+ BIT(IIO_CHAN_INFO_SCALE), \
+ .scan_index = 0, \
+ .scan_type = { \
+ .format = _sign ? IIO_SCAN_FORMAT_SIGNED_INT : \
+ IIO_SCAN_FORMAT_UNSIGNED_INT, \
+ .realbits = _real_bits, \
+ .storagebits = _storage_bits, \
+ .shift = _storage_bits - _real_bits, \
+ .endianness = IIO_BE, \
+ }, \
+}
+
+#define LTC2378_DIFF_CHANNEL(_real_bits) \
+ LTC2378_CHANNEL(1, _real_bits, (((_real_bits) > 16) ? 32 : 16))
+
+#define LTC2378_PSEUDO_DIFF_CHANNEL(_real_bits) \
+ LTC2378_CHANNEL(0, _real_bits, (((_real_bits) > 16) ? 32 : 16))
+
+struct ltc2378_chip_info {
+ const char *name;
+ struct iio_chan_spec chan;
+};
+
+struct ltc2378_state {
+ const struct ltc2378_chip_info *info;
+ struct gpio_desc *cnv_gpio;
+ struct spi_device *spi;
+ struct mutex lock; /* Protect data acquisition cycle */
+ int ref_uV;
+ struct spi_transfer xfer;
+
+ /*
+ * DMA (thus cache coherency maintenance) requires the transfer buffers
+ * to live in their own cache lines.
+ */
+ struct {
+ union {
+ __be16 sample_buf16_be;
+ __be32 sample_buf32_be;
+ u16 sample_buf16;
+ u32 sample_buf32;
+ } data;
+ aligned_s64 timestamp;
+ } scan __aligned(IIO_DMA_MINALIGN);
+};
+
+static const struct ltc2378_chip_info ltc2364_16_chip_info = {
+ .name = "ltc2364-16",
+ .chan = LTC2378_PSEUDO_DIFF_CHANNEL(16),
+};
+
+static const struct ltc2378_chip_info ltc2364_18_chip_info = {
+ .name = "ltc2364-18",
+ .chan = LTC2378_PSEUDO_DIFF_CHANNEL(18),
+};
+
+static const struct ltc2378_chip_info ltc2367_16_chip_info = {
+ .name = "ltc2367-16",
+ .chan = LTC2378_PSEUDO_DIFF_CHANNEL(16),
+};
+
+static const struct ltc2378_chip_info ltc2367_18_chip_info = {
+ .name = "ltc2367-18",
+ .chan = LTC2378_PSEUDO_DIFF_CHANNEL(18),
+};
+
+static const struct ltc2378_chip_info ltc2368_16_chip_info = {
+ .name = "ltc2368-16",
+ .chan = LTC2378_PSEUDO_DIFF_CHANNEL(16),
+};
+
+static const struct ltc2378_chip_info ltc2368_18_chip_info = {
+ .name = "ltc2368-18",
+ .chan = LTC2378_PSEUDO_DIFF_CHANNEL(18),
+};
+
+static const struct ltc2378_chip_info ltc2369_18_chip_info = {
+ .name = "ltc2369-18",
+ .chan = LTC2378_PSEUDO_DIFF_CHANNEL(18),
+};
+
+static const struct ltc2378_chip_info ltc2370_16_chip_info = {
+ .name = "ltc2370-16",
+ .chan = LTC2378_PSEUDO_DIFF_CHANNEL(16),
+};
+
+static const struct ltc2378_chip_info ltc2376_16_chip_info = {
+ .name = "ltc2376-16",
+ .chan = LTC2378_DIFF_CHANNEL(16),
+};
+
+static const struct ltc2378_chip_info ltc2376_18_chip_info = {
+ .name = "ltc2376-18",
+ .chan = LTC2378_DIFF_CHANNEL(18),
+};
+
+static const struct ltc2378_chip_info ltc2376_20_chip_info = {
+ .name = "ltc2376-20",
+ .chan = LTC2378_DIFF_CHANNEL(20),
+};
+
+static const struct ltc2378_chip_info ltc2377_16_chip_info = {
+ .name = "ltc2377-16",
+ .chan = LTC2378_DIFF_CHANNEL(16),
+};
+
+static const struct ltc2378_chip_info ltc2377_18_chip_info = {
+ .name = "ltc2377-18",
+ .chan = LTC2378_DIFF_CHANNEL(18),
+};
+
+static const struct ltc2378_chip_info ltc2377_20_chip_info = {
+ .name = "ltc2377-20",
+ .chan = LTC2378_DIFF_CHANNEL(20),
+};
+
+static const struct ltc2378_chip_info ltc2378_16_chip_info = {
+ .name = "ltc2378-16",
+ .chan = LTC2378_DIFF_CHANNEL(16),
+};
+
+static const struct ltc2378_chip_info ltc2378_18_chip_info = {
+ .name = "ltc2378-18",
+ .chan = LTC2378_DIFF_CHANNEL(18),
+};
+
+static const struct ltc2378_chip_info ltc2378_20_chip_info = {
+ .name = "ltc2378-20",
+ .chan = LTC2378_DIFF_CHANNEL(20),
+};
+
+static const struct ltc2378_chip_info ltc2379_18_chip_info = {
+ .name = "ltc2379-18",
+ .chan = LTC2378_DIFF_CHANNEL(18),
+};
+
+static const struct ltc2378_chip_info ltc2380_16_chip_info = {
+ .name = "ltc2380-16",
+ .chan = LTC2378_DIFF_CHANNEL(16),
+};
+
+static int ltc2378_convert_and_acquire(struct ltc2378_state *st)
+{
+ int ret;
+
+ /* Cause a rising edge of CNV to initiate a new ADC conversion */
+ gpiod_set_value_cansleep(st->cnv_gpio, 1);
+ fsleep(LTC2378_MAX_DATA_WAIT_US);
+ ret = spi_sync_transfer(st->spi, &st->xfer, 1);
+ gpiod_set_value_cansleep(st->cnv_gpio, 0);
+
+ return ret;
+}
+
+static int ltc2378_channel_single_read(const struct iio_chan_spec *chan,
+ struct ltc2378_state *st, int *val)
+{
+ const struct iio_scan_type *scan_type = &chan->scan_type;
+ u32 sample;
+ int ret;
+
+ guard(mutex)(&st->lock);
+ ret = ltc2378_convert_and_acquire(st);
+ if (ret)
+ return ret;
+
+ if (chan->scan_type.endianness == IIO_BE) {
+ if (chan->scan_type.realbits > 16)
+ sample = be32_to_cpu(st->scan.data.sample_buf32_be);
+ else
+ sample = be16_to_cpu(st->scan.data.sample_buf16_be);
+ } else { /* IIO_CPU */
+ if (chan->scan_type.realbits > 16)
+ sample = st->scan.data.sample_buf32;
+ else
+ sample = st->scan.data.sample_buf16;
+ }
+
+ sample >>= chan->scan_type.shift;
+
+ if (scan_type->format == IIO_SCAN_FORMAT_SIGNED_INT)
+ *val = sign_extend32(sample, scan_type->realbits - 1);
+ else
+ *val = sample;
+
+ return 0;
+}
+
+static int ltc2378_read_raw(struct iio_dev *indio_dev,
+ const struct iio_chan_spec *chan,
+ int *val, int *val2, long mask)
+{
+ struct ltc2378_state *st = iio_priv(indio_dev);
+ int ret;
+
+ switch (mask) {
+ case IIO_CHAN_INFO_RAW: {
+ IIO_DEV_ACQUIRE_DIRECT_MODE(indio_dev, claim);
+ if (IIO_DEV_ACQUIRE_FAILED(claim))
+ return -EBUSY;
+
+ ret = ltc2378_channel_single_read(chan, st, val);
+ if (ret)
+ return ret;
+
+ return IIO_VAL_INT;
+ }
+ case IIO_CHAN_INFO_SCALE:
+ *val = st->ref_uV / MILLI;
+ /*
+ * For all LTC2378-like devices, the amount of bits that express
+ * voltage magnitude depend on the polarity / output code format:
+ * - straight binary: All precision/resolution bits are used.
+ * - 2's complement: One of the precision bits is used for sign.
+ */
+ if (chan->scan_type.format == IIO_SCAN_FORMAT_SIGNED_INT)
+ *val2 = chan->scan_type.realbits - 1;
+ else
+ *val2 = chan->scan_type.realbits;
+
+ return IIO_VAL_FRACTIONAL_LOG2;
+
+ default:
+ return -EINVAL;
+ }
+}
+
+static const struct iio_info ltc2378_iio_info = {
+ .read_raw = <c2378_read_raw,
+};
+
+static int ltc2378_ref_setup(struct device *dev, struct ltc2378_state *st)
+{
+ int ret;
+
+ ret = devm_regulator_get_enable_read_voltage(dev, "ref");
+ if (ret < 0)
+ return dev_err_probe(dev, ret, "failed to read ref regulator\n");
+
+ st->ref_uV = ret;
+
+ return 0;
+}
+
+static int ltc2378_probe(struct spi_device *spi)
+{
+ struct device *dev = &spi->dev;
+ struct iio_dev *indio_dev;
+ struct ltc2378_state *st;
+ int ret;
+
+ indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
+ if (!indio_dev)
+ return -ENOMEM;
+
+ st = iio_priv(indio_dev);
+ st->spi = spi;
+
+ ret = devm_mutex_init(dev, &st->lock);
+ if (ret)
+ return ret;
+
+ st->info = spi_get_device_match_data(spi);
+ if (!st->info)
+ return -EINVAL;
+
+ ret = ltc2378_ref_setup(dev, st);
+ if (ret)
+ return ret;
+
+ indio_dev->name = st->info->name;
+ indio_dev->info = <c2378_iio_info;
+ indio_dev->modes = INDIO_DIRECT_MODE;
+
+ st->cnv_gpio = devm_gpiod_get(dev, "cnv", GPIOD_OUT_LOW);
+ if (IS_ERR(st->cnv_gpio))
+ return dev_err_probe(dev, PTR_ERR(st->cnv_gpio),
+ "failed to get CNV GPIO");
+
+ indio_dev->channels = &st->info->chan;
+ indio_dev->num_channels = 1;
+
+ st->xfer.rx_buf = &st->scan.data;
+ st->xfer.len = spi_bpw_to_bytes(indio_dev->channels[0].scan_type.realbits);
+
+ return devm_iio_device_register(&spi->dev, indio_dev);
+}
+
+static const struct of_device_id ltc2378_of_match[] = {
+ { .compatible = "adi,ltc2364-16", .data = <c2364_16_chip_info },
+ { .compatible = "adi,ltc2364-18", .data = <c2364_18_chip_info },
+ { .compatible = "adi,ltc2367-16", .data = <c2367_16_chip_info },
+ { .compatible = "adi,ltc2367-18", .data = <c2367_18_chip_info },
+ { .compatible = "adi,ltc2368-16", .data = <c2368_16_chip_info },
+ { .compatible = "adi,ltc2368-18", .data = <c2368_18_chip_info },
+ { .compatible = "adi,ltc2369-18", .data = <c2369_18_chip_info },
+ { .compatible = "adi,ltc2370-16", .data = <c2370_16_chip_info },
+ { .compatible = "adi,ltc2376-16", .data = <c2376_16_chip_info },
+ { .compatible = "adi,ltc2376-18", .data = <c2376_18_chip_info },
+ { .compatible = "adi,ltc2376-20", .data = <c2376_20_chip_info },
+ { .compatible = "adi,ltc2377-16", .data = <c2377_16_chip_info },
+ { .compatible = "adi,ltc2377-18", .data = <c2377_18_chip_info },
+ { .compatible = "adi,ltc2377-20", .data = <c2377_20_chip_info },
+ { .compatible = "adi,ltc2378-16", .data = <c2378_16_chip_info },
+ { .compatible = "adi,ltc2378-18", .data = <c2378_18_chip_info },
+ { .compatible = "adi,ltc2378-20", .data = <c2378_20_chip_info },
+ { .compatible = "adi,ltc2379-18", .data = <c2379_18_chip_info },
+ { .compatible = "adi,ltc2380-16", .data = <c2380_16_chip_info },
+ { }
+};
+MODULE_DEVICE_TABLE(of, ltc2378_of_match);
+
+static const struct spi_device_id ltc2378_spi_id[] = {
+ { .name = "ltc2364-16", .driver_data = (kernel_ulong_t)<c2364_16_chip_info },
+ { .name = "ltc2364-18", .driver_data = (kernel_ulong_t)<c2364_18_chip_info },
+ { .name = "ltc2367-16", .driver_data = (kernel_ulong_t)<c2367_16_chip_info },
+ { .name = "ltc2367-18", .driver_data = (kernel_ulong_t)<c2367_18_chip_info },
+ { .name = "ltc2368-16", .driver_data = (kernel_ulong_t)<c2368_16_chip_info },
+ { .name = "ltc2368-18", .driver_data = (kernel_ulong_t)<c2368_18_chip_info },
+ { .name = "ltc2369-18", .driver_data = (kernel_ulong_t)<c2369_18_chip_info },
+ { .name = "ltc2370-16", .driver_data = (kernel_ulong_t)<c2370_16_chip_info },
+ { .name = "ltc2376-16", .driver_data = (kernel_ulong_t)<c2376_16_chip_info },
+ { .name = "ltc2376-18", .driver_data = (kernel_ulong_t)<c2376_18_chip_info },
+ { .name = "ltc2376-20", .driver_data = (kernel_ulong_t)<c2376_20_chip_info },
+ { .name = "ltc2377-16", .driver_data = (kernel_ulong_t)<c2377_16_chip_info },
+ { .name = "ltc2377-18", .driver_data = (kernel_ulong_t)<c2377_18_chip_info },
+ { .name = "ltc2377-20", .driver_data = (kernel_ulong_t)<c2377_20_chip_info },
+ { .name = "ltc2378-16", .driver_data = (kernel_ulong_t)<c2378_16_chip_info },
+ { .name = "ltc2378-18", .driver_data = (kernel_ulong_t)<c2378_18_chip_info },
+ { .name = "ltc2378-20", .driver_data = (kernel_ulong_t)<c2378_20_chip_info },
+ { .name = "ltc2379-18", .driver_data = (kernel_ulong_t)<c2379_18_chip_info },
+ { .name = "ltc2380-16", .driver_data = (kernel_ulong_t)<c2380_16_chip_info },
+ { }
+};
+MODULE_DEVICE_TABLE(spi, ltc2378_spi_id);
+
+static struct spi_driver ltc2378_driver = {
+ .driver = {
+ .name = "ltc2378",
+ .of_match_table = ltc2378_of_match
+ },
+ .probe = ltc2378_probe,
+ .id_table = ltc2378_spi_id,
+};
+module_spi_driver(ltc2378_driver);
+
+MODULE_AUTHOR("Marcelo Schmitt <marcelo.schmitt@analog.com>");
+MODULE_DESCRIPTION("Analog Devices LTC2378 ADC series driver");
+MODULE_LICENSE("GPL");
--
2.53.0
^ permalink raw reply related [flat|nested] 10+ messages in thread* Re: [PATCH v9 2/6] iio: adc: ltc2378: Add support for LTC2378-20 and similar ADCs
2026-07-27 21:30 ` [PATCH v9 2/6] iio: adc: ltc2378: Add support for LTC2378-20 and similar ADCs Marcelo Schmitt
@ 2026-07-27 21:42 ` sashiko-bot
0 siblings, 0 replies; 10+ messages in thread
From: sashiko-bot @ 2026-07-27 21:42 UTC (permalink / raw)
To: Marcelo Schmitt; +Cc: conor+dt, robh, devicetree
Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Holding CNV high during SPI transfer breaks 3-wire SPI wiring mode.
--
--- Patch [2]: [PATCH v9 2/6] iio: adc: ltc2378: Add support for LTC2378-20 and similar ADCs ---
commit 4d4231cee28f9742280dd61ed84f85cf3b4e0386
Author: Marcelo Schmitt <marcelo.schmitt@analog.com>
iio: adc: ltc2378: Add support for LTC2378-20 and similar ADCs
This commit adds support for the Analog Devices LTC2378-20 and similar
analog-to-digital converters.
> diff --git a/drivers/iio/adc/ltc2378.c b/drivers/iio/adc/ltc2378.c
> new file mode 100644
> --- /dev/null
> +++ b/drivers/iio/adc/ltc2378.c
[ ... ]
> +static int ltc2378_convert_and_acquire(struct ltc2378_state *st)
> +{
> + int ret;
> +
> + /* Cause a rising edge of CNV to initiate a new ADC conversion */
> + gpiod_set_value_cansleep(st->cnv_gpio, 1);
> + fsleep(LTC2378_MAX_DATA_WAIT_US);
> + ret = spi_sync_transfer(st->spi, &st->xfer, 1);
[Severity: High]
Does holding CNV high during the SPI transfer break 3-wire SPI wiring mode?
In 3-wire mode (where SDI is tied to GND), the SDO pin of the ADC remains in
a high-impedance state as long as the CNV pin is held high.
Since the CNV pin remains high throughout the SPI transfer, could the SPI
controller clock in garbage data from a floating bus?
Would lowering CNV after the fsleep() wait and before calling
spi_sync_transfer() correctly enable SDO for 3-wire mode while remaining
compatible with 4-wire (CS) mode?
> + gpiod_set_value_cansleep(st->cnv_gpio, 0);
> +
> + return ret;
> +}
[ ... ]
--
Sashiko AI review · https://sashiko.dev/#/patchset/cover.1785186980.git.marcelo.schmitt@analog.com?part=2
^ permalink raw reply [flat|nested] 10+ messages in thread
* [PATCH v9 3/6] iio: adc: ltc2378: Enable high-speed data capture
2026-07-27 21:30 [PATCH v9 0/6] iio: adc: Add support for LTC2378 and similar ADCs Marcelo Schmitt
2026-07-27 21:30 ` [PATCH v9 1/6] dt-bindings: iio: adc: Add ltc2378 Marcelo Schmitt
2026-07-27 21:30 ` [PATCH v9 2/6] iio: adc: ltc2378: Add support for LTC2378-20 and similar ADCs Marcelo Schmitt
@ 2026-07-27 21:31 ` Marcelo Schmitt
2026-07-27 21:49 ` sashiko-bot
2026-07-27 21:31 ` [PATCH v9 4/6] iio: adc: ltc2378: Enable triggered buffer " Marcelo Schmitt
` (2 subsequent siblings)
5 siblings, 1 reply; 10+ messages in thread
From: Marcelo Schmitt @ 2026-07-27 21:31 UTC (permalink / raw)
To: linux-iio, devicetree, linux-kernel
Cc: jic23, nuno.sa, Michael.Hennerich, dlechner, andy, robh, krzk+dt,
conor+dt, julianbraha, marcelo.schmitt1, Andy Shevchenko
Make use of SPI transfer offloading to speed up data capture, enabling data
acquisition at faster sample rates (up to 2 MSPS).
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Reviewed-by: David Lechner <dlechner@baylibre.com>
Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
---
Change log v8 -> v9:
No changes in v9.
drivers/iio/adc/Kconfig | 6 +
drivers/iio/adc/ltc2378.c | 404 +++++++++++++++++++++++++++++++++++++-
2 files changed, 407 insertions(+), 3 deletions(-)
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 220c6739a8f2..96df8453b826 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -948,6 +948,12 @@ config LTC2378
depends on SPI
depends on REGULATOR || COMPILE_TEST
depends on GPIOLIB
+ depends on PWM
+ select IIO_BUFFER
+ select IIO_BUFFER_DMA
+ select IIO_BUFFER_DMAENGINE
+ select SPI_OFFLOAD
+ select SPI_OFFLOAD_TRIGGER_PWM
help
Say yes here to build support for Analog Devices LTC2378-20 and
similar analog to digital converters.
diff --git a/drivers/iio/adc/ltc2378.c b/drivers/iio/adc/ltc2378.c
index d161435fc3a3..48380a2d7dc6 100644
--- a/drivers/iio/adc/ltc2378.c
+++ b/drivers/iio/adc/ltc2378.c
@@ -16,16 +16,27 @@
#include <linux/device-id/of.h>
#include <linux/err.h>
#include <linux/gpio/consumer.h>
+#include <linux/math64.h>
+#include <linux/minmax.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/regulator/consumer.h>
+#include <linux/pwm.h>
#include <linux/spi/spi.h>
+#include <linux/spi/offload/consumer.h>
+#include <linux/spi/offload/types.h>
+#include <linux/time64.h>
#include <linux/types.h>
#include <linux/units.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/buffer-dmaengine.h>
#include <linux/iio/iio.h>
#include <linux/iio/types.h>
+#define LTC2378_TDSDOBUSYL_NS 5
+#define LTC2378_TBUSYLH_NS 13
+#define LTC2378_TCNV_HIGH_NS 20
#define LTC2378_MAX_DATA_WAIT_US 4 /* max(TBUSYLH + TCONV + TDSDOBUSYL) */
#define LTC2378_CHANNEL(_sign, _real_bits, _storage_bits) \
@@ -54,9 +65,49 @@
#define LTC2378_PSEUDO_DIFF_CHANNEL(_real_bits) \
LTC2378_CHANNEL(0, _real_bits, (((_real_bits) > 16) ? 32 : 16))
+#define LTC2378_OFFLOAD_CHANNEL(_sign, _real_bits, _storage_bits) \
+{ \
+ .type = IIO_VOLTAGE, \
+ .indexed = 1, \
+ .differential = _sign, \
+ .channel = 0, \
+ .channel2 = _sign ? 1 : 0, \
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | \
+ BIT(IIO_CHAN_INFO_SCALE) | \
+ BIT(IIO_CHAN_INFO_SAMP_FREQ), \
+ .info_mask_separate_available = BIT(IIO_CHAN_INFO_SAMP_FREQ), \
+ .scan_index = 0, \
+ .scan_type = { \
+ .format = _sign ? IIO_SCAN_FORMAT_SIGNED_INT : \
+ IIO_SCAN_FORMAT_UNSIGNED_INT, \
+ .realbits = _real_bits, \
+ .storagebits = _storage_bits, \
+ .shift = 0, \
+ .endianness = IIO_CPU, \
+ }, \
+}
+
+/*
+ * Currently, the available offload hardware + DMA configuration only supports
+ * pushing 32-bit data elements to DMA IIO buffers in CPU endianness. For 16-bit
+ * precision parts, those 32-bit elements (in CPU endianness) contain 2 bytes
+ * with data and 2 bytes always zeroed out. Nevertheless, for the offload use
+ * case, the IIO buffer is configured for 32 storage bits in CPU endianness so
+ * data is correctly aligned in user space despite 2 out of the 4 bytes being
+ * zeros.
+ */
+#define LTC2378_OFFLOAD_DIFF_CHANNEL(_real_bits) \
+ LTC2378_OFFLOAD_CHANNEL(1, (_real_bits), 32)
+
+#define LTC2378_OFFLOAD_PSEUDO_DIFF_CHANNEL(_real_bits) \
+ LTC2378_OFFLOAD_CHANNEL(0, (_real_bits), 32)
+
struct ltc2378_chip_info {
const char *name;
struct iio_chan_spec chan;
+ struct iio_chan_spec offload_chan;
+ unsigned int max_sample_rate_Hz;
+ unsigned int tconv_ns;
};
struct ltc2378_state {
@@ -66,6 +117,15 @@ struct ltc2378_state {
struct mutex lock; /* Protect data acquisition cycle */
int ref_uV;
struct spi_transfer xfer;
+ struct spi_transfer offload_xfer;
+ struct spi_offload *offload;
+ struct spi_offload_trigger *offload_trigger;
+ struct pwm_waveform cnv_wf;
+ struct spi_message offload_msg;
+ struct spi_offload_trigger_config offload_trigger_config;
+ struct pwm_device *cnv_trigger;
+ unsigned int cnv_Hz;
+ unsigned int sample_freq_range[3];
/*
* DMA (thus cache coherency maintenance) requires the transfer buffers
@@ -85,96 +145,153 @@ struct ltc2378_state {
static const struct ltc2378_chip_info ltc2364_16_chip_info = {
.name = "ltc2364-16",
.chan = LTC2378_PSEUDO_DIFF_CHANNEL(16),
+ .offload_chan = LTC2378_OFFLOAD_PSEUDO_DIFF_CHANNEL(16),
+ .max_sample_rate_Hz = 250 * HZ_PER_KHZ,
+ .tconv_ns = 3000,
};
static const struct ltc2378_chip_info ltc2364_18_chip_info = {
.name = "ltc2364-18",
.chan = LTC2378_PSEUDO_DIFF_CHANNEL(18),
+ .offload_chan = LTC2378_OFFLOAD_PSEUDO_DIFF_CHANNEL(18),
+ .max_sample_rate_Hz = 250 * HZ_PER_KHZ,
+ .tconv_ns = 3000,
};
static const struct ltc2378_chip_info ltc2367_16_chip_info = {
.name = "ltc2367-16",
.chan = LTC2378_PSEUDO_DIFF_CHANNEL(16),
+ .offload_chan = LTC2378_OFFLOAD_PSEUDO_DIFF_CHANNEL(16),
+ .max_sample_rate_Hz = 500 * HZ_PER_KHZ,
+ .tconv_ns = 1500,
};
static const struct ltc2378_chip_info ltc2367_18_chip_info = {
.name = "ltc2367-18",
.chan = LTC2378_PSEUDO_DIFF_CHANNEL(18),
+ .offload_chan = LTC2378_OFFLOAD_PSEUDO_DIFF_CHANNEL(18),
+ .max_sample_rate_Hz = 500 * HZ_PER_KHZ,
+ .tconv_ns = 1500,
};
static const struct ltc2378_chip_info ltc2368_16_chip_info = {
.name = "ltc2368-16",
.chan = LTC2378_PSEUDO_DIFF_CHANNEL(16),
+ .offload_chan = LTC2378_OFFLOAD_PSEUDO_DIFF_CHANNEL(16),
+ .max_sample_rate_Hz = 1 * HZ_PER_MHZ,
+ .tconv_ns = 527,
};
static const struct ltc2378_chip_info ltc2368_18_chip_info = {
.name = "ltc2368-18",
.chan = LTC2378_PSEUDO_DIFF_CHANNEL(18),
+ .offload_chan = LTC2378_OFFLOAD_PSEUDO_DIFF_CHANNEL(18),
+ .max_sample_rate_Hz = 1 * HZ_PER_MHZ,
+ .tconv_ns = 527,
};
static const struct ltc2378_chip_info ltc2369_18_chip_info = {
.name = "ltc2369-18",
.chan = LTC2378_PSEUDO_DIFF_CHANNEL(18),
+ .offload_chan = LTC2378_OFFLOAD_PSEUDO_DIFF_CHANNEL(18),
+ .max_sample_rate_Hz = 1600 * HZ_PER_KHZ,
+ .tconv_ns = 412,
};
static const struct ltc2378_chip_info ltc2370_16_chip_info = {
.name = "ltc2370-16",
.chan = LTC2378_PSEUDO_DIFF_CHANNEL(16),
+ .offload_chan = LTC2378_OFFLOAD_PSEUDO_DIFF_CHANNEL(16),
+ .max_sample_rate_Hz = 2 * HZ_PER_MHZ,
+ .tconv_ns = 322,
};
static const struct ltc2378_chip_info ltc2376_16_chip_info = {
.name = "ltc2376-16",
.chan = LTC2378_DIFF_CHANNEL(16),
+ .offload_chan = LTC2378_OFFLOAD_DIFF_CHANNEL(16),
+ .max_sample_rate_Hz = 250 * HZ_PER_KHZ,
+ .tconv_ns = 3000,
};
static const struct ltc2378_chip_info ltc2376_18_chip_info = {
.name = "ltc2376-18",
.chan = LTC2378_DIFF_CHANNEL(18),
+ .offload_chan = LTC2378_OFFLOAD_DIFF_CHANNEL(18),
+ .max_sample_rate_Hz = 250 * HZ_PER_KHZ,
+ .tconv_ns = 3000,
};
static const struct ltc2378_chip_info ltc2376_20_chip_info = {
.name = "ltc2376-20",
.chan = LTC2378_DIFF_CHANNEL(20),
+ .offload_chan = LTC2378_OFFLOAD_DIFF_CHANNEL(20),
+ .max_sample_rate_Hz = 250 * HZ_PER_KHZ,
+ .tconv_ns = 3000,
};
static const struct ltc2378_chip_info ltc2377_16_chip_info = {
.name = "ltc2377-16",
.chan = LTC2378_DIFF_CHANNEL(16),
+ .offload_chan = LTC2378_OFFLOAD_DIFF_CHANNEL(16),
+ .max_sample_rate_Hz = 500 * HZ_PER_KHZ,
+ .tconv_ns = 1500,
};
static const struct ltc2378_chip_info ltc2377_18_chip_info = {
.name = "ltc2377-18",
.chan = LTC2378_DIFF_CHANNEL(18),
+ .offload_chan = LTC2378_OFFLOAD_DIFF_CHANNEL(18),
+ .max_sample_rate_Hz = 500 * HZ_PER_KHZ,
+ .tconv_ns = 1500,
};
static const struct ltc2378_chip_info ltc2377_20_chip_info = {
.name = "ltc2377-20",
.chan = LTC2378_DIFF_CHANNEL(20),
+ .offload_chan = LTC2378_OFFLOAD_DIFF_CHANNEL(20),
+ .max_sample_rate_Hz = 500 * HZ_PER_KHZ,
+ .tconv_ns = 1500,
};
static const struct ltc2378_chip_info ltc2378_16_chip_info = {
.name = "ltc2378-16",
.chan = LTC2378_DIFF_CHANNEL(16),
+ .offload_chan = LTC2378_OFFLOAD_DIFF_CHANNEL(16),
+ .max_sample_rate_Hz = 1 * HZ_PER_MHZ,
+ .tconv_ns = 527,
};
static const struct ltc2378_chip_info ltc2378_18_chip_info = {
.name = "ltc2378-18",
.chan = LTC2378_DIFF_CHANNEL(18),
+ .offload_chan = LTC2378_OFFLOAD_DIFF_CHANNEL(18),
+ .max_sample_rate_Hz = 1 * HZ_PER_MHZ,
+ .tconv_ns = 527,
};
static const struct ltc2378_chip_info ltc2378_20_chip_info = {
.name = "ltc2378-20",
.chan = LTC2378_DIFF_CHANNEL(20),
+ .offload_chan = LTC2378_OFFLOAD_DIFF_CHANNEL(20),
+ .max_sample_rate_Hz = 1 * HZ_PER_MHZ,
+ .tconv_ns = 675,
};
static const struct ltc2378_chip_info ltc2379_18_chip_info = {
.name = "ltc2379-18",
.chan = LTC2378_DIFF_CHANNEL(18),
+ .offload_chan = LTC2378_OFFLOAD_DIFF_CHANNEL(18),
+ .max_sample_rate_Hz = 1600 * HZ_PER_KHZ,
+ .tconv_ns = 412,
};
static const struct ltc2378_chip_info ltc2380_16_chip_info = {
.name = "ltc2380-16",
.chan = LTC2378_DIFF_CHANNEL(16),
+ .offload_chan = LTC2378_OFFLOAD_DIFF_CHANNEL(16),
+ .max_sample_rate_Hz = 2 * HZ_PER_MHZ,
+ .tconv_ns = 322,
};
static int ltc2378_convert_and_acquire(struct ltc2378_state *st)
@@ -257,7 +374,137 @@ 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;
+ default:
+ return -EINVAL;
+ }
+}
+static int ltc2378_read_avail(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ const int **vals, int *type, int *length, long mask)
+{
+ struct ltc2378_state *st = iio_priv(indio_dev);
+
+ switch (mask) {
+ case IIO_CHAN_INFO_SAMP_FREQ:
+ *vals = st->sample_freq_range;
+ *type = IIO_VAL_INT;
+ return IIO_AVAIL_RANGE;
+ default:
+ return -EINVAL;
+ }
+}
+
+/*
+ * SPI offload wiring schema
+ *
+ * +-------------+ +-------------+
+ * | CNV |<-----+--| GPIO |
+ * | | +--| PWM0 |
+ * | | | |
+ * | | +--| PWM1 |
+ * | | | +-------------+
+ * | | +->| TRIGGER |
+ * | | | |
+ * | ADC | | SPI |
+ * | | | controller |
+ * | | | |
+ * | SDI |<--------| SDO |
+ * | SDO |-------->| SDI |
+ * | SCLK |<--------| SCLK |
+ * +-------------+ +-------------+
+ *
+ */
+static int ltc2378_update_conversion_rate(struct ltc2378_state *st, int freq_Hz)
+{
+ struct spi_offload_trigger_config config = st->offload_trigger_config;
+ unsigned int min_read_offset, offload_period_ns;
+ struct pwm_waveform cnv_wf = { };
+ u64 target = LTC2378_TCNV_HIGH_NS;
+ unsigned int count;
+ u64 offload_offset_ns;
+ int ret;
+
+ if (freq_Hz == 0)
+ return -EINVAL;
+
+ if (!in_range(freq_Hz, 1, st->info->max_sample_rate_Hz))
+ return -ERANGE;
+
+ /* Configure CNV PWM waveform */
+ cnv_wf.period_length_ns = DIV_ROUND_CLOSEST(NSEC_PER_SEC, freq_Hz);
+
+ /*
+ * Ensure CNV high time meets minimum requirement (20ns). The PWM
+ * hardware may round the duty cycle, so iterate until we get at least
+ * the minimum required high time (or reach a try count limit).
+ */
+ count = 100;
+ do {
+ cnv_wf.duty_length_ns = target;
+ ret = pwm_round_waveform_might_sleep(st->cnv_trigger, &cnv_wf);
+ if (ret)
+ return ret;
+ target += 10; /* Increment by PWM duty cycle period */
+ } while (count-- && cnv_wf.duty_length_ns < LTC2378_TCNV_HIGH_NS);
+
+ /* Check the minimum CNV high time is met */
+ if (cnv_wf.duty_length_ns < LTC2378_TCNV_HIGH_NS)
+ return -EDOM;
+
+ /*
+ * Configure SPI offload PWM trigger.
+ * The trigger should fire after tBUSYLH + tCONV + tDSDOBUSYL.
+ * Minimum time needed: TBUSYLH (13ns) + TCONV (part-specific) + TDSDOBUSYL (5ns)
+ *
+ * Use the same period as CNV PWM to avoid timing issues.
+ * Convert back from period to frequency for the SPI offload API.
+ */
+ offload_period_ns = cnv_wf.period_length_ns;
+ config.periodic.frequency_hz = div_u64(HZ_PER_GHZ, offload_period_ns);
+ min_read_offset = LTC2378_TBUSYLH_NS + st->info->tconv_ns + LTC2378_TDSDOBUSYL_NS;
+ offload_offset_ns = min_read_offset;
+ count = 100;
+ do {
+ config.periodic.offset_ns = offload_offset_ns;
+ ret = spi_offload_trigger_validate(st->offload_trigger, &config);
+ if (ret)
+ return ret;
+ offload_offset_ns += 10;
+ } while (count-- && config.periodic.offset_ns < min_read_offset);
+
+ /* Check the minimum CNV to SCLK delay is met */
+ if (config.periodic.offset_ns < min_read_offset)
+ return -EDOM;
+
+ /* Check the PWM periods remain the same */
+ offload_period_ns = div64_u64(HZ_PER_GHZ, config.periodic.frequency_hz);
+ if (cnv_wf.period_length_ns != offload_period_ns)
+ return -EDOM;
+
+ st->offload_trigger_config = config;
+ st->cnv_wf = cnv_wf;
+ st->cnv_Hz = DIV_ROUND_CLOSEST_ULL(HZ_PER_GHZ, cnv_wf.period_length_ns);
+
+ return 0;
+}
+
+static int ltc2378_write_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int val, int val2, long mask)
+{
+ struct ltc2378_state *st = iio_priv(indio_dev);
+
+ IIO_DEV_ACQUIRE_DIRECT_MODE(indio_dev, claim);
+ if (IIO_DEV_ACQUIRE_FAILED(claim))
+ return -EBUSY;
+
+ switch (mask) {
+ case IIO_CHAN_INFO_SAMP_FREQ:
+ return ltc2378_update_conversion_rate(st, val);
default:
return -EINVAL;
}
@@ -267,6 +514,111 @@ static const struct iio_info ltc2378_iio_info = {
.read_raw = <c2378_read_raw,
};
+static const struct iio_info ltc2378_offload_iio_info = {
+ .read_raw = <c2378_read_raw,
+ .read_avail = <c2378_read_avail,
+ .write_raw = <c2378_write_raw,
+};
+
+static int ltc2378_offload_buffer_postenable(struct iio_dev *indio_dev)
+{
+ struct ltc2378_state *st = iio_priv(indio_dev);
+ int ret;
+
+ ret = pwm_set_waveform_might_sleep(st->cnv_trigger, &st->cnv_wf, true);
+ if (ret)
+ return ret;
+
+ ret = spi_offload_trigger_enable(st->offload, st->offload_trigger,
+ &st->offload_trigger_config);
+ if (ret)
+ goto out_pwm_disable;
+
+ return 0;
+
+out_pwm_disable:
+ pwm_disable(st->cnv_trigger);
+ return ret;
+}
+
+static int ltc2378_offload_buffer_predisable(struct iio_dev *indio_dev)
+{
+ struct ltc2378_state *st = iio_priv(indio_dev);
+
+ spi_offload_trigger_disable(st->offload, st->offload_trigger);
+ pwm_disable(st->cnv_trigger);
+
+ return 0;
+}
+
+static const struct iio_buffer_setup_ops ltc2378_offload_buffer_ops = {
+ .postenable = <c2378_offload_buffer_postenable,
+ .predisable = <c2378_offload_buffer_predisable,
+};
+
+static int ltc2378_prepare_offload_message(struct device *dev,
+ struct ltc2378_state *st)
+{
+ unsigned int resolution = st->info->offload_chan.scan_type.realbits;
+
+ st->offload_xfer.bits_per_word = resolution;
+ st->offload_xfer.len = spi_bpw_to_bytes(resolution);
+ st->offload_xfer.offload_flags = SPI_OFFLOAD_XFER_RX_STREAM;
+
+ /* Initialize message with offload */
+ spi_message_init_with_transfers(&st->offload_msg, &st->offload_xfer, 1);
+ st->offload_msg.offload = st->offload;
+
+ return devm_spi_optimize_message(dev, st->spi, &st->offload_msg);
+}
+
+static int ltc2378_spi_offload_setup(struct iio_dev *indio_dev,
+ struct ltc2378_state *st)
+{
+ struct device *dev = &st->spi->dev;
+ struct dma_chan *rx_dma;
+
+ indio_dev->setup_ops = <c2378_offload_buffer_ops;
+
+ st->offload_trigger = devm_spi_offload_trigger_get(dev, st->offload,
+ SPI_OFFLOAD_TRIGGER_PERIODIC);
+ if (IS_ERR(st->offload_trigger))
+ return dev_err_probe(dev, PTR_ERR(st->offload_trigger),
+ "failed to get offload trigger\n");
+
+ st->offload_trigger_config.type = SPI_OFFLOAD_TRIGGER_PERIODIC;
+
+ rx_dma = devm_spi_offload_rx_stream_request_dma_chan(dev, st->offload);
+ if (IS_ERR(rx_dma))
+ return dev_err_probe(dev, PTR_ERR(rx_dma), "failed to get offload RX DMA\n");
+
+ return devm_iio_dmaengine_buffer_setup_with_handle(dev, indio_dev, rx_dma,
+ IIO_BUFFER_DIRECTION_IN);
+}
+
+static int ltc2378_pwm_get(struct ltc2378_state *st)
+{
+ struct device *dev = &st->spi->dev;
+
+ st->cnv_trigger = devm_pwm_get(dev, NULL);
+ if (IS_ERR(st->cnv_trigger))
+ return dev_err_probe(dev, PTR_ERR(st->cnv_trigger),
+ "failed to get cnv pwm\n");
+
+ /*
+ * Disable the PWM connected to CNV in case it was left running by
+ * something else.
+ */
+ pwm_disable(st->cnv_trigger);
+
+ return 0;
+}
+
+static const struct spi_offload_config ltc2378_offload_config = {
+ .capability_flags = SPI_OFFLOAD_CAP_TRIGGER |
+ SPI_OFFLOAD_CAP_RX_STREAM_DMA,
+};
+
static int ltc2378_ref_setup(struct device *dev, struct ltc2378_state *st)
{
int ret;
@@ -307,7 +659,6 @@ static int ltc2378_probe(struct spi_device *spi)
return ret;
indio_dev->name = st->info->name;
- indio_dev->info = <c2378_iio_info;
indio_dev->modes = INDIO_DIRECT_MODE;
st->cnv_gpio = devm_gpiod_get(dev, "cnv", GPIOD_OUT_LOW);
@@ -315,8 +666,53 @@ static int ltc2378_probe(struct spi_device *spi)
return dev_err_probe(dev, PTR_ERR(st->cnv_gpio),
"failed to get CNV GPIO");
- indio_dev->channels = &st->info->chan;
- indio_dev->num_channels = 1;
+ st->offload = devm_spi_offload_get(dev, spi, <c2378_offload_config);
+ ret = PTR_ERR_OR_ZERO(st->offload);
+ /* Fall back to low speed usage when no SPI offload is available. */
+ if (ret == -ENODEV) {
+ indio_dev->info = <c2378_iio_info;
+ indio_dev->channels = &st->info->chan;
+ indio_dev->num_channels = 1;
+ } else if (ret) {
+ return dev_err_probe(dev, ret, "failed to get offload\n");
+ } else {
+ indio_dev->info = <c2378_offload_iio_info;
+ indio_dev->channels = &st->info->offload_chan;
+ indio_dev->num_channels = 1;
+ ret = ltc2378_spi_offload_setup(indio_dev, st);
+ if (ret)
+ return dev_err_probe(dev, ret,
+ "failed to setup SPI offload\n");
+
+ ret = ltc2378_pwm_get(st);
+ if (ret)
+ return dev_err_probe(dev, ret, "failed to get PWM\n");
+
+ st->sample_freq_range[0] = 1; /* min */
+ st->sample_freq_range[1] = 1; /* step */
+ st->sample_freq_range[2] = st->info->max_sample_rate_Hz; /* max */
+
+ /*
+ * Start with a slower sampling rate so there is some room for
+ * adjusting the sample averaging and the sampling frequency
+ * without hitting the maximum conversion rate.
+ */
+ ret = ltc2378_update_conversion_rate(st, st->info->max_sample_rate_Hz >> 4);
+ if (ret)
+ return dev_err_probe(dev, ret,
+ "failed to set offload samp freq\n");
+
+ ret = ltc2378_prepare_offload_message(&spi->dev, st);
+ if (ret)
+ return dev_err_probe(dev, ret, "failed to optimize SPI message\n");
+
+ /*
+ * Set single-read transfer bits_per_word so the SPI subsystem
+ * rearranges data to CPU endianness, enabling us to reuse
+ * offload_chan specifications for single-shot reads.
+ */
+ st->xfer.bits_per_word = st->info->offload_chan.scan_type.realbits;
+ }
st->xfer.rx_buf = &st->scan.data;
st->xfer.len = spi_bpw_to_bytes(indio_dev->channels[0].scan_type.realbits);
@@ -385,3 +781,5 @@ module_spi_driver(ltc2378_driver);
MODULE_AUTHOR("Marcelo Schmitt <marcelo.schmitt@analog.com>");
MODULE_DESCRIPTION("Analog Devices LTC2378 ADC series driver");
MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS("IIO_DMAENGINE_BUFFER");
+MODULE_IMPORT_NS("SPI_OFFLOAD");
--
2.53.0
^ permalink raw reply related [flat|nested] 10+ messages in thread* Re: [PATCH v9 3/6] iio: adc: ltc2378: Enable high-speed data capture
2026-07-27 21:31 ` [PATCH v9 3/6] iio: adc: ltc2378: Enable high-speed data capture Marcelo Schmitt
@ 2026-07-27 21:49 ` sashiko-bot
0 siblings, 0 replies; 10+ messages in thread
From: sashiko-bot @ 2026-07-27 21:49 UTC (permalink / raw)
To: Marcelo Schmitt; +Cc: robh, conor+dt, devicetree
Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Missing bounds check on rounded PWM period leads to divide-by-zero panic and ADC overclocking.
--
--- Patch [3]: [PATCH v9 3/6] iio: adc: ltc2378: Enable high-speed data capture ---
commit ebabc81c7c955467e478de14bdd64baea8b0e439
Author: Marcelo Schmitt <marcelo.schmitt@analog.com>
iio: adc: ltc2378: Enable high-speed data capture
Make use of SPI transfer offloading to speed up data capture, enabling data
acquisition at faster sample rates (up to 2 MSPS).
> diff --git a/drivers/iio/adc/ltc2378.c b/drivers/iio/adc/ltc2378.c
> index d161435fc3a31..48380a2d7dc66 100644
> --- a/drivers/iio/adc/ltc2378.c
> +++ b/drivers/iio/adc/ltc2378.c
[ ... ]
> +static int ltc2378_update_conversion_rate(struct ltc2378_state *st, int freq_Hz)
> +{
> + struct spi_offload_trigger_config config = st->offload_trigger_config;
> + unsigned int min_read_offset, offload_period_ns;
> + struct pwm_waveform cnv_wf = { };
> + u64 target = LTC2378_TCNV_HIGH_NS;
> + unsigned int count;
> + u64 offload_offset_ns;
> + int ret;
> +
> + if (freq_Hz == 0)
> + return -EINVAL;
> +
> + if (!in_range(freq_Hz, 1, st->info->max_sample_rate_Hz))
> + return -ERANGE;
> +
> + /* Configure CNV PWM waveform */
> + cnv_wf.period_length_ns = DIV_ROUND_CLOSEST(NSEC_PER_SEC, freq_Hz);
> +
> + /*
> + * Ensure CNV high time meets minimum requirement (20ns). The PWM
> + * hardware may round the duty cycle, so iterate until we get at least
> + * the minimum required high time (or reach a try count limit).
> + */
> + count = 100;
> + do {
> + cnv_wf.duty_length_ns = target;
> + ret = pwm_round_waveform_might_sleep(st->cnv_trigger, &cnv_wf);
> + if (ret)
> + return ret;
> + target += 10; /* Increment by PWM duty cycle period */
> + } while (count-- && cnv_wf.duty_length_ns < LTC2378_TCNV_HIGH_NS);
> +
> + /* Check the minimum CNV high time is met */
> + if (cnv_wf.duty_length_ns < LTC2378_TCNV_HIGH_NS)
> + return -EDOM;
> +
> + /*
> + * Configure SPI offload PWM trigger.
> + * The trigger should fire after tBUSYLH + tCONV + tDSDOBUSYL.
> + * Minimum time needed: TBUSYLH (13ns) + TCONV (part-specific) + TDSDOBUSYL (5ns)
> + *
> + * Use the same period as CNV PWM to avoid timing issues.
> + * Convert back from period to frequency for the SPI offload API.
> + */
> + offload_period_ns = cnv_wf.period_length_ns;
> + config.periodic.frequency_hz = div_u64(HZ_PER_GHZ, offload_period_ns);
[Severity: High]
If the hardware PWM driver rounds the requested period up beyond 1e9 ns
(for example, if a 1 Hz frequency request yields 1,000,000,001 ns), does
this division evaluate to 0?
> + min_read_offset = LTC2378_TBUSYLH_NS + st->info->tconv_ns + LTC2378_TDSDOBUSYL_NS;
> + offload_offset_ns = min_read_offset;
> + count = 100;
> + do {
> + config.periodic.offset_ns = offload_offset_ns;
> + ret = spi_offload_trigger_validate(st->offload_trigger, &config);
> + if (ret)
> + return ret;
> + offload_offset_ns += 10;
> + } while (count-- && config.periodic.offset_ns < min_read_offset);
> +
> + /* Check the minimum CNV to SCLK delay is met */
> + if (config.periodic.offset_ns < min_read_offset)
> + return -EDOM;
> +
> + /* Check the PWM periods remain the same */
> + offload_period_ns = div64_u64(HZ_PER_GHZ, config.periodic.frequency_hz);
[Severity: High]
If frequency_hz evaluates to 0 above, does this cause a divide-by-zero
panic here?
Additionally, if the PWM driver rounds the period down when the user
requests max_sample_rate_Hz, could the actual frequency silently exceed
the ADC's hardware limits? Does the period need to be re-validated against
bounds after pwm_round_waveform_might_sleep() is called?
> + if (cnv_wf.period_length_ns != offload_period_ns)
> + return -EDOM;
> +
> + st->offload_trigger_config = config;
> + st->cnv_wf = cnv_wf;
> + st->cnv_Hz = DIV_ROUND_CLOSEST_ULL(HZ_PER_GHZ, cnv_wf.period_length_ns);
> +
> + return 0;
> +}
--
Sashiko AI review · https://sashiko.dev/#/patchset/cover.1785186980.git.marcelo.schmitt@analog.com?part=3
^ permalink raw reply [flat|nested] 10+ messages in thread
* [PATCH v9 4/6] iio: adc: ltc2378: Enable triggered buffer data capture
2026-07-27 21:30 [PATCH v9 0/6] iio: adc: Add support for LTC2378 and similar ADCs Marcelo Schmitt
` (2 preceding siblings ...)
2026-07-27 21:31 ` [PATCH v9 3/6] iio: adc: ltc2378: Enable high-speed data capture Marcelo Schmitt
@ 2026-07-27 21:31 ` Marcelo Schmitt
2026-07-27 21:31 ` [PATCH v9 5/6] iio: adc: ltc2378: Add support for LTC2338-18 Marcelo Schmitt
2026-07-27 21:32 ` [PATCH v9 6/6] iio: ABI: Encourage differential voltage ABI usage Marcelo Schmitt
5 siblings, 0 replies; 10+ messages in thread
From: Marcelo Schmitt @ 2026-07-27 21:31 UTC (permalink / raw)
To: linux-iio, devicetree, linux-kernel
Cc: jic23, nuno.sa, Michael.Hennerich, dlechner, andy, robh, krzk+dt,
conor+dt, julianbraha, marcelo.schmitt1, Andy Shevchenko
Enable users to run triggered data captures with LTC2378 and similar ADCs.
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Reviewed-by: David Lechner <dlechner@baylibre.com>
Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
---
Change log v8 -> v9:
No changes in v9.
drivers/iio/adc/Kconfig | 1 +
drivers/iio/adc/ltc2378.c | 73 +++++++++++++++++++++++++++------------
2 files changed, 52 insertions(+), 22 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 48380a2d7dc6..146eaadbeb6c 100644
--- a/drivers/iio/adc/ltc2378.c
+++ b/drivers/iio/adc/ltc2378.c
@@ -6,6 +6,7 @@
* Author: Marcelo Schmitt <marcelo.schmitt@analog.com>
*/
+#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
@@ -104,7 +107,7 @@
struct ltc2378_chip_info {
const char *name;
- 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;
@@ -144,7 +147,7 @@ struct ltc2378_state {
static const struct ltc2378_chip_info ltc2364_16_chip_info = {
.name = "ltc2364-16",
- .chan = LTC2378_PSEUDO_DIFF_CHANNEL(16),
+ .chan = { LTC2378_PSEUDO_DIFF_CHANNEL(16), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_PSEUDO_DIFF_CHANNEL(16),
.max_sample_rate_Hz = 250 * HZ_PER_KHZ,
.tconv_ns = 3000,
@@ -152,7 +155,7 @@ 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_PSEUDO_DIFF_CHANNEL(18),
+ .chan = { LTC2378_PSEUDO_DIFF_CHANNEL(18), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_PSEUDO_DIFF_CHANNEL(18),
.max_sample_rate_Hz = 250 * HZ_PER_KHZ,
.tconv_ns = 3000,
@@ -160,7 +163,7 @@ 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_PSEUDO_DIFF_CHANNEL(16),
+ .chan = { LTC2378_PSEUDO_DIFF_CHANNEL(16), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_PSEUDO_DIFF_CHANNEL(16),
.max_sample_rate_Hz = 500 * HZ_PER_KHZ,
.tconv_ns = 1500,
@@ -168,7 +171,7 @@ 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_PSEUDO_DIFF_CHANNEL(18),
+ .chan = { LTC2378_PSEUDO_DIFF_CHANNEL(18), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_PSEUDO_DIFF_CHANNEL(18),
.max_sample_rate_Hz = 500 * HZ_PER_KHZ,
.tconv_ns = 1500,
@@ -176,7 +179,7 @@ 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_PSEUDO_DIFF_CHANNEL(16),
+ .chan = { LTC2378_PSEUDO_DIFF_CHANNEL(16), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_PSEUDO_DIFF_CHANNEL(16),
.max_sample_rate_Hz = 1 * HZ_PER_MHZ,
.tconv_ns = 527,
@@ -184,7 +187,7 @@ 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_PSEUDO_DIFF_CHANNEL(18),
+ .chan = { LTC2378_PSEUDO_DIFF_CHANNEL(18), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_PSEUDO_DIFF_CHANNEL(18),
.max_sample_rate_Hz = 1 * HZ_PER_MHZ,
.tconv_ns = 527,
@@ -192,7 +195,7 @@ 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_PSEUDO_DIFF_CHANNEL(18),
+ .chan = { LTC2378_PSEUDO_DIFF_CHANNEL(18), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_PSEUDO_DIFF_CHANNEL(18),
.max_sample_rate_Hz = 1600 * HZ_PER_KHZ,
.tconv_ns = 412,
@@ -200,7 +203,7 @@ 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_PSEUDO_DIFF_CHANNEL(16),
+ .chan = { LTC2378_PSEUDO_DIFF_CHANNEL(16), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_PSEUDO_DIFF_CHANNEL(16),
.max_sample_rate_Hz = 2 * HZ_PER_MHZ,
.tconv_ns = 322,
@@ -208,7 +211,7 @@ 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_DIFF_CHANNEL(16),
+ .chan = { LTC2378_DIFF_CHANNEL(16), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_DIFF_CHANNEL(16),
.max_sample_rate_Hz = 250 * HZ_PER_KHZ,
.tconv_ns = 3000,
@@ -216,7 +219,7 @@ 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_DIFF_CHANNEL(18),
+ .chan = { LTC2378_DIFF_CHANNEL(18), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_DIFF_CHANNEL(18),
.max_sample_rate_Hz = 250 * HZ_PER_KHZ,
.tconv_ns = 3000,
@@ -224,7 +227,7 @@ 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_DIFF_CHANNEL(20),
+ .chan = { LTC2378_DIFF_CHANNEL(20), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_DIFF_CHANNEL(20),
.max_sample_rate_Hz = 250 * HZ_PER_KHZ,
.tconv_ns = 3000,
@@ -232,7 +235,7 @@ 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_DIFF_CHANNEL(16),
+ .chan = { LTC2378_DIFF_CHANNEL(16), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_DIFF_CHANNEL(16),
.max_sample_rate_Hz = 500 * HZ_PER_KHZ,
.tconv_ns = 1500,
@@ -240,7 +243,7 @@ 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_DIFF_CHANNEL(18),
+ .chan = { LTC2378_DIFF_CHANNEL(18), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_DIFF_CHANNEL(18),
.max_sample_rate_Hz = 500 * HZ_PER_KHZ,
.tconv_ns = 1500,
@@ -248,7 +251,7 @@ 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_DIFF_CHANNEL(20),
+ .chan = { LTC2378_DIFF_CHANNEL(20), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_DIFF_CHANNEL(20),
.max_sample_rate_Hz = 500 * HZ_PER_KHZ,
.tconv_ns = 1500,
@@ -256,7 +259,7 @@ 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_DIFF_CHANNEL(16),
+ .chan = { LTC2378_DIFF_CHANNEL(16), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_DIFF_CHANNEL(16),
.max_sample_rate_Hz = 1 * HZ_PER_MHZ,
.tconv_ns = 527,
@@ -264,7 +267,7 @@ 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_DIFF_CHANNEL(18),
+ .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,
@@ -272,7 +275,7 @@ 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_DIFF_CHANNEL(20),
+ .chan = { LTC2378_DIFF_CHANNEL(20), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_DIFF_CHANNEL(20),
.max_sample_rate_Hz = 1 * HZ_PER_MHZ,
.tconv_ns = 675,
@@ -280,7 +283,7 @@ 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_DIFF_CHANNEL(18),
+ .chan = { LTC2378_DIFF_CHANNEL(18), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_DIFF_CHANNEL(18),
.max_sample_rate_Hz = 1600 * HZ_PER_KHZ,
.tconv_ns = 412,
@@ -288,7 +291,7 @@ 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_DIFF_CHANNEL(16),
+ .chan = { LTC2378_DIFF_CHANNEL(16), IIO_CHAN_SOFT_TIMESTAMP(1) },
.offload_chan = LTC2378_OFFLOAD_DIFF_CHANNEL(16),
.max_sample_rate_Hz = 2 * HZ_PER_MHZ,
.tconv_ns = 322,
@@ -307,6 +310,25 @@ 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)
{
@@ -671,8 +693,15 @@ 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 = <c2378_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
^ permalink raw reply related [flat|nested] 10+ messages in thread* [PATCH v9 5/6] iio: adc: ltc2378: Add support for LTC2338-18
2026-07-27 21:30 [PATCH v9 0/6] iio: adc: Add support for LTC2378 and similar ADCs Marcelo Schmitt
` (3 preceding siblings ...)
2026-07-27 21:31 ` [PATCH v9 4/6] iio: adc: ltc2378: Enable triggered buffer " Marcelo Schmitt
@ 2026-07-27 21:31 ` Marcelo Schmitt
2026-07-27 21:40 ` sashiko-bot
2026-07-27 21:32 ` [PATCH v9 6/6] iio: ABI: Encourage differential voltage ABI usage Marcelo Schmitt
5 siblings, 1 reply; 10+ messages in thread
From: Marcelo Schmitt @ 2026-07-27 21:31 UTC (permalink / raw)
To: linux-iio, devicetree, linux-kernel
Cc: jic23, nuno.sa, Michael.Hennerich, dlechner, andy, robh, krzk+dt,
conor+dt, julianbraha, marcelo.schmitt1
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>
---
New patch mainly extracted from the base driver patch with the addition of input
attenuation handling for LTC2338-18.
drivers/iio/adc/ltc2378.c | 44 ++++++++++++++++++++++++++++++++++++++-
1 file changed, 43 insertions(+), 1 deletion(-)
diff --git a/drivers/iio/adc/ltc2378.c b/drivers/iio/adc/ltc2378.c
index 146eaadbeb6c..689fa5419faf 100644
--- a/drivers/iio/adc/ltc2378.c
+++ b/drivers/iio/adc/ltc2378.c
@@ -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) },
@@ -383,7 +395,10 @@ static int ltc2378_read_raw(struct iio_dev *indio_dev,
return IIO_VAL_INT;
}
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:
@@ -641,6 +656,28 @@ 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 +713,10 @@ 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 +790,7 @@ static int ltc2378_probe(struct spi_device *spi)
}
static const struct of_device_id ltc2378_of_match[] = {
+ { .compatible = "adi,ltc2338-18", .data = <c2338_18_chip_info },
{ .compatible = "adi,ltc2364-16", .data = <c2364_16_chip_info },
{ .compatible = "adi,ltc2364-18", .data = <c2364_18_chip_info },
{ .compatible = "adi,ltc2367-16", .data = <c2367_16_chip_info },
@@ -774,6 +815,7 @@ 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)<c2338_18_chip_info },
{ .name = "ltc2364-16", .driver_data = (kernel_ulong_t)<c2364_16_chip_info },
{ .name = "ltc2364-18", .driver_data = (kernel_ulong_t)<c2364_18_chip_info },
{ .name = "ltc2367-16", .driver_data = (kernel_ulong_t)<c2367_16_chip_info },
--
2.53.0
^ permalink raw reply related [flat|nested] 10+ messages in thread* Re: [PATCH v9 5/6] iio: adc: ltc2378: Add support for LTC2338-18
2026-07-27 21:31 ` [PATCH v9 5/6] iio: adc: ltc2378: Add support for LTC2338-18 Marcelo Schmitt
@ 2026-07-27 21:40 ` sashiko-bot
0 siblings, 0 replies; 10+ messages in thread
From: sashiko-bot @ 2026-07-27 21:40 UTC (permalink / raw)
To: Marcelo Schmitt; +Cc: conor+dt, robh, devicetree
Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] Declaring a variable immediately after a switch case label without a block statement causes a compilation error.
--
--- Patch [5]: [PATCH v9 5/6] iio: adc: ltc2378: Add support for LTC2338-18 ---
commit 29728b1d34f34b2970657e2d83536de22940ee2e
Author: Marcelo Schmitt <marcelo.schmitt@analog.com>
iio: adc: ltc2378: Add support for LTC2338-18
This commit adds support for the LTC2338-18 ADC to the existing ltc2378
driver. It extends the driver to handle the internal voltage reference and
input signal attenuation specific to this part.
> diff --git a/drivers/iio/adc/ltc2378.c b/drivers/iio/adc/ltc2378.c
> --- a/drivers/iio/adc/ltc2378.c
> +++ b/drivers/iio/adc/ltc2378.c
[ ... ]
> @@ -383,7 +395,10 @@ static int ltc2378_read_raw(struct iio_dev *indio_dev,
> return IIO_VAL_INT;
> }
> case IIO_CHAN_INFO_SCALE:
> + struct u32_fract fract = st->info->internal_div;
[Severity: Low]
Does this declaration cause a build error? Declaring a variable immediately
after a switch case label without a block statement is not a valid statement
in C and usually causes a compiler error. Could this case be wrapped in a
block to scope the variable, or the declaration be moved to the top of the
function?
> *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:
--
Sashiko AI review · https://sashiko.dev/#/patchset/cover.1785186980.git.marcelo.schmitt@analog.com?part=5
^ permalink raw reply [flat|nested] 10+ messages in thread
* [PATCH v9 6/6] iio: ABI: Encourage differential voltage ABI usage
2026-07-27 21:30 [PATCH v9 0/6] iio: adc: Add support for LTC2378 and similar ADCs Marcelo Schmitt
` (4 preceding siblings ...)
2026-07-27 21:31 ` [PATCH v9 5/6] iio: adc: ltc2378: Add support for LTC2338-18 Marcelo Schmitt
@ 2026-07-27 21:32 ` Marcelo Schmitt
5 siblings, 0 replies; 10+ messages in thread
From: Marcelo Schmitt @ 2026-07-27 21:32 UTC (permalink / raw)
To: linux-iio, devicetree, linux-kernel
Cc: jic23, nuno.sa, Michael.Hennerich, dlechner, andy, robh, krzk+dt,
conor+dt, julianbraha, marcelo.schmitt1
So far, parts that could only do differential voltage measurements were
only required to have a consistent labeling of their channels by complying
either to voltageY or to voltageY-voltageZ ABI. Over time, code maintainers
came to the conclusion that the voltageY-voltageZ ABI is better suited for
differential-only chips as it provides a simple indication to users that
the channels measure the difference of two inputs.
Adjust the ABI documentation to recommend using the voltageY-voltageZ ABI
for chips that do only differential voltage measurements.
Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
---
No changes in v9.
Documentation/ABI/testing/sysfs-bus-iio | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
index 5cc2e82c4997..7446e07b9ab2 100644
--- a/Documentation/ABI/testing/sysfs-bus-iio
+++ b/Documentation/ABI/testing/sysfs-bus-iio
@@ -162,10 +162,11 @@ Contact: linux-iio@vger.kernel.org
Description:
Raw (unscaled) differential voltage measurement equivalent to
channel Y - channel Z where these channel numbers apply to the
- physically equivalent inputs when non differential readings are
- separately available. In differential only parts, then all that
- is required is a consistent labeling. Units after application
- of scale and offset are millivolts.
+ physically equivalent inputs when non-differential readings are
+ separately available. Even though differential-only parts had
+ been merely required to have consistent channel labeling, this
+ ABI is preferred over the non-differential one for those chips.
+ Units after application of scale and offset are millivolts.
What: /sys/bus/iio/devices/iio:deviceX/in_altvoltageY_rms_raw
KernelVersion: 6.18
--
2.53.0
^ permalink raw reply related [flat|nested] 10+ messages in thread