[PATCH v2 0/3] iio: adc: Add AD4134 minimum I/O support

[PATCH v2 0/3] iio: adc: Add AD4134 minimum I/O support

[Marcelo Schmitt]

This patch series adds basic support for ad4134. AD4134 is a very flexible
device that can be configured in many different ways. This series aims to
support the simplest way of interfacing with AD4134 which is called minimum I/O
mode in data sheet. This is essentially usual SPI with the addition of an ODR
(Output Data Rate) GPIO which functions as conversion start signal in minimum
I/O mode.

This set provides just one feature:
- Single-shot ADC sample read.

[PATCH 1] Device tree documentation for AD4134.
[PATCH 2] IIO Linux driver for AD4134.
[PATCH 3] Initial IIO documentation.

Change log v1 -> v2:
[Device tree]
- Dropped adi,control-mode property (can be inferred from the parent bus).
[IIO]
- Squashed the driver into a single file. Dropped unneeded code and simplified.
- Used IWYU to review includes (added missing ones, removed the unneeded).
- Reworked external clock setup.
- Dropped channel dynamic scan_types.
- Factored out register read specific code to into own function to make code more clear.
- Added comments to clarify non-intuitive code snippets.
- Added trailing commas where suggested.
- Made use of USEC_PER_SEC and HZ_PER_MHZ.
- Updated according to other suggestions (mostly code style).
[IIO Docs]
- Now using "~~~~~~~~" to mark fourth level topics.

Link to v1: https://lore.kernel.org/linux-iio/cover.1762777931.git.marcelo.schmitt@analog.com/

With best regards,
Marcelo


Marcelo Schmitt (3):
  dt-bindings: iio: adc: Add AD4134
  iio: adc: Initial support for AD4134
  Docs: iio: Add AD4134

 .../bindings/iio/adc/adi,ad4134.yaml          | 198 +++++++
 Documentation/iio/ad4134.rst                  |  58 +++
 Documentation/iio/index.rst                   |   1 +
 MAINTAINERS                                   |   9 +
 drivers/iio/adc/Kconfig                       |  11 +
 drivers/iio/adc/Makefile                      |   1 +
 drivers/iio/adc/ad4134.c                      | 493 ++++++++++++++++++
 7 files changed, 771 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml
 create mode 100644 Documentation/iio/ad4134.rst
 create mode 100644 drivers/iio/adc/ad4134.c


base-commit: f9e05791642810a0cf6237d39fafd6fec5e0b4bb
-- 
2.51.0

[PATCH v2 1/3] dt-bindings: iio: adc: Add AD4134

[Marcelo Schmitt]

Add device tree documentation for AD4134 24-Bit, 4-channel simultaneous
sampling, precision ADC.

Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
---
Change log v1 -> v2:
- Dropped adi,control-mode property (can be inferred from the parent bus).

adi,asrc-mode, adi,dclkio, adi,dclkmode, were also pondered for removal
since they are not needed for when AD4134 is connected to an SPI bus (current
use case). Though, since those properties will be needed for when AD4134 is not
connected to an SPI bus, I decided to keep them (based on v1 feedback [1]).

[1]: https://lore.kernel.org/linux-iio/20251114-unmasking-nerd-d5c147c43bad@spud/

 .../bindings/iio/adc/adi,ad4134.yaml          | 198 ++++++++++++++++++
 MAINTAINERS                                   |   7 +
 2 files changed, 205 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml

diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml
new file mode 100644
index 000000000000..6d17c0837c05
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml
@@ -0,0 +1,198 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/adc/adi,ad4134.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Analog Devices AD4134 ADC
+
+maintainers:
+  - Marcelo Schmitt <marcelo.schmitt@analog.com>
+
+description: |
+  The AD4134 is a quad channel, low noise, simultaneous sampling, precision
+  analog-to-digital converter (ADC).
+  Specifications can be found at:
+    https://www.analog.com/media/en/technical-documentation/data-sheets/ad4134.pdf
+
+$ref: /schemas/spi/spi-peripheral-props.yaml#
+
+properties:
+  compatible:
+    enum:
+      - adi,ad4134
+
+  reg:
+    maxItems: 1
+
+  spi-max-frequency:
+    maximum: 50000000
+
+  avdd5-supply:
+    description: A 5V supply that powers the chip's analog circuitry.
+
+  dvdd5-supply:
+    description: A 5V supply that powers the chip's digital circuitry.
+
+  iovdd-supply:
+    description:
+      A 1.8V supply that sets the logic levels for the digital interface pins.
+
+  refin-supply:
+    description:
+      A 4.096V or 5V supply that serves as reference for ADC conversions.
+
+  avdd1v8-supply:
+    description: A 1.8V supply used by the analog circuitry.
+
+  dvdd1v8-supply:
+    description: A 1.8V supply used by the digital circuitry.
+
+  clkvdd-supply:
+    description: A 1.8V supply for the chip's clock management circuit.
+
+  ldoin-supply:
+    description:
+      A 2.6V to 5.5V supply that generates 1.8V for AVDD1V8, DVDD1V8, and CLKVDD
+      pins.
+
+  clocks:
+    maxItems: 1
+    description:
+      Required external clock source. Can specify either a crystal or CMOS clock
+      source. If an external crystal is set, connect the CLKSEL pin to IOVDD.
+      Otherwise, connect the CLKSEL pin to IOGND and the external CMOS clock
+      signal to the XTAL2/CLKIN pin.
+
+  clock-names:
+    enum:
+      - xtal1-xtal2
+      - clkin
+    default: clkin
+
+  '#clock-cells':
+    const: 0
+
+  clock-output-names:
+    maxItems: 1
+
+  regulators:
+    type: object
+    description:
+      list of regulators provided by this controller.
+
+    properties:
+      vcm-output:
+        $ref: /schemas/regulator/regulator.yaml#
+        type: object
+        unevaluatedProperties: false
+
+    additionalProperties: false
+
+  reset-gpios:
+    maxItems: 1
+
+  powerdown-gpios:
+    description:
+      Active low GPIO connected to the /PDN pin. Forces the device into full
+      power-down mode when broght low. Pull this input to IOVDD for normal
+      operation.
+    maxItems: 1
+
+  odr-gpios:
+    description:
+      GPIO connected to ODR pin. Used to sample ADC data in minimum I/O mode.
+    maxItems: 1
+
+  adi,asrc-mode:
+    $ref: /schemas/types.yaml#/definitions/string
+    description:
+      Asynchronous Sample Rate Converter (ASRC) operation mode control input.
+      Describes whether the MODE pin is set to a high level (for master mode
+      operation) or to a low level (for slave mode operation).
+    enum: [ high, low ]
+    default: low
+
+  adi,dclkio:
+    description:
+      DCLK pin I/O direction control for when the device operates in Pin Control
+      Slave Mode or in SPI Control Mode. Describes if DEC0/DCLKIO pin is at a
+      high level (which configures DCLK as an output) or to set to a low level
+      (configuring DCLK for input).
+    enum: [ out, in ]
+    default: in
+
+  adi,dclkmode:
+    description:
+      DCLK mode control for when the device operates in Pin Control Slave Mode
+      or in SPI Control Mode. Describes whether the DEC1/DCLKMODE pin is set to
+      a high level (configuring the DCLK to operate in free running mode) or
+      to a low level (to configure DCLK to operate in gated mode).
+    enum: [ free-running, gated ]
+    default: gated
+
+required:
+  - compatible
+  - reg
+  - avdd5-supply
+  - dvdd5-supply
+  - iovdd-supply
+  - refin-supply
+  - clocks
+  - clock-names
+
+allOf:
+  - if:
+      not:
+        required:
+          - ldoin-supply
+    then:
+      required:
+        - avdd1v8-supply
+        - dvdd1v8-supply
+        - clkvdd-supply
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        adc@0 {
+            compatible = "adi,ad4134";
+            reg = <0>;
+
+            spi-max-frequency = <1000000>;
+
+            reset-gpios = <&gpio0 86 GPIO_ACTIVE_LOW>;
+            odr-gpios = <&gpio0 87 GPIO_ACTIVE_HIGH>;
+            powerdown-gpios = <&gpio0 88 GPIO_ACTIVE_LOW>;
+
+            clocks = <&sys_clk>;
+            clock-names = "clkin";
+
+            avdd5-supply = <&avdd5>;
+            dvdd5-supply = <&dvdd5>;
+            iovdd-supply = <&iovdd>;
+            refin-supply = <&refin>;
+            avdd1v8-supply = <&avdd1v8>;
+            dvdd1v8-supply = <&dvdd1v8>;
+            clkvdd-supply = <&clkvdd>;
+
+            adi,asrc-mode = "low";
+            adi,dclkio = "in";
+            adi,dclkmode = "gated";
+
+            regulators {
+                vcm_reg: vcm-output {
+                    regulator-name = "ad4134-vcm";
+                };
+            };
+
+        };
+    };
+...
diff --git a/MAINTAINERS b/MAINTAINERS
index 31d98efb1ad1..b9029c4055e3 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1449,6 +1449,13 @@ F:	Documentation/ABI/testing/sysfs-bus-iio-adc-ad4130
 F:	Documentation/devicetree/bindings/iio/adc/adi,ad4130.yaml
 F:	drivers/iio/adc/ad4130.c
 
+ANALOG DEVICES INC AD4134 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,ad4134.yaml
+
 ANALOG DEVICES INC AD4170-4 DRIVER
 M:	Marcelo Schmitt <marcelo.schmitt@analog.com>
 L:	linux-iio@vger.kernel.org
-- 
2.51.0

[PATCH v2 2/3] iio: adc: Initial support for AD4134

[Marcelo Schmitt]

AD4134 is a 24-bit, 4-channel, simultaneous sampling, precision
analog-to-digital converter (ADC). The device can be managed through SPI or
direct control of pin logical levels (pin control mode). The AD4134 design
also features a dedicated bus for ADC sample data output. Though, this
initial driver for AD4134 only supports usual SPI connections.

Add basic support for AD4134 that enables single-shot ADC sample read.

Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
---
Change log v1 -> v2:
- Squashed the driver into a single file. Dropped unneeded code and simplified.
- Used IWYU to review includes (added missing ones, removed the unneeded).
- Reworked external clock setup.
- Dropped channel dynamic scan_types.
- Factored out register read specific code to into own function to make code more clear.
- Added comments to clarify non-intuitive code snippets.
- Added trailing commas where suggested.
- Made use of USEC_PER_SEC and HZ_PER_MHZ.
- Updated according to other suggestions (mostly code style).

About the external clock handling, I personally prefer how it was in v1. For
these devices, we can't have two input clock sources connected simultaneously.
It's either a crystal or a CMOS clock, and we must have one of them. In other
words, the device will have one, and only one clock source at a time. Whether
the clock source comes from a crystal or other digital source is told by the
clock-names dt property. So we don't need to guess what type of clock we have.
We can get the correct clock according to firmware. I think that would make more
sense for ad4134 given we will have one, and necessarily one clock. The
suggested approach do work as expected, I just think it looks a bit clumsy IMHO.

CRC8 is needed because in minimum I/O mode SPI CRC is enabled and cannot be
disabled.

 MAINTAINERS              |   1 +
 drivers/iio/adc/Kconfig  |  11 +
 drivers/iio/adc/Makefile |   1 +
 drivers/iio/adc/ad4134.c | 493 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 506 insertions(+)
 create mode 100644 drivers/iio/adc/ad4134.c

diff --git a/MAINTAINERS b/MAINTAINERS
index b9029c4055e3..a1541cf3967b 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1455,6 +1455,7 @@ L:	linux-iio@vger.kernel.org
 S:	Supported
 W:	https://ez.analog.com/linux-software-drivers
 F:	Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml
+F:	drivers/iio/adc/ad4134.c
 
 ANALOG DEVICES INC AD4170-4 DRIVER
 M:	Marcelo Schmitt <marcelo.schmitt@analog.com>
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 58da8255525e..e711a146bd23 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -99,6 +99,17 @@ config AD4130
 	  To compile this driver as a module, choose M here: the module will be
 	  called ad4130.
 
+config AD4134
+	tristate "Analog Device AD4134 ADC Driver"
+	depends on SPI
+	select REGMAP_SPI
+	select CRC8
+	help
+	  Say yes here to build support for Analog Devices AD4134 SPI analog to
+	  digital converters (ADC).
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called ad4134_spi.
 
 config AD4170_4
 	tristate "Analog Device AD4170-4 ADC Driver"
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 7cc8f9a12f76..4f834b56e0f0 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -13,6 +13,7 @@ obj-$(CONFIG_AD4000) += ad4000.o
 obj-$(CONFIG_AD4030) += ad4030.o
 obj-$(CONFIG_AD4080) += ad4080.o
 obj-$(CONFIG_AD4130) += ad4130.o
+obj-$(CONFIG_AD4134) += ad4134.o
 obj-$(CONFIG_AD4170_4) += ad4170-4.o
 obj-$(CONFIG_AD4695) += ad4695.o
 obj-$(CONFIG_AD4851) += ad4851.o
diff --git a/drivers/iio/adc/ad4134.c b/drivers/iio/adc/ad4134.c
new file mode 100644
index 000000000000..e8a2d7fa161c
--- /dev/null
+++ b/drivers/iio/adc/ad4134.c
@@ -0,0 +1,493 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2025 Analog Devices, Inc.
+ * Author: Marcelo Schmitt <marcelo.schmitt@analog.com>
+ */
+
+#include <linux/array_size.h>
+#include <linux/bitfield.h>
+#include <linux/bitops.h>
+#include <linux/bits.h>
+#include <linux/clk.h>
+#include <linux/crc8.h>
+#include <linux/delay.h>
+#include <linux/dev_printk.h>
+#include <linux/err.h>
+#include <linux/export.h>
+#include <linux/gpio/consumer.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/types.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
+#include <linux/spi/spi.h>
+#include <linux/time.h>
+#include <linux/types.h>
+#include <linux/unaligned.h>
+#include <linux/units.h>
+
+#define AD4134_RESET_TIME_US			(10 * USEC_PER_SEC)
+
+#define AD4134_REG_READ_MASK			BIT(7)
+#define AD4134_SPI_MAX_XFER_LEN			3
+
+#define AD4134_EXT_CLOCK_MHZ			(48 * HZ_PER_MHZ)
+
+#define AD4134_NUM_CHANNELS			4
+#define AD4134_CHAN_PRECISION_BITS		24
+
+#define AD4134_IFACE_CONFIG_A_REG		0x00
+#define AD4134_IFACE_CONFIG_B_REG		0x01
+#define AD4134_IFACE_CONFIG_B_SINGLE_INSTR	BIT(7)
+
+#define AD4134_DEVICE_CONFIG_REG		0x02
+#define AD4134_DEVICE_CONFIG_POWER_MODE_MASK	BIT(0)
+#define AD4134_POWER_MODE_HIGH_PERF		0x1
+
+#define AD4134_SILICON_REV_REG			0x07
+#define AD4134_SCRATCH_PAD_REG			0x0A
+#define AD4134_STREAM_MODE_REG			0x0E
+#define AD4134_SDO_PIN_SRC_SEL_REG		0x10
+#define AD4134_SDO_PIN_SRC_SEL_SDO_SEL_MASK	BIT(2)
+
+#define AD4134_DATA_PACKET_CONFIG_REG		0x11
+#define AD4134_DATA_PACKET_CONFIG_FRAME_MASK	GENMASK(5, 4)
+#define AD4134_DATA_PACKET_24BIT_FRAME		0x2
+
+#define AD4134_DIG_IF_CFG_REG			0x12
+#define AD4134_DIF_IF_CFG_FORMAT_MASK		GENMASK(1, 0)
+#define AD4134_DATA_FORMAT_SINGLE_CH_MODE	0x0
+
+#define AD4134_PW_DOWN_CTRL_REG			0x13
+#define AD4134_DEVICE_STATUS_REG		0x15
+#define AD4134_ODR_VAL_INT_LSB_REG		0x16
+#define AD4134_CH3_OFFSET_MSB_REG		0x3E
+#define AD4134_AIN_OR_ERROR_REG			0x48
+
+/*
+ * AD4134 register map ends at address 0x48 and there is no register for
+ * retrieving ADC sample data. Though, to make use of Linux regmap API both
+ * for register access and sample read, we define one virtual register for each
+ * ADC channel. AD4134_CH_VREG(x) maps a channel number to it's virtual register
+ * address while AD4134_VREG_CH(x) tells which channel given the address.
+ */
+#define AD4134_CH_VREG(x)			((x) + 0x50)
+#define AD4134_VREG_CH(x)			((x) - 0x50)
+
+#define AD4134_SPI_CRC_POLYNOM			0x07
+#define AD4134_SPI_CRC_INIT_VALUE		0xA5
+static unsigned char ad4134_spi_crc_table[CRC8_TABLE_SIZE];
+
+#define AD4134_CHANNEL(_index) {						\
+	.type = IIO_VOLTAGE,							\
+	.indexed = 1,								\
+	.channel = (_index),							\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),				\
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),			\
+}
+
+static const struct iio_chan_spec ad4134_chan_set[] = {
+	AD4134_CHANNEL(0),
+	AD4134_CHANNEL(1),
+	AD4134_CHANNEL(2),
+	AD4134_CHANNEL(3),
+};
+
+struct ad4134_state {
+	struct spi_device *spi;
+	struct device *dev;
+	struct regmap *regmap;
+	unsigned long sys_clk_hz;
+	struct gpio_desc *odr_gpio;
+	int refin_mv;
+	/*
+	 * DMA (thus cache coherency maintenance) requires the transfer buffers
+	 * to live in their own cache lines.
+	 */
+	u8 rx_buf[AD4134_SPI_MAX_XFER_LEN] __aligned(IIO_DMA_MINALIGN);
+	u8 tx_buf[AD4134_SPI_MAX_XFER_LEN];
+};
+
+static const struct regmap_range ad4134_regmap_rd_range[] = {
+	regmap_reg_range(AD4134_IFACE_CONFIG_A_REG, AD4134_SILICON_REV_REG),
+	regmap_reg_range(AD4134_SCRATCH_PAD_REG, AD4134_PW_DOWN_CTRL_REG),
+	regmap_reg_range(AD4134_DEVICE_STATUS_REG, AD4134_AIN_OR_ERROR_REG),
+	regmap_reg_range(AD4134_CH_VREG(0), AD4134_CH_VREG(AD4134_NUM_CHANNELS)),
+};
+
+static const struct regmap_range ad4134_regmap_wr_range[] = {
+	regmap_reg_range(AD4134_IFACE_CONFIG_A_REG, AD4134_DEVICE_CONFIG_REG),
+	regmap_reg_range(AD4134_SCRATCH_PAD_REG, AD4134_SCRATCH_PAD_REG),
+	regmap_reg_range(AD4134_STREAM_MODE_REG, AD4134_PW_DOWN_CTRL_REG),
+	regmap_reg_range(AD4134_ODR_VAL_INT_LSB_REG, AD4134_CH3_OFFSET_MSB_REG),
+};
+
+static const struct regmap_access_table ad4134_regmap_rd_table = {
+	.yes_ranges = ad4134_regmap_rd_range,
+	.n_yes_ranges = ARRAY_SIZE(ad4134_regmap_rd_range),
+};
+
+static const struct regmap_access_table ad4134_regmap_wr_table = {
+	.yes_ranges = ad4134_regmap_wr_range,
+	.n_yes_ranges = ARRAY_SIZE(ad4134_regmap_wr_range),
+};
+
+static int ad4134_calc_spi_crc(u8 inst, u8 data)
+{
+	u8 buf[] = { inst, data };
+
+	return crc8(ad4134_spi_crc_table, buf, ARRAY_SIZE(buf),
+		    AD4134_SPI_CRC_INIT_VALUE);
+}
+
+static void ad4134_prepare_spi_tx_buf(u8 inst, u8 data, u8 *buf)
+{
+	buf[0] = inst;
+	buf[1] = data;
+	buf[2] = ad4134_calc_spi_crc(inst, data);
+}
+
+static int ad4134_reg_write(void *context, unsigned int reg, unsigned int val)
+{
+	struct ad4134_state *st = context;
+	struct spi_transfer xfer = {
+		.tx_buf = st->tx_buf,
+		.rx_buf = st->rx_buf,
+		.len = AD4134_SPI_MAX_XFER_LEN,
+	};
+	int ret;
+
+	ad4134_prepare_spi_tx_buf(reg, val, st->tx_buf);
+
+	ret = spi_sync_transfer(st->spi, &xfer, 1);
+	if (ret)
+		return ret;
+
+	if (st->rx_buf[2] != st->tx_buf[2])
+		dev_dbg(&st->spi->dev, "reg write CRC check failed\n");
+
+	return 0;
+}
+
+static int ad4134_data_read(struct ad4134_state *st, unsigned int reg,
+			    unsigned int *val)
+{
+	unsigned int i;
+	int ret;
+
+	/*
+	 * To be able to read data from all 4 channels through a single line, we
+	 * set DOUTx output format to 0 in the digital interface config register
+	 * (0x12). With that, data from all four channels is serialized and
+	 * output on DOUT0. During probe, we also set SDO_PIN_SRC_SEL in
+	 * DEVICE_CONFIG_1 register to duplicate DOUT0 on the SDO pin. Combined,
+	 * those configurations enable ADC data read through a conventional SPI
+	 * interface. Now we read data from all channels but keep only the bits
+	 * from the requested one.
+	 */
+	for (i = 0; i < ARRAY_SIZE(ad4134_chan_set); i++) {
+		ret = spi_write_then_read(st->spi, NULL, 0, st->rx_buf,
+					  BITS_TO_BYTES(AD4134_CHAN_PRECISION_BITS));
+		if (ret)
+			return ret;
+
+		if (i != AD4134_VREG_CH(reg))
+			continue;
+
+		*val = get_unaligned_be24(st->rx_buf);
+	}
+
+	return 0;
+}
+
+static int ad4134_register_read(struct ad4134_state *st, unsigned int reg,
+				unsigned int *val)
+{
+	struct spi_transfer xfer = {
+		.tx_buf = st->tx_buf,
+		.rx_buf = st->rx_buf,
+		.len = AD4134_SPI_MAX_XFER_LEN,
+	};
+	unsigned int inst;
+	int ret;
+
+	inst = AD4134_REG_READ_MASK | reg;
+	ad4134_prepare_spi_tx_buf(inst, 0, st->tx_buf);
+
+	ret = spi_sync_transfer(st->spi, &xfer, 1);
+	if (ret)
+		return ret;
+
+	*val = st->rx_buf[1];
+
+	/* Check CRC */
+	if (st->rx_buf[2] != st->tx_buf[2])
+		dev_dbg(&st->spi->dev, "reg read CRC check failed\n");
+
+	return 0;
+}
+
+static int ad4134_reg_read(void *context, unsigned int reg, unsigned int *val)
+{
+	struct ad4134_state *st = context;
+
+	if (reg >= AD4134_CH_VREG(0))
+		return ad4134_data_read(st, reg, val);
+
+	return ad4134_register_read(st, reg, val);
+}
+
+static const struct regmap_config ad4134_regmap_config = {
+	.reg_read = ad4134_reg_read,
+	.reg_write = ad4134_reg_write,
+	.rd_table = &ad4134_regmap_rd_table,
+	.wr_table = &ad4134_regmap_wr_table,
+	.max_register = AD4134_CH_VREG(ARRAY_SIZE(ad4134_chan_set)),
+};
+
+static int ad4134_read_raw(struct iio_dev *indio_dev,
+			   struct iio_chan_spec const *chan,
+			   int *val, int *val2, long info)
+{
+	struct ad4134_state *st = iio_priv(indio_dev);
+	int ret;
+
+	switch (info) {
+	case IIO_CHAN_INFO_RAW:
+		gpiod_set_value_cansleep(st->odr_gpio, 1);
+		fsleep(1);
+		gpiod_set_value_cansleep(st->odr_gpio, 0);
+		ret = regmap_read(st->regmap, AD4134_CH_VREG(chan->channel), val);
+		if (ret)
+			return ret;
+
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		*val = st->refin_mv;
+		*val2 = AD4134_CHAN_PRECISION_BITS - 1;
+
+		return IIO_VAL_FRACTIONAL_LOG2;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int ad4134_debugfs_reg_access(struct iio_dev *indio_dev,
+				     unsigned int reg, unsigned int writeval,
+				     unsigned int *readval)
+{
+	struct ad4134_state *st = iio_priv(indio_dev);
+
+	if (readval)
+		return regmap_read(st->regmap, reg, readval);
+
+	return regmap_write(st->regmap, reg, writeval);
+}
+
+static int ad4134_min_io_mode_setup(struct ad4134_state *st)
+{
+	struct device *dev = &st->spi->dev;
+	int ret;
+
+	st->odr_gpio = devm_gpiod_get(dev, "odr", GPIOD_OUT_LOW);
+	if (IS_ERR(st->odr_gpio))
+		return dev_err_probe(dev, PTR_ERR(st->odr_gpio),
+				     "failed to get ODR GPIO\n");
+
+	ret = regmap_update_bits(st->regmap, AD4134_DIG_IF_CFG_REG,
+				 AD4134_DIF_IF_CFG_FORMAT_MASK,
+				 FIELD_PREP(AD4134_DIF_IF_CFG_FORMAT_MASK,
+					    AD4134_DATA_FORMAT_SINGLE_CH_MODE));
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "failed to set single channel mode\n");
+
+	ret = regmap_set_bits(st->regmap, AD4134_SDO_PIN_SRC_SEL_REG,
+			      AD4134_SDO_PIN_SRC_SEL_SDO_SEL_MASK);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "failed to set SDO source selection\n");
+
+	return regmap_set_bits(st->regmap, AD4134_IFACE_CONFIG_B_REG,
+			       AD4134_IFACE_CONFIG_B_SINGLE_INSTR);
+}
+
+static const struct iio_info ad4134_info = {
+	.read_raw = ad4134_read_raw,
+	.debugfs_reg_access = ad4134_debugfs_reg_access,
+};
+
+static const char * const ad4143_regulator_names[] = {
+	"avdd5", "dvdd5", "iovdd", "refin",
+	"avdd1v8", "dvdd1v8", "clkvdd",	"ldoin",
+};
+
+static int ad4134_regulator_setup(struct ad4134_state *st)
+{
+	struct device *dev = &st->spi->dev;
+	bool use_internal_ldo_regulator;
+	int ret;
+
+	/* Required regulators */
+	ret = devm_regulator_bulk_get_enable(dev, 3, ad4143_regulator_names);
+	if (ret)
+		return dev_err_probe(dev, ret, "failed to enable power supplies\n");
+
+	/* Required regulator that we need to read the voltage */
+	ret = devm_regulator_get_enable_read_voltage(dev, "refin");
+	if (ret < 0)
+		return dev_err_probe(dev, ret, "failed to get REFIN voltage.\n");
+
+	st->refin_mv = ret / MILLI;
+
+	/*
+	 * If ldoin is not provided, then avdd1v8, dvdd1v8, and clkvdd are
+	 * required.
+	 */
+	ret = devm_regulator_get_enable_optional(dev, "ldoin");
+	if (ret < 0 && ret != -ENODEV)
+		return dev_err_probe(dev, ret, "failed to enable ldoin supply\n");
+
+	use_internal_ldo_regulator = ret == 0;
+
+	if (!use_internal_ldo_regulator) {
+		ret = devm_regulator_get_enable(dev, "avdd1v8");
+		if (ret < 0)
+			return dev_err_probe(dev, ret,
+					     "failed to enable avdd1v8 supply\n");
+
+		ret = devm_regulator_get_enable(dev, "dvdd1v8");
+		if (ret < 0)
+			return dev_err_probe(dev, ret,
+					     "failed to enable dvdd1v8 supply\n");
+
+		ret = devm_regulator_get_enable(dev, "clkvdd");
+		if (ret < 0)
+			return dev_err_probe(dev, ret,
+					     "failed to enable clkvdd supply\n");
+	}
+
+	return 0;
+}
+
+static int ad4134_clock_select(struct ad4134_state *st)
+{
+	struct device *dev = &st->spi->dev;
+	struct clk *sys_clk;
+	int ret;
+
+	sys_clk = devm_clk_get_optional_enabled(dev, "xtal1-xtal2");
+	if (IS_ERR_OR_NULL(sys_clk)) {
+		ret = PTR_ERR_OR_ZERO(sys_clk);
+		sys_clk = devm_clk_get_enabled(dev, "clkin");
+		if (IS_ERR(sys_clk))
+			return dev_err_probe(dev, PTR_ERR(sys_clk),
+					     "failed to get xtal1-xtal2: %d, clkin: %ld\n",
+					     ret, PTR_ERR(sys_clk));
+	}
+
+	st->sys_clk_hz = clk_get_rate(sys_clk);
+	if (st->sys_clk_hz != AD4134_EXT_CLOCK_MHZ)
+		dev_warn(dev, "invalid external clock frequency %lu\n",
+			 st->sys_clk_hz);
+
+	return 0;
+}
+
+static int ad4134_probe(struct spi_device *spi)
+{
+	struct device *dev = &spi->dev;
+	struct gpio_desc *reset_gpio;
+	struct iio_dev *indio_dev;
+	struct ad4134_state *st;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	st = iio_priv(indio_dev);
+	st->spi = spi;
+
+	indio_dev->name = "ad4134";
+	indio_dev->channels = ad4134_chan_set;
+	indio_dev->num_channels = ARRAY_SIZE(ad4134_chan_set);
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->info = &ad4134_info;
+
+	ret = ad4134_regulator_setup(st);
+	if (ret)
+		return ret;
+
+	ret = ad4134_clock_select(st);
+	if (ret)
+		return ret;
+
+	reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(reset_gpio))
+		return dev_err_probe(dev, PTR_ERR(reset_gpio),
+				     "failed to find reset GPIO\n");
+
+	if (reset_gpio) {
+		fsleep(AD4134_RESET_TIME_US);
+		gpiod_set_value_cansleep(reset_gpio, 0);
+	}
+
+	crc8_populate_msb(ad4134_spi_crc_table, AD4134_SPI_CRC_POLYNOM);
+
+	st->regmap = devm_regmap_init(dev, NULL, st, &ad4134_regmap_config);
+	if (IS_ERR(st->regmap))
+		return dev_err_probe(dev, PTR_ERR(st->regmap),
+				     "failed to initialize regmap");
+
+	ret = ad4134_min_io_mode_setup(st);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "failed to setup minimum I/O mode\n");
+
+	/* Bump precision to 24-bit */
+	ret = regmap_update_bits(st->regmap, AD4134_DATA_PACKET_CONFIG_REG,
+				 AD4134_DATA_PACKET_CONFIG_FRAME_MASK,
+				 FIELD_PREP(AD4134_DATA_PACKET_CONFIG_FRAME_MASK,
+					    AD4134_DATA_PACKET_24BIT_FRAME));
+	if (ret)
+		return ret;
+
+	/* Set high performance power mode */
+	ret = regmap_update_bits(st->regmap, AD4134_DEVICE_CONFIG_REG,
+				 AD4134_DEVICE_CONFIG_POWER_MODE_MASK,
+				 FIELD_PREP(AD4134_DEVICE_CONFIG_POWER_MODE_MASK,
+					    AD4134_POWER_MODE_HIGH_PERF));
+	if (ret)
+		return ret;
+
+	return devm_iio_device_register(dev, indio_dev);
+}
+
+static const struct spi_device_id ad4134_id[] = {
+	{ "ad4134" },
+	{ }
+};
+MODULE_DEVICE_TABLE(spi, ad4134_id);
+
+static const struct of_device_id ad4134_of_match[] = {
+	{ .compatible = "adi,ad4134" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ad4134_of_match);
+
+static struct spi_driver ad4134_driver = {
+	.driver = {
+		.name = "ad4134",
+		.of_match_table = ad4134_of_match,
+	},
+	.probe = ad4134_probe,
+	.id_table = ad4134_id,
+};
+module_spi_driver(ad4134_driver);
+
+MODULE_AUTHOR("Marcelo Schmitt <marcelo.schmitt@analog.com>");
+MODULE_DESCRIPTION("Analog Devices AD4134 SPI driver");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS("IIO_AD4134");
-- 
2.51.0

[PATCH v2 3/3] Docs: iio: Add AD4134

[Marcelo Schmitt]

Add initial documentation for the ad4134 IIO driver.

Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
---
Change log v1 -> v2:
- Now using "~~~~~~~~" to mark fourth level topic.

 Documentation/iio/ad4134.rst | 58 ++++++++++++++++++++++++++++++++++++
 Documentation/iio/index.rst  |  1 +
 MAINTAINERS                  |  1 +
 3 files changed, 60 insertions(+)
 create mode 100644 Documentation/iio/ad4134.rst

diff --git a/Documentation/iio/ad4134.rst b/Documentation/iio/ad4134.rst
new file mode 100644
index 000000000000..fa44a05e6793
--- /dev/null
+++ b/Documentation/iio/ad4134.rst
@@ -0,0 +1,58 @@
+.. SPDX-License-Identifier: GPL-2.0-only
+
+=============
+AD4134 driver
+=============
+
+Device driver for Analog Devices Inc. AD4134 and similar ADCs.
+
+Supported devices
+=================
+
+* `AD4134 <https://www.analog.com/AD4134>`_
+* `AD7134 <https://www.analog.com/AD7134>`_
+
+Wiring connections
+------------------
+
+AD4134 and similar ADCs can operate in a few different wiring configurations.
+
+Minimum I/O mode (SPI control mode)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The minimum I/O mode wiring allows AD4134 register and data access with the
+conventional set of SPI bus lines. The hardware configuration settings for using
+AD4134 in minimum I/O mode are:
+
++----------------------------+----------------------+--------------------+
+| Pin Function               |         Level        | Description        |
++============================+======================+====================+
+| PIN/SPI                    |         High         | SPI control mode   |
++----------------------------+----------------------+--------------------+
+| MODE                       |         Low          | ASRC slave mode    |
++----------------------------+----------------------+--------------------+
+| DCLKIO                     |         Low          | DCLK input         |
++----------------------------+----------------------+--------------------+
+| DCLKMODE                   |         Low          | Gated DCLK         |
++----------------------------+----------------------+--------------------+
+
+A possible connection schema that sets AD4134 digital interface for minimum I/O
+mode is:
+
+::
+
+                                 IOVDD
+      +------------------------+   |
+      |                PIN/SPI |<--+     +-------------+
+      |                        |         |     HOST    |
+      |                   DCLK |<--+     |             |
+      |           FORMAT1/SCLK |<--+---- | SCLK        |
+      |   AD4134      DEC2/SDI |<--------| SDO         |
+      |               DEC3/SDO |-------->| SDI         |
+      |                    ODR |<--------| GPIO        |
+      |             FORMAT0/CS |<--+     |             |
+      |                   MODE |<--+     +-------------+
+      |            DEC0/DCLKIO |<--+
+      |          DEC1/DCLKMODE |<--+
+      +------------------------+   |
+                                  GND
diff --git a/Documentation/iio/index.rst b/Documentation/iio/index.rst
index 315ae37d6fd4..d4ed782c93a6 100644
--- a/Documentation/iio/index.rst
+++ b/Documentation/iio/index.rst
@@ -22,6 +22,7 @@ Industrial I/O Kernel Drivers
    ad3552r
    ad4000
    ad4030
+   ad4134
    ad4695
    ad7191
    ad7380
diff --git a/MAINTAINERS b/MAINTAINERS
index a1541cf3967b..b2c101598636 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1455,6 +1455,7 @@ L:	linux-iio@vger.kernel.org
 S:	Supported
 W:	https://ez.analog.com/linux-software-drivers
 F:	Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml
+F:	Documentation/iio/ad4134.rst
 F:	drivers/iio/adc/ad4134.c
 
 ANALOG DEVICES INC AD4170-4 DRIVER
-- 
2.51.0

Re: [PATCH v2 2/3] iio: adc: Initial support for AD4134

[Andy Shevchenko]

On Tue, Nov 18, 2025 at 02:32:43PM -0300, Marcelo Schmitt wrote:
> AD4134 is a 24-bit, 4-channel, simultaneous sampling, precision
> analog-to-digital converter (ADC). The device can be managed through SPI or
> direct control of pin logical levels (pin control mode). The AD4134 design
> also features a dedicated bus for ADC sample data output. Though, this
> initial driver for AD4134 only supports usual SPI connections.
> 
> Add basic support for AD4134 that enables single-shot ADC sample read.

Thanks for an update! My comments below.

...

> +#include <linux/array_size.h>
> +#include <linux/bitfield.h>
> +#include <linux/bitops.h>
> +#include <linux/bits.h>

bitops.h implies bits.h and the latter can be omitted. But it's up to you, I'm
fine with the current way.

> +#include <linux/clk.h>
> +#include <linux/crc8.h>
> +#include <linux/delay.h>
> +#include <linux/dev_printk.h>
> +#include <linux/err.h>
> +#include <linux/export.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/types.h>
> +#include <linux/module.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/regmap.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/spi/spi.h>
> +#include <linux/time.h>
> +#include <linux/types.h>
> +#include <linux/unaligned.h>
> +#include <linux/units.h>

...

> +struct ad4134_state {

> +	struct spi_device *spi;
> +	struct device *dev;
> +	struct regmap *regmap;

We have a duplication here, I believe. Either struct device or struct regmap
may be dropped. If it's not the case, the fields needs a good description /
justification.

> +	unsigned long sys_clk_hz;
> +	struct gpio_desc *odr_gpio;
> +	int refin_mv;
> +	/*
> +	 * DMA (thus cache coherency maintenance) requires the transfer buffers
> +	 * to live in their own cache lines.
> +	 */
> +	u8 rx_buf[AD4134_SPI_MAX_XFER_LEN] __aligned(IIO_DMA_MINALIGN);
> +	u8 tx_buf[AD4134_SPI_MAX_XFER_LEN];
> +};

...

> +static int ad4134_regulator_setup(struct ad4134_state *st)
> +{
> +	struct device *dev = &st->spi->dev;
> +	bool use_internal_ldo_regulator;
> +	int ret;
> +
> +	/* Required regulators */
> +	ret = devm_regulator_bulk_get_enable(dev, 3, ad4143_regulator_names);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "failed to enable power supplies\n");
> +
> +	/* Required regulator that we need to read the voltage */
> +	ret = devm_regulator_get_enable_read_voltage(dev, "refin");
> +	if (ret < 0)
> +		return dev_err_probe(dev, ret, "failed to get REFIN voltage.\n");

> +	st->refin_mv = ret / MILLI;

I think the divisor should be (MICRO / MILLI). This what Jonathan suggested
last time I remember (in some other reviews).

> +	/*
> +	 * If ldoin is not provided, then avdd1v8, dvdd1v8, and clkvdd are
> +	 * required.
> +	 */
> +	ret = devm_regulator_get_enable_optional(dev, "ldoin");
> +	if (ret < 0 && ret != -ENODEV)
> +		return dev_err_probe(dev, ret, "failed to enable ldoin supply\n");
> +
> +	use_internal_ldo_regulator = ret == 0;

> +	if (!use_internal_ldo_regulator) {

Can it be

	if (use_internal_ldo_regulator)
		return 0;

with the dropped indentation level for the below?


> +		ret = devm_regulator_get_enable(dev, "avdd1v8");
> +		if (ret < 0)
> +			return dev_err_probe(dev, ret,
> +					     "failed to enable avdd1v8 supply\n");
> +
> +		ret = devm_regulator_get_enable(dev, "dvdd1v8");
> +		if (ret < 0)
> +			return dev_err_probe(dev, ret,
> +					     "failed to enable dvdd1v8 supply\n");
> +
> +		ret = devm_regulator_get_enable(dev, "clkvdd");
> +		if (ret < 0)
> +			return dev_err_probe(dev, ret,
> +					     "failed to enable clkvdd supply\n");
> +	}
> +
> +	return 0;
> +}

...

> +static int ad4134_clock_select(struct ad4134_state *st)
> +{
> +	struct device *dev = &st->spi->dev;
> +	struct clk *sys_clk;
> +	int ret;

> +	sys_clk = devm_clk_get_optional_enabled(dev, "xtal1-xtal2");

> +	if (IS_ERR_OR_NULL(sys_clk)) {

I don't understand the choice of _optional() with the _NULL here.
Also note, we missed the deferred probe case here.

Was it me who suggested this? :-)

One solution may be to check the clock name presence in the clock-names or
whatever the name of that DT property before trying to get this clock.

> +		ret = PTR_ERR_OR_ZERO(sys_clk);
> +		sys_clk = devm_clk_get_enabled(dev, "clkin");
> +		if (IS_ERR(sys_clk))

Yeah, v1 might look better, but I don't remember by heart.

> +			return dev_err_probe(dev, PTR_ERR(sys_clk),
> +					     "failed to get xtal1-xtal2: %d, clkin: %ld\n",
> +					     ret, PTR_ERR(sys_clk));

No need to have a duplicated error code being printed.

> +	}
> +
> +	st->sys_clk_hz = clk_get_rate(sys_clk);
> +	if (st->sys_clk_hz != AD4134_EXT_CLOCK_MHZ)
> +		dev_warn(dev, "invalid external clock frequency %lu\n",
> +			 st->sys_clk_hz);
> +
> +	return 0;
> +}

...

> +	reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
> +	if (IS_ERR(reset_gpio))
> +		return dev_err_probe(dev, PTR_ERR(reset_gpio),
> +				     "failed to find reset GPIO\n");
> +
> +	if (reset_gpio) {
> +		fsleep(AD4134_RESET_TIME_US);

> +		gpiod_set_value_cansleep(reset_gpio, 0);
> +	}

Can we use reset-gpio driver instead of custom implementation?

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2 1/3] dt-bindings: iio: adc: Add AD4134

[Conor Dooley]

[-- Attachment #1: Type: text/plain, Size: 383 bytes --]

On Tue, Nov 18, 2025 at 02:32:22PM -0300, Marcelo Schmitt wrote:
> +  powerdown-gpios:
> +    description:
> +      Active low GPIO connected to the /PDN pin. Forces the device into full
> +      power-down mode when broght low. Pull this input to IOVDD for normal
> +      operation.

s/broght/brought/

Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
pw-bot: not-applicable

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