[PATCH v3 0/3] iio: adc: ad4695: new driver for AD4695 and similar ADCs

[PATCH v3 0/3] iio: adc: ad4695: new driver for AD4695 and similar ADCs

[David Lechner]

This is adding DT bindings and a new driver for the AD4695 and similar
devices. The plan is to implement quite a few more features, but this
is a complex chip so we're spreading out the work. To start with, we
have a reasonably complete DT binding and a very basic driver.

This work is being done in collaboration with Analog Devices Inc.,
hence they listed as maintainers rather than me. The code has been
tested on a ZedBoard with an EVAL-AD4696FMCZ using the internal LDO,
an external reference and a variety of input channel configurations.

---
Changes in v3:
* Dropped "dt-bindings: iio: adc: add common-mode-channel dependency"
  patch.
* Link to v2: https://lore.kernel.org/r/20240617-iio-adc-ad4695-v2-0-63ef6583f25d@baylibre.com

[PATCH 1/3]
* Change interrupts to be per pin instead of per signal.
* Drop diff-channels and single-channel properties.
* Odd numbered pins added to common-mode-channel property enum.
* REFGND and COM values changed to avoid confusion with pin numbers.
* Add inX-supply properties for odd numbed input pins.

[PATCH 2/3]
* always include all channels, not just ones customized in DT
* rework channel fwnode parsing for DT changes

[PATCH 3/3]
* Rework DT examples for DT bindings changes

Changes in v2:

[PATCH 1/4]
* New patch
* Depends on recently applied patch
  https://lore.kernel.org/linux-iio/20240607-ad4111-v7-1-97e3855900a0@analog.com/

[PATCH 2/4]
* Drop *-wlcsp compatible strings
* Don't use fallback compatible strings
* Reword supply descriptions
* Use standard channel properties instead of adi,pin-pairing
* Fix unnecessary | character
* Fix missing blank line
* Add header file with common mode channel macros

[PATCH 3/4]
* rework register definition macros
* remove code structure comments at top level
* remove simple wrapper functions around regmap functions
* rework channel fwnode parsing for DT changes
* fix missing return value check

[PATCH 4/4]
* Rework DT examples for DT bindings changes
* Fix wrong MAINTAINERS update

* Link to v1: https://lore.kernel.org/r/20240612-iio-adc-ad4695-v1-0-6a4ed251fc86@baylibre.com

---
David Lechner (3):
      dt-bindings: iio: adc: add AD4695 and similar ADCs
      iio: adc: ad4695: Add driver for AD4695 and similar ADCs
      Documentation: iio: Document ad4695 driver

 .../devicetree/bindings/iio/adc/adi,ad4695.yaml    | 256 ++++++++
 Documentation/iio/ad4695.rst                       | 155 +++++
 Documentation/iio/index.rst                        |   1 +
 MAINTAINERS                                        |  12 +
 drivers/iio/adc/Kconfig                            |  11 +
 drivers/iio/adc/Makefile                           |   1 +
 drivers/iio/adc/ad4695.c                           | 730 +++++++++++++++++++++
 include/dt-bindings/iio/adi,ad4695.h               |   9 +
 8 files changed, 1175 insertions(+)
---
base-commit: 2dfa1b7bfc07e58acb9f9eaa8c871f37189dbfee
change-id: 20240517-iio-adc-ad4695-ef72b2a2cf88

Best regards,
-- 
David Lechner <dlechner@baylibre.com>

[PATCH v3 1/3] dt-bindings: iio: adc: add AD4695 and similar ADCs

[David Lechner]

Add device tree bindings for AD4695 and similar ADCs.

Signed-off-by: David Lechner <dlechner@baylibre.com>
---

Note, this may trigger a DT build warning "common-mode-channel: missing
type definition" if the builder doesn't include the recently added
common-mode-channel property [1]. This should be safe to ignore (passes
make dt_binding_check locally).

[1] https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git/commit/?h=testing&id=d86deaec1c5b0fb60c3619e8d2ae7a1d722fd2ad

v3 changes:
* Change interrupts to be per pin instead of per signal.
* Drop diff-channels and single-channel properties.
* Odd numbered pins added to common-mode-channel property enum.
* REFGND and COM values changes to avoid confusion with pin numbers.
* Add inX-supply properties for odd numbed input pins.

v2 changes:
* Drop *-wlcsp compatible strings
* Don't use fallback compatible strings
* Reword supply descriptions
* Use standard channel properties instead of adi,pin-pairing
* Fix unnecessary | character
* Fix missing blank line
* Add header file with common mode channel macros
---
 .../devicetree/bindings/iio/adc/adi,ad4695.yaml    | 256 +++++++++++++++++++++
 MAINTAINERS                                        |  10 +
 include/dt-bindings/iio/adi,ad4695.h               |   9 +
 3 files changed, 275 insertions(+)

diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad4695.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad4695.yaml
new file mode 100644
index 000000000000..a2e824e26691
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/adc/adi,ad4695.yaml
@@ -0,0 +1,256 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/adc/adi,ad4695.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Analog Devices Easy Drive Multiplexed SAR Analog to Digital Converters
+
+maintainers:
+  - Michael Hennerich <Michael.Hennerich@analog.com>
+  - Nuno Sá <nuno.sa@analog.com>
+
+description: |
+  A family of similar multi-channel analog to digital converters with SPI bus.
+
+  * https://www.analog.com/en/products/ad4695.html
+  * https://www.analog.com/en/products/ad4696.html
+  * https://www.analog.com/en/products/ad4697.html
+  * https://www.analog.com/en/products/ad4698.html
+
+$ref: /schemas/spi/spi-peripheral-props.yaml#
+
+properties:
+  compatible:
+    enum:
+      - adi,ad4695
+      - adi,ad4696
+      - adi,ad4697
+      - adi,ad4698
+
+  reg:
+    maxItems: 1
+
+  spi-max-frequency:
+    maximum: 80000000
+
+  spi-cpol: true
+  spi-cpha: true
+
+  spi-rx-bus-width:
+    minimum: 1
+    maximum: 4
+
+  avdd-supply:
+    description: Analog power supply.
+
+  vio-supply:
+    description: I/O pin power supply.
+
+  ldo-in-supply:
+    description: Internal LDO Input. Mutually exclusive with vdd-supply.
+
+  vdd-supply:
+    description: Core power supply. Mutually exclusive with ldo-in-supply.
+
+  ref-supply:
+    description:
+      External reference voltage. Mutually exclusive with refin-supply.
+
+  refin-supply:
+    description:
+      Internal reference buffer input. Mutually exclusive with ref-supply.
+
+  com-supply:
+    description: Common voltage supply for pseudo-differential analog inputs.
+
+  adi,no-ref-current-limit:
+    $ref: /schemas/types.yaml#/definitions/flag
+    description:
+      When this flag is present, the REF Overvoltage Reduced Current protection
+      is disabled.
+
+  adi,no-ref-high-z:
+    $ref: /schemas/types.yaml#/definitions/flag
+    description:
+      Enable this flag if the ref-supply requires Reference Input High-Z Mode
+      to be disabled for proper operation.
+
+  cnv-gpios:
+    description: The Convert Input (CNV). If omitted, CNV is tied to SPI CS.
+    maxItems: 1
+
+  reset-gpios:
+    description: The Reset Input (RESET). Should be configured GPIO_ACTIVE_LOW.
+    maxItems: 1
+
+  interrupts:
+    minItems: 1
+    items:
+      - description: Signal coming from the BSY_ALT_GP0 pin (ALERT or BUSY).
+      - description: Signal coming from the GP2 pin (ALERT).
+      - description: Signal coming from the GP3 pin (BUSY).
+
+  interrupt-names:
+    minItems: 1
+    items:
+      - const: gp0
+      - const: gp2
+      - const: gp3
+
+  gpio-controller: true
+
+  "#gpio-cells":
+    const: 2
+    description: |
+      The first cell is the GPn number: 0 to 3.
+      The second cell takes standard GPIO flags.
+
+  "#address-cells":
+    const: 1
+
+  "#size-cells":
+    const: 0
+
+patternProperties:
+  "^in(?:[13579]|1[135])-supply$":
+    description:
+      Optional voltage supply for odd numbered channels when they are used as
+      the negative input for a pseudo-differential channel.
+
+  "^channel@[0-9a-f]$":
+    type: object
+    $ref: adc.yaml
+    unevaluatedProperties: false
+    description:
+      Describes each individual channel. In addition the properties defined
+      below, bipolar from adc.yaml is also supported.
+
+    properties:
+      reg:
+        maximum: 15
+
+      common-mode-channel:
+        description:
+          Describes the common mode channel for single channels. 0xFF is REFGND
+          and OxFE is COM. Macros are available for these values in
+          dt-bindings/iio/adi,ad4695.h. Values 1 to 15 correspond to INx inputs.
+          Only odd numbered INx inputs can be used as common mode channels.
+        items:
+          enum: [1, 3, 5, 7, 9, 11, 13, 15, 0xFE, 0xFF]
+        default: 0xFF
+
+      adi,no-high-z:
+        $ref: /schemas/types.yaml#/definitions/flag
+        description:
+          Enable this flag if the input pin requires the Analog Input High-Z
+          Mode to be disabled for proper operation.
+
+    required:
+      - reg
+
+    allOf:
+      # bipolar mode can't be used with REFGND
+      - if:
+          properties:
+            common-mode-channel:
+              const: 0xFF
+        then:
+          properties:
+            bipolar: false
+
+required:
+  - compatible
+  - reg
+  - avdd-supply
+  - vio-supply
+
+allOf:
+  - oneOf:
+      - required:
+          - ldo-in-supply
+      - required:
+          - vdd-supply
+
+  - oneOf:
+      - required:
+          - ref-supply
+      - required:
+          - refin-supply
+
+  # the internal reference buffer always requires high-z mode
+  - if:
+      required:
+        - refin-supply
+    then:
+      properties:
+        adi,no-ref-high-z: false
+
+  # limit channels for 8-channel chips
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - adi,ad4697
+              - adi,ad4698
+    then:
+      patternProperties:
+        "^in(?:9|1[135])-supply$": false
+        "^channel@[0-7]$":
+          properties:
+            reg:
+              maximum: 7
+            common-mode-channel:
+              items:
+                enum: [1, 3, 5, 7, 0xFE, 0xFF]
+        "^channel@[8-9a-f]$": false
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    #include <dt-bindings/iio/adi,ad4695.h>
+
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        adc@0 {
+            compatible = "adi,ad4695";
+            reg = <0>;
+            spi-cpol;
+            spi-cpha;
+            spi-max-frequency = <80000000>;
+            avdd-supply = <&power_supply>;
+            ldo-in-supply = <&power_supply>;
+            vio-supply = <&io_supply>;
+            refin-supply = <&supply_5V>;
+            com-supply = <&supply_2V5>;
+            in3-supply = <&supply_2V5>;
+            reset-gpios = <&gpio 1 GPIO_ACTIVE_LOW>;
+
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            /* Pseudo-differential channel between IN0 and REFGND. */
+            channel@0 {
+                reg = <0>;
+            };
+
+            /* Pseudo-differential channel between IN1 and COM. */
+            channel@1 {
+                reg = <1>;
+                common-mode-channel = <AD4695_COMMON_MODE_COM>;
+                bipolar;
+            };
+
+            /* Pseudo-differential channel between IN2 and IN3. */
+            channel@2 {
+                reg = <2>;
+                common-mode-channel = <3>;
+                bipolar;
+            };
+        };
+    };
diff --git a/MAINTAINERS b/MAINTAINERS
index 9517093d889d..025ee138a713 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1208,6 +1208,16 @@ 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 AD4695 DRIVER
+M:	Michael Hennerich <michael.hennerich@analog.com>
+M:	Nuno Sá <nuno.sa@analog.com>
+R:	David Lechner <dlechner@baylibre.com>
+L:	linux-iio@vger.kernel.org
+S:	Supported
+W:	https://ez.analog.com/linux-software-drivers
+F:	Documentation/devicetree/bindings/iio/adc/adi,ad4695.yaml
+F:	include/dt-bindings/iio/adi,ad4695.h
+
 ANALOG DEVICES INC AD7091R DRIVER
 M:	Marcelo Schmitt <marcelo.schmitt@analog.com>
 L:	linux-iio@vger.kernel.org
diff --git a/include/dt-bindings/iio/adi,ad4695.h b/include/dt-bindings/iio/adi,ad4695.h
new file mode 100644
index 000000000000..9fbef542bf67
--- /dev/null
+++ b/include/dt-bindings/iio/adi,ad4695.h
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) */
+
+#ifndef _DT_BINDINGS_ADI_AD4695_H
+#define _DT_BINDINGS_ADI_AD4695_H
+
+#define AD4695_COMMON_MODE_REFGND	0xFF
+#define AD4695_COMMON_MODE_COM		0xFE
+
+#endif /* _DT_BINDINGS_ADI_AD4695_H */

-- 
2.45.2

[PATCH v3 2/3] iio: adc: ad4695: Add driver for AD4695 and similar ADCs

[David Lechner]

This is a new driver for Analog Devices Inc. AD4695 and similar ADCs.
The initial driver supports initializing the chip including configuring
all possible LDO and reference voltage sources as well as any possible
voltage input channel wiring configuration.

Only the 4-wire SPI wiring mode where the CNV pin is tied to the CS pin
is supported at this time. And reading sample data from the ADC can only
be done in direct mode for now.

Co-developed-by: Ramona Gradinariu <ramona.gradinariu@analog.com>
Signed-off-by: Ramona Gradinariu <ramona.gradinariu@analog.com>
Signed-off-by: David Lechner <dlechner@baylibre.com>
---

v3 changes:
* always include all channels, not just ones customized in DT
* rework channel fwnode parsing for DT changes

v2 changes:
* rework register definition macros
* remove code structure comments at top level
* remove simple wrapper functions around regmap functions
* rework channel fwnode parsing for DT changes
* fix missing return value check
---
 MAINTAINERS              |   1 +
 drivers/iio/adc/Kconfig  |  11 +
 drivers/iio/adc/Makefile |   1 +
 drivers/iio/adc/ad4695.c | 730 +++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 743 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 025ee138a713..c52c4b0e69a8 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1216,6 +1216,7 @@ L:	linux-iio@vger.kernel.org
 S:	Supported
 W:	https://ez.analog.com/linux-software-drivers
 F:	Documentation/devicetree/bindings/iio/adc/adi,ad4695.yaml
+F:	drivers/iio/adc/ad4695.c
 F:	include/dt-bindings/iio/adi,ad4695.h
 
 ANALOG DEVICES INC AD7091R DRIVER
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index b8184706c7d1..eed5547a5078 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -36,6 +36,17 @@ config AD4130
 	  To compile this driver as a module, choose M here: the module will be
 	  called ad4130.
 
+config AD4695
+	tristate "Analog Device AD4695 ADC Driver"
+	depends on SPI
+	select REGMAP_SPI
+	help
+	  Say yes here to build support for Analog Devices AD4695 and similar
+	  analog to digital converters (ADC).
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called ad4695.
+
 config AD7091R
 	tristate
 
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 51298c52b223..c180c85b6327 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -7,6 +7,7 @@
 obj-$(CONFIG_AB8500_GPADC) += ab8500-gpadc.o
 obj-$(CONFIG_AD_SIGMA_DELTA) += ad_sigma_delta.o
 obj-$(CONFIG_AD4130) += ad4130.o
+obj-$(CONFIG_AD4695) += ad4695.o
 obj-$(CONFIG_AD7091R) += ad7091r-base.o
 obj-$(CONFIG_AD7091R5) += ad7091r5.o
 obj-$(CONFIG_AD7091R8) += ad7091r8.o
diff --git a/drivers/iio/adc/ad4695.c b/drivers/iio/adc/ad4695.c
new file mode 100644
index 000000000000..72ab5b997f6e
--- /dev/null
+++ b/drivers/iio/adc/ad4695.c
@@ -0,0 +1,730 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * SPI ADC driver for Analog Devices Inc. AD4695 and similar chips
+ *
+ * https://www.analog.com/en/products/ad4695.html
+ * https://www.analog.com/en/products/ad4696.html
+ * https://www.analog.com/en/products/ad4697.html
+ * https://www.analog.com/en/products/ad4698.html
+ *
+ * Copyright 2024 Analog Devices Inc.
+ * Copyright 2024 BayLibre, SAS
+ */
+
+#include <dt-bindings/iio/adi,ad4695.h>
+#include <linux/bitfield.h>
+#include <linux/bits.h>
+#include <linux/compiler.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/iio/iio.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
+#include <linux/spi/spi.h>
+#include <linux/units.h>
+
+/* AD4695 registers */
+#define AD4695_REG_SPI_CONFIG_A				0x0000
+#define   AD4695_REG_SPI_CONFIG_A_SW_RST		  (BIT(7) | BIT(0))
+#define AD4695_REG_SPI_CONFIG_B				0x0001
+#define   AD4695_REG_SPI_CONFIG_B_INST_MODE		  BIT(7)
+#define AD4695_REG_DEVICE_TYPE				0x0003
+#define AD4695_REG_SCRATCH_PAD				0x000A
+#define AD4695_REG_VENDOR_L				0x000C
+#define AD4695_REG_VENDOR_H				0x000D
+#define AD4695_REG_LOOP_MODE				0x000E
+#define AD4695_REG_SPI_CONFIG_C				0x0010
+#define   AD4695_REG_SPI_CONFIG_C_MB_STRICT		  BIT(7)
+#define AD4695_REG_SPI_STATUS				0x0011
+#define AD4695_REG_STATUS				0x0014
+#define AD4695_REG_ALERT_STATUS1			0x0015
+#define AD4695_REG_ALERT_STATUS2			0x0016
+#define AD4695_REG_CLAMP_STATUS				0x001A
+#define AD4695_REG_SETUP				0x0020
+#define   AD4695_REG_SETUP_LDO_EN			  BIT(4)
+#define   AD4695_REG_SETUP_SPI_MODE			  BIT(2)
+#define   AD4695_REG_SETUP_SPI_CYC_CTRL			  BIT(1)
+#define AD4695_REG_REF_CTRL				0x0021
+#define   AD4695_REG_REF_CTRL_OV_MODE			  BIT(7)
+#define   AD4695_REG_REF_CTRL_VREF_SET			  GENMASK(4, 2)
+#define   AD4695_REG_REF_CTRL_REFHIZ_EN			  BIT(1)
+#define   AD4695_REG_REF_CTRL_REFBUF_EN			  BIT(0)
+#define AD4695_REG_SEQ_CTRL				0x0022
+#define   AD4695_REG_SEQ_CTRL_STD_SEQ_EN		  BIT(7)
+#define   AD4695_REG_SEQ_CTRL_NUM_SLOTS_AS		  GENMASK(6, 0)
+#define AD4695_REG_AC_CTRL				0x0023
+#define AD4695_REG_STD_SEQ_CONFIG			0x0024
+#define AD4695_REG_GPIO_CTRL				0x0026
+#define AD4695_REG_GP_MODE				0x0027
+#define AD4695_REG_TEMP_CTRL				0x0029
+#define AD4695_REG_CONFIG_IN(n)				(0x0030 | (n))
+#define   AD4695_REG_CONFIG_IN_MODE			  BIT(6)
+#define   AD4695_REG_CONFIG_IN_PAIR			  GENMASK(5, 4)
+#define   AD4695_REG_CONFIG_IN_AINHIGHZ_EN		  BIT(3)
+#define AD4695_REG_UPPER_IN(n)				(0x0040 | (2 * (n)))
+#define AD4695_REG_LOWER_IN(n)				(0x0060 | (2 * (n)))
+#define AD4695_REG_HYST_IN(n)				(0x0080 | (2 * (n)))
+#define AD4695_REG_OFFSET_IN(n)				(0x00A0 | (2 * (n)))
+#define AD4695_REG_GAIN_IN(n)				(0x00C0 | (2 * (n)))
+#define AD4695_REG_AS_SLOT(n)				(0x0100 | (n))
+#define   AD4695_REG_AS_SLOT_INX			  GENMASK(3, 0)
+#define AD4695_MAX_REG					0x017F
+
+/* Conversion mode commands */
+#define AD4695_CMD_EXIT_CNV_MODE	0x0A
+#define AD4695_CMD_TEMP_CHAN		0x0F
+#define AD4695_CMD_VOLTAGE_CHAN(n)	(0x10 | (n))
+
+/* timing specs */
+#define AD4695_T_CONVERT_NS		415
+#define AD4695_T_WAKEUP_HW_MS		3
+#define AD4695_T_WAKEUP_SW_MS		3
+#define AD4695_T_REFBUF_MS		100
+#define AD4695_REG_ACCESS_SCLK_HZ	(10 * MEGA)
+
+#define AD4695_MAX_CHANNELS		16
+
+enum ad4695_in_pair {
+	AD4695_IN_PAIR_REFGND,
+	AD4695_IN_PAIR_COM,
+	AD4695_IN_PAIR_EVEN_ODD,
+};
+
+struct ad4695_chip_info {
+	const char *name;
+	int max_sample_rate;
+	u8 num_voltage_inputs;
+};
+
+struct ad4695_channel_config {
+	unsigned int channel;
+	bool highz_en;
+	bool bipolar;
+	enum ad4695_in_pair pin_pairing;
+	unsigned int common_mode_mv;
+};
+
+struct ad4695_state {
+	struct spi_device *spi;
+	struct regmap *regmap;
+	struct gpio_desc *reset_gpio;
+	struct iio_chan_spec iio_chan[AD4695_MAX_CHANNELS + 1];
+	struct ad4695_channel_config channels_cfg[AD4695_MAX_CHANNELS];
+	const struct ad4695_chip_info *chip_info;
+	/* Reference voltage. */
+	unsigned int vref_mv;
+	/* Common mode input pin voltage. */
+	unsigned int com_mv;
+	/* raw data conversion data received */
+	u16 raw_data __aligned(IIO_DMA_MINALIGN);
+	/* Commands to send for single conversion */
+	u16 cnv_cmd;
+	u8 cnv_cmd2;
+};
+
+static const struct regmap_range ad4695_regmap_rd_ranges[] = {
+	regmap_reg_range(AD4695_REG_SPI_CONFIG_A, AD4695_REG_SPI_CONFIG_B),
+	regmap_reg_range(AD4695_REG_DEVICE_TYPE, AD4695_REG_DEVICE_TYPE),
+	regmap_reg_range(AD4695_REG_SCRATCH_PAD, AD4695_REG_SCRATCH_PAD),
+	regmap_reg_range(AD4695_REG_VENDOR_L, AD4695_REG_LOOP_MODE),
+	regmap_reg_range(AD4695_REG_SPI_CONFIG_C, AD4695_REG_SPI_STATUS),
+	regmap_reg_range(AD4695_REG_STATUS, AD4695_REG_ALERT_STATUS2),
+	regmap_reg_range(AD4695_REG_CLAMP_STATUS, AD4695_REG_CLAMP_STATUS),
+	regmap_reg_range(AD4695_REG_SETUP, AD4695_REG_TEMP_CTRL),
+	regmap_reg_range(AD4695_REG_CONFIG_IN(0), AD4695_MAX_REG),
+};
+
+static const struct regmap_access_table ad4695_regmap_rd_table = {
+	.yes_ranges = ad4695_regmap_rd_ranges,
+	.n_yes_ranges = ARRAY_SIZE(ad4695_regmap_rd_ranges),
+};
+
+static const struct regmap_range ad4695_regmap_wr_ranges[] = {
+	regmap_reg_range(AD4695_REG_SPI_CONFIG_A, AD4695_REG_SPI_CONFIG_B),
+	regmap_reg_range(AD4695_REG_SCRATCH_PAD, AD4695_REG_SCRATCH_PAD),
+	regmap_reg_range(AD4695_REG_LOOP_MODE, AD4695_REG_LOOP_MODE),
+	regmap_reg_range(AD4695_REG_SPI_CONFIG_C, AD4695_REG_SPI_STATUS),
+	regmap_reg_range(AD4695_REG_SETUP, AD4695_REG_TEMP_CTRL),
+	regmap_reg_range(AD4695_REG_CONFIG_IN(0), AD4695_MAX_REG),
+};
+
+static const struct regmap_access_table ad4695_regmap_wr_table = {
+	.yes_ranges = ad4695_regmap_wr_ranges,
+	.n_yes_ranges = ARRAY_SIZE(ad4695_regmap_wr_ranges),
+};
+
+static const struct regmap_config ad4695_regmap_config = {
+	.name = "ad4695",
+	.reg_bits = 16,
+	.val_bits = 8,
+	.max_register = AD4695_MAX_REG,
+	.rd_table = &ad4695_regmap_rd_table,
+	.wr_table = &ad4695_regmap_wr_table,
+	.can_multi_write = true,
+};
+
+static const struct iio_chan_spec ad4695_channel_template = {
+	.type = IIO_VOLTAGE,
+	.indexed = 1,
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+			      BIT(IIO_CHAN_INFO_SCALE) |
+			      BIT(IIO_CHAN_INFO_OFFSET),
+	.scan_type = {
+		.sign = 'u',
+		.realbits = 16,
+		.storagebits = 16,
+	},
+};
+
+static const struct iio_chan_spec ad4695_temp_channel_template = {
+	.address = AD4695_CMD_TEMP_CHAN,
+	.type = IIO_TEMP,
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+			      BIT(IIO_CHAN_INFO_SCALE) |
+			      BIT(IIO_CHAN_INFO_OFFSET),
+	.scan_type = {
+		.sign = 's',
+		.realbits = 16,
+		.storagebits = 16,
+	},
+};
+
+static const char * const ad4695_power_supplies[] = {
+	"avdd", "vio"
+};
+
+static const struct ad4695_chip_info ad4695_chip_info = {
+	.name = "ad4695",
+	.max_sample_rate = 500 * KILO,
+	.num_voltage_inputs = 16,
+};
+
+static const struct ad4695_chip_info ad4696_chip_info = {
+	.name = "ad4696",
+	.max_sample_rate = 1 * MEGA,
+	.num_voltage_inputs = 16,
+};
+
+static const struct ad4695_chip_info ad4697_chip_info = {
+	.name = "ad4697",
+	.max_sample_rate = 500 * KILO,
+	.num_voltage_inputs = 8,
+};
+
+static const struct ad4695_chip_info ad4698_chip_info = {
+	.name = "ad4698",
+	.max_sample_rate = 1 * MEGA,
+	.num_voltage_inputs = 8,
+};
+
+/**
+ * ad4695_set_single_cycle_mode - Set the device in single cycle mode
+ * @st: The AD4695 state
+ * @channel: The first channel to read
+ *
+ * As per the datasheet, to enable single cycle mode, we need to set
+ * STD_SEQ_EN=0, NUM_SLOTS_AS=0 and CYC_CTRL=1 (Table 15). Setting SPI_MODE=1
+ * triggers the first conversion using the channel in AS_SLOT0.
+ *
+ * Context: can sleep, must be called with iio_device_claim_direct held
+ * Return: 0 on success, a negative error code on failure
+ */
+static int ad4695_set_single_cycle_mode(struct ad4695_state *st,
+					unsigned int channel)
+{
+	int ret;
+
+	ret = regmap_clear_bits(st->regmap, AD4695_REG_SEQ_CTRL,
+				AD4695_REG_SEQ_CTRL_STD_SEQ_EN |
+				AD4695_REG_SEQ_CTRL_NUM_SLOTS_AS);
+	if (ret)
+		return ret;
+
+	ret = regmap_write(st->regmap, AD4695_REG_AS_SLOT(0),
+			   FIELD_PREP(AD4695_REG_AS_SLOT_INX, channel));
+	if (ret)
+		return ret;
+
+	return regmap_set_bits(st->regmap, AD4695_REG_SETUP,
+			       AD4695_REG_SETUP_SPI_MODE |
+			       AD4695_REG_SETUP_SPI_CYC_CTRL);
+}
+
+static int ad4695_set_ref_voltage(struct ad4695_state *st, int vref_mv)
+{
+	u8 val;
+
+	if (vref_mv >= 2400 && vref_mv <= 2750)
+		val = 0;
+	else if (vref_mv > 2750 && vref_mv <= 3250)
+		val = 1;
+	else if (vref_mv > 3250 && vref_mv <= 3750)
+		val = 2;
+	else if (vref_mv > 3750 && vref_mv <= 4500)
+		val = 3;
+	else if (vref_mv > 4500 && vref_mv <= 5100)
+		val = 4;
+	else
+		return -EINVAL;
+
+	return regmap_update_bits(st->regmap, AD4695_REG_REF_CTRL,
+				  AD4695_REG_REF_CTRL_VREF_SET,
+				  FIELD_PREP(AD4695_REG_REF_CTRL_VREF_SET, val));
+}
+
+static int ad4695_write_chn_cfg(struct ad4695_state *st,
+				struct ad4695_channel_config *cfg)
+{
+	u32 mask = 0, val = 0;
+
+	mask |= AD4695_REG_CONFIG_IN_MODE;
+	val |= FIELD_PREP(AD4695_REG_CONFIG_IN_MODE, cfg->bipolar ? 1 : 0);
+
+	mask |= AD4695_REG_CONFIG_IN_PAIR;
+	val |= FIELD_PREP(AD4695_REG_CONFIG_IN_PAIR, cfg->pin_pairing);
+
+	mask |= AD4695_REG_CONFIG_IN_AINHIGHZ_EN;
+	val |= FIELD_PREP(AD4695_REG_CONFIG_IN_AINHIGHZ_EN, cfg->highz_en ? 1 : 0);
+
+	return regmap_update_bits(st->regmap, AD4695_REG_CONFIG_IN(cfg->channel),
+				  mask, val);
+}
+
+/**
+ * ad4695_read_one_sample - Read a single sample using single-cycle mode
+ * @st: The AD4695 state
+ * @address: The address of the channel to read
+ *
+ * Upon return, the sample will be stored in the raw_data field of @st.
+ *
+ * Context: can sleep, must be called with iio_device_claim_direct held
+ * Return: 0 on success, a negative error code on failure
+ */
+static int ad4695_read_one_sample(struct ad4695_state *st, unsigned int address)
+{
+	struct spi_transfer xfer[2] = { };
+	int ret;
+
+	ret = ad4695_set_single_cycle_mode(st, address);
+	if (ret)
+		return ret;
+
+	/*
+	 * Setting the first channel to the temperature channel isn't supported
+	 * in single-cycle mode, so we have to do an extra xfer to read the
+	 * temperature.
+	 */
+	if (address == AD4695_CMD_TEMP_CHAN) {
+		/* We aren't reading, so we can make this a short xfer. */
+		st->cnv_cmd2 = AD4695_CMD_TEMP_CHAN << 3;
+		xfer[0].bits_per_word = 8;
+		xfer[0].tx_buf = &st->cnv_cmd2;
+		xfer[0].len = 1;
+		xfer[0].cs_change = 1;
+		xfer[0].cs_change_delay.value = AD4695_T_CONVERT_NS;
+		xfer[0].cs_change_delay.unit = SPI_DELAY_UNIT_NSECS;
+
+		/* Then read the result and exit conversion mode. */
+		st->cnv_cmd = AD4695_CMD_EXIT_CNV_MODE << 11;
+		xfer[1].bits_per_word = 16;
+		xfer[1].tx_buf = &st->cnv_cmd;
+		xfer[1].rx_buf = &st->raw_data;
+		xfer[1].len = 2;
+
+		return spi_sync_transfer(st->spi, xfer, 2);
+	}
+
+	/*
+	 * The conversion has already been done and we just have to read the
+	 * result and exit conversion mode.
+	 */
+	st->cnv_cmd = AD4695_CMD_EXIT_CNV_MODE << 11;
+	xfer[0].bits_per_word = 16;
+	xfer[0].tx_buf = &st->cnv_cmd;
+	xfer[0].rx_buf = &st->raw_data;
+	xfer[0].len = 2;
+
+	return spi_sync_transfer(st->spi, xfer, 1);
+}
+
+static int ad4695_read_raw(struct iio_dev *indio_dev,
+			   struct iio_chan_spec const *chan,
+			   int *val, int *val2, long mask)
+{
+	struct ad4695_state *st = iio_priv(indio_dev);
+	struct ad4695_channel_config *cfg = &st->channels_cfg[chan->scan_index];
+	u8 realbits = chan->scan_type.realbits;
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		iio_device_claim_direct_scoped(return -EBUSY, indio_dev) {
+			ret = ad4695_read_one_sample(st, chan->address);
+			if (ret)
+				return ret;
+
+			if (chan->scan_type.sign == 's')
+				*val = sign_extend32(st->raw_data, realbits - 1);
+			else
+				*val = st->raw_data;
+
+			return IIO_VAL_INT;
+		}
+		unreachable();
+	case IIO_CHAN_INFO_SCALE:
+		switch (chan->type) {
+		case IIO_VOLTAGE:
+			*val = st->vref_mv;
+			*val2 = chan->scan_type.realbits;
+			return IIO_VAL_FRACTIONAL_LOG2;
+		case IIO_TEMP:
+			/* T_scale (°C) = raw * V_REF (mV) / (-1.8 mV/°C * 2^16) */
+			*val = st->vref_mv * -556;
+			*val2 = 16;
+			return IIO_VAL_FRACTIONAL_LOG2;
+		default:
+			return -EINVAL;
+		}
+	case IIO_CHAN_INFO_OFFSET:
+		switch (chan->type) {
+		case IIO_VOLTAGE:
+			if (cfg->pin_pairing == AD4695_IN_PAIR_COM)
+				*val = st->com_mv * (1 << realbits) / st->vref_mv;
+			else if (cfg->pin_pairing == AD4695_IN_PAIR_EVEN_ODD)
+				*val = cfg->common_mode_mv * (1 << realbits) / st->vref_mv;
+			else
+				*val = 0;
+
+			return IIO_VAL_INT;
+		case IIO_TEMP:
+			/* T_offset (°C) = -725 mV / (-1.8 mV/°C) */
+			/* T_offset (raw) = T_offset (°C) * (-1.8 mV/°C) * 2^16 / V_REF (mV) */
+			*val = -47513600;
+			*val2 = st->vref_mv;
+			return IIO_VAL_FRACTIONAL;
+		default:
+			return -EINVAL;
+		}
+	default:
+		return -EINVAL;
+	}
+}
+
+static int ad4695_debugfs_reg_access(struct iio_dev *indio_dev, unsigned int reg,
+				     unsigned int writeval, unsigned int *readval)
+{
+	struct ad4695_state *st = iio_priv(indio_dev);
+
+	iio_device_claim_direct_scoped(return -EBUSY, indio_dev) {
+		if (readval)
+			return regmap_read(st->regmap, reg, readval);
+
+		return regmap_write(st->regmap, reg, writeval);
+	}
+
+	unreachable();
+}
+
+static const struct iio_info ad4695_info = {
+	.read_raw = &ad4695_read_raw,
+	.debugfs_reg_access = &ad4695_debugfs_reg_access,
+};
+
+static int ad4695_parse_channel_cfg(struct iio_dev *indio_dev)
+{
+	struct device *dev = indio_dev->dev.parent;
+	struct ad4695_state *st = iio_priv(indio_dev);
+	struct ad4695_channel_config *chan_cfg;
+	struct iio_chan_spec *iio_chan;
+	int ret, i;
+
+	/* populate defaults */
+	for (i = 0; i < st->chip_info->num_voltage_inputs; i++) {
+		chan_cfg = &st->channels_cfg[i];
+		iio_chan = &st->iio_chan[i];
+
+		chan_cfg->highz_en = true;
+		chan_cfg->channel = i;
+
+		*iio_chan = ad4695_channel_template;
+		iio_chan->channel = i;
+		iio_chan->scan_index = i;
+		iio_chan->address = AD4695_CMD_VOLTAGE_CHAN(i);
+	}
+
+	/* modify based on firmware description */
+	device_for_each_child_node_scoped(dev, child) {
+		u32 reg, val;
+
+		ret = fwnode_property_read_u32(child, "reg", &reg);
+		if (ret)
+			return dev_err_probe(dev, ret,
+				"failed to read reg property (%s)\n",
+				fwnode_get_name(child));
+
+		if (reg >= st->chip_info->num_voltage_inputs)
+			return dev_err_probe(dev, -EINVAL,
+				"reg out of range (%s)\n",
+				fwnode_get_name(child));
+
+		iio_chan = &st->iio_chan[reg];
+		chan_cfg = &st->channels_cfg[reg];
+
+		chan_cfg->highz_en = !fwnode_property_read_bool(child, "adi,no-high-z");
+		chan_cfg->bipolar = fwnode_property_read_bool(child, "bipolar");
+
+		ret = fwnode_property_read_u32(child, "common-mode-channel", &val);
+		if (ret && ret != -EINVAL)
+			return dev_err_probe(dev, ret,
+				"failed to read common-mode-channel (%s)\n",
+				fwnode_get_name(child));
+
+		if (ret == -EINVAL || val == AD4695_COMMON_MODE_REFGND)
+			chan_cfg->pin_pairing = AD4695_IN_PAIR_REFGND;
+		else if (val == AD4695_COMMON_MODE_COM)
+			chan_cfg->pin_pairing = AD4695_IN_PAIR_COM;
+		else
+			chan_cfg->pin_pairing = AD4695_IN_PAIR_EVEN_ODD;
+
+		if (chan_cfg->pin_pairing == AD4695_IN_PAIR_EVEN_ODD &&
+		    val % 2 == 0)
+			return dev_err_probe(dev, -EINVAL,
+				"common-mode-channel must be odd number (%s)\n",
+				fwnode_get_name(child));
+
+		if (chan_cfg->pin_pairing == AD4695_IN_PAIR_EVEN_ODD &&
+		    val != reg + 1)
+			return dev_err_probe(dev, -EINVAL,
+				"common-mode-channel must be next consecutive channel (%s)\n",
+				fwnode_get_name(child));
+
+		if (chan_cfg->pin_pairing == AD4695_IN_PAIR_EVEN_ODD) {
+			char name[5];
+
+			snprintf(name, sizeof(name), "in%d", reg + 1);
+
+			ret = devm_regulator_get_enable_read_voltage(dev, name);
+			if (ret < 0)
+				return dev_err_probe(dev, ret,
+					"failed to get %s voltage (%s)\n",
+					name, fwnode_get_name(child));
+
+			chan_cfg->common_mode_mv = ret / 1000;
+		}
+
+		if (chan_cfg->bipolar && chan_cfg->pin_pairing == AD4695_IN_PAIR_REFGND)
+			return dev_err_probe(dev, -EINVAL,
+				"bipolar mode is not available for inputs paired with REFGND (%s).\n",
+				fwnode_get_name(child));
+
+		if (chan_cfg->bipolar)
+			iio_chan->scan_type.sign = 's';
+
+		ret = ad4695_write_chn_cfg(st, chan_cfg);
+		if (ret)
+			return ret;
+	}
+
+	/* Temperature channel must be next scan index after voltage channels. */
+	st->iio_chan[i] = ad4695_temp_channel_template;
+	st->iio_chan[i].scan_index = i;
+
+	return 0;
+}
+
+static int ad4695_probe(struct spi_device *spi)
+{
+	struct device *dev = &spi->dev;
+	struct ad4695_state *st;
+	struct iio_dev *indio_dev;
+	struct gpio_desc *cnv_gpio;
+	bool use_internal_ldo_supply;
+	bool use_internal_ref_buffer;
+	int ret;
+
+	cnv_gpio = devm_gpiod_get_optional(dev, "cnv", GPIOD_OUT_LOW);
+	if (IS_ERR(cnv_gpio))
+		return dev_err_probe(dev, PTR_ERR(cnv_gpio), "Failed to get CNV GPIO\n");
+
+	/* Driver currently requires CNV pin to be connected to SPI CS */
+	if (cnv_gpio)
+		return dev_err_probe(dev, -ENODEV, "CNV GPIO is not supported\n");
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	st = iio_priv(indio_dev);
+	st->spi = spi;
+
+	st->chip_info = spi_get_device_match_data(spi);
+	if (!st->chip_info)
+		return -EINVAL;
+
+	/* Registers cannot be read at the max allowable speed */
+	spi->max_speed_hz = AD4695_REG_ACCESS_SCLK_HZ;
+
+	st->regmap = devm_regmap_init_spi(spi, &ad4695_regmap_config);
+	if (IS_ERR(st->regmap))
+		return dev_err_probe(dev, PTR_ERR(st->regmap), "Failed to initialize regmap\n");
+
+	ret = devm_regulator_bulk_get_enable(dev, ARRAY_SIZE(ad4695_power_supplies),
+					     ad4695_power_supplies);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to enable power supplies\n");
+
+	/* If LDO_IN supply is present, then we are using internal LDO. */
+	ret = devm_regulator_get_enable_optional(dev, "ldo-in");
+	if (ret < 0 && ret != -ENODEV)
+		return dev_err_probe(dev, ret, "Failed to enable LDO_IN supply\n");
+
+	use_internal_ldo_supply = ret == 0;
+
+	if (!use_internal_ldo_supply) {
+		/* Otherwise we need an external VDD supply. */
+		ret = devm_regulator_get_enable(dev, "vdd");
+		if (ret < 0)
+			return dev_err_probe(dev, ret, "Failed to enable VDD supply\n");
+	}
+
+	/* If REFIN supply is given, then we are using internal buffer */
+	ret = devm_regulator_get_enable_read_voltage(dev, "refin");
+	if (ret < 0 && ret != -ENODEV)
+		return dev_err_probe(dev, ret, "Failed to get REFIN voltage\n");
+
+	if (ret != -ENODEV) {
+		st->vref_mv = ret / 1000;
+		use_internal_ref_buffer = true;
+	} else {
+		/* Otherwise, we need an external reference. */
+		ret = devm_regulator_get_enable_read_voltage(dev, "ref");
+		if (ret < 0)
+			return dev_err_probe(dev, ret, "Failed to get REF voltage\n");
+
+		st->vref_mv = ret / 1000;
+		use_internal_ref_buffer = false;
+	}
+
+	ret = devm_regulator_get_enable_read_voltage(dev, "com");
+	if (ret < 0 && ret != -ENODEV)
+		return dev_err_probe(dev, ret, "Failed to get COM voltage\n");
+
+	st->com_mv = ret == -ENODEV ? 0 : ret / 1000;
+
+	/*
+	 * Reset the device using hardware reset if available or fall back to
+	 * software reset.
+	 */
+
+	st->reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(st->reset_gpio))
+		return PTR_ERR(st->reset_gpio);
+
+	if (st->reset_gpio) {
+		gpiod_set_value(st->reset_gpio, 0);
+		msleep(AD4695_T_WAKEUP_HW_MS);
+	} else {
+		ret = regmap_write(st->regmap, AD4695_REG_SPI_CONFIG_A,
+				   AD4695_REG_SPI_CONFIG_A_SW_RST);
+		if (ret)
+			return ret;
+
+		msleep(AD4695_T_WAKEUP_SW_MS);
+	}
+
+	/* Needed for debugfs since it only access registers 1 byte at a time. */
+	ret = regmap_set_bits(st->regmap, AD4695_REG_SPI_CONFIG_C,
+			      AD4695_REG_SPI_CONFIG_C_MB_STRICT);
+	if (ret)
+		return ret;
+
+	/* Disable internal LDO if it isn't needed. */
+	ret = regmap_update_bits(st->regmap, AD4695_REG_SETUP,
+				 AD4695_REG_SETUP_LDO_EN,
+				 FIELD_PREP(AD4695_REG_SETUP_LDO_EN,
+					    use_internal_ldo_supply ? 1 : 0));
+	if (ret)
+		return ret;
+
+	/* configure reference supply */
+
+	if (device_property_present(dev, "adi,no-ref-current-limit")) {
+		ret = regmap_set_bits(st->regmap, AD4695_REG_REF_CTRL,
+				      AD4695_REG_REF_CTRL_OV_MODE);
+		if (ret)
+			return ret;
+	}
+
+	if (device_property_present(dev, "adi,no-ref-high-z")) {
+		if (use_internal_ref_buffer)
+			return dev_err_probe(dev, -EINVAL,
+				"Cannot disable high-Z mode for internal reference buffer\n");
+
+		ret = regmap_clear_bits(st->regmap, AD4695_REG_REF_CTRL,
+					AD4695_REG_REF_CTRL_REFHIZ_EN);
+		if (ret)
+			return ret;
+	}
+
+	ret = ad4695_set_ref_voltage(st, st->vref_mv);
+	if (ret)
+		return ret;
+
+	if (use_internal_ref_buffer) {
+		ret = regmap_set_bits(st->regmap, AD4695_REG_REF_CTRL,
+				      AD4695_REG_REF_CTRL_REFBUF_EN);
+		if (ret)
+			return ret;
+
+		/* Give the capacitor some time to charge up. */
+		msleep(AD4695_T_REFBUF_MS);
+	}
+
+	ret = ad4695_parse_channel_cfg(indio_dev);
+	if (ret)
+		return ret;
+
+	indio_dev->name = st->chip_info->name;
+	indio_dev->info = &ad4695_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = st->iio_chan;
+	indio_dev->num_channels = st->chip_info->num_voltage_inputs + 1;
+
+	return devm_iio_device_register(dev, indio_dev);
+}
+
+static const struct spi_device_id ad4695_spi_id_table[] = {
+	{ .name = "ad4695", .driver_data = (kernel_ulong_t)&ad4695_chip_info },
+	{ .name = "ad4696", .driver_data = (kernel_ulong_t)&ad4696_chip_info },
+	{ .name = "ad4697", .driver_data = (kernel_ulong_t)&ad4697_chip_info },
+	{ .name = "ad4698", .driver_data = (kernel_ulong_t)&ad4698_chip_info },
+	{ }
+};
+MODULE_DEVICE_TABLE(spi, ad4695_spi_id_table);
+
+static const struct of_device_id ad4695_of_match_table[] = {
+	{ .compatible = "adi,ad4695", .data = &ad4695_chip_info, },
+	{ .compatible = "adi,ad4696", .data = &ad4696_chip_info, },
+	{ .compatible = "adi,ad4697", .data = &ad4697_chip_info, },
+	{ .compatible = "adi,ad4698", .data = &ad4698_chip_info, },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ad4695_of_match_table);
+
+static struct spi_driver ad4695_driver = {
+	.driver = {
+		.name = "ad4695",
+		.of_match_table = ad4695_of_match_table,
+	},
+	.probe = ad4695_probe,
+	.id_table = ad4695_spi_id_table,
+};
+module_spi_driver(ad4695_driver);
+
+MODULE_AUTHOR("Ramona Gradinariu <ramona.gradinariu@analog.com>");
+MODULE_AUTHOR("David Lechner <dlechner@baylibre.com>");
+MODULE_DESCRIPTION("Analog Devices AD4695 ADC driver");
+MODULE_LICENSE("GPL");

-- 
2.45.2

[PATCH v3 3/3] Documentation: iio: Document ad4695 driver

[David Lechner]

The Analog Devices Inc. AD4695 (and similar chips) are complex ADCs that
will benefit from a detailed driver documentation.

This documents the current features supported by the driver.

Signed-off-by: David Lechner <dlechner@baylibre.com>
---

v2 changes:
* Rework DT examples for DT bindings changes

v2 changes:
* Rework DT examples for DT bindings changes
* Fix wrong MAINTAINERS update
---
 Documentation/iio/ad4695.rst | 155 +++++++++++++++++++++++++++++++++++++++++++
 Documentation/iio/index.rst  |   1 +
 MAINTAINERS                  |   1 +
 3 files changed, 157 insertions(+)

diff --git a/Documentation/iio/ad4695.rst b/Documentation/iio/ad4695.rst
new file mode 100644
index 000000000000..a33e573d61d6
--- /dev/null
+++ b/Documentation/iio/ad4695.rst
@@ -0,0 +1,155 @@
+.. SPDX-License-Identifier: GPL-2.0-only
+
+=============
+AD4695 driver
+=============
+
+ADC driver for Analog Devices Inc. AD4695 and similar devices. The module name
+is ``ad4695``.
+
+
+Supported devices
+=================
+
+The following chips are supported by this driver:
+
+* `AD4695 <https://www.analog.com/AD4695>`_
+* `AD4696 <https://www.analog.com/AD4696>`_
+* `AD4697 <https://www.analog.com/AD4697>`_
+* `AD4698 <https://www.analog.com/AD4698>`_
+
+
+Supported features
+==================
+
+SPI wiring modes
+----------------
+
+The driver currently supports the following SPI wiring configuration:
+
+4-wire mode
+^^^^^^^^^^^
+
+In this mode, CNV and CS are tied together and there is a single SDO line.
+
+.. code-block::
+
+    +-------------+         +-------------+
+    |          CS |<-+------| CS          |
+    |         CNV |<-+      |             |
+    |     ADC     |         |     HOST    |
+    |             |         |             |
+    |         SDI |<--------| SDO         |
+    |         SDO |-------->| SDI         |
+    |        SCLK |<--------| SCLK        |
+    +-------------+         +-------------+
+
+To use this mode, in the device tree, omit the ``cnv-gpios`` and
+``spi-rx-bus-width`` properties.
+
+Channel configuration
+---------------------
+
+Since the chip supports multiple ways to configure each channel, this must be
+described in the device tree based on what is actually wired up to the inputs.
+
+There are three typical configurations:
+
+An ``INx`` pin is used as the positive input with the ``REFGND``, ``COM`` or
+the next ``INx`` pin as the negative input.
+
+Pairing with REFGND
+^^^^^^^^^^^^^^^^^^^
+
+Each ``INx`` pin can be used as a pseudo-differential input in conjunction with
+the ``REFGND`` pin. The device tree will look like this:
+
+.. code-block::
+
+    channel@0 {
+        reg = <0>; /* IN0 */
+    };
+
+If no other channel properties are needed (e.g. ``adi,no-high-z``), the channel
+node can be omitted entirely.
+
+This will appear on the IIO bus as the ``voltage0`` channel. The processed value
+(*raw × scale*) will be the voltage present on the ``IN0`` pin relative to
+``REFGND``. (Offset is always 0 when pairing with ``REFGND``.)
+
+Pairing with COM
+^^^^^^^^^^^^^^^^
+
+Each ``INx`` pin can be used as a pseudo-differential input in conjunction with
+the ``COM`` pin. The device tree will look like this:
+
+.. code-block::
+
+    com-supply = <&vref_div_2>;
+
+    channel@1 {
+        reg = <1>; /* IN1 */
+        common-mode-channel = <AD4695_COMMON_MODE_COM>;
+        bipolar;
+    };
+
+This will appear on the IIO bus as the ``voltage1`` channel. The processed value
+(*(raw + offset) × scale*) will be the voltage measured on the ``IN1`` pin
+relative to ``REFGND``. (The offset is determined by the ``com-supply`` voltage.)
+
+The macro comes from:
+
+.. code-block::
+
+    #include <dt-bindings/iio/adi,ad4695.h>
+
+Pairing two INx pins
+^^^^^^^^^^^^^^^^^^^^
+
+An even-numbered ``INx`` pin and the following odd-numbered ``INx`` pin can be
+used as a pseudo-differential input. The device tree for using ``IN2`` as the
+positive input and ``IN3`` as the negative input will look like this:
+
+.. code-block::
+
+    in3-supply = <&vref_div_2>;
+
+    channel@2 {
+        reg = <2>; /* IN2 */
+        common-mode-channel = <3>; /* IN3 */
+        bipolar;
+    };
+
+This will appear on the IIO bus as the ``voltage2`` channel. The processed value
+(*(raw + offset) × scale*) will be the voltage measured on the ``IN1`` pin
+relative to ``REFGND``. (Offset is determined by the ``in3-supply`` voltage.)
+
+VCC supply
+----------
+
+The chip supports being powered by an external LDO via the ``VCC`` input or an
+internal LDO via the ``LDO_IN`` input. The driver looks at the device tree to
+determine which is being used. If ``ldo-supply`` is present, then the internal
+LDO is used. If ``vcc-supply`` is present, then the external LDO is used and
+the internal LDO is disabled.
+
+Reference voltage
+-----------------
+
+The chip supports an external reference voltage via the ``REF`` input or an
+internal buffered reference voltage via the ``REFIN`` input. The driver looks
+at the device tree to determine which is being used. If ``ref-supply`` is
+present, then the external reference voltage is used and the internal buffer is
+disabled. If ``refin-supply`` is present, then the internal buffered reference
+voltage is used.
+
+Unimplemented features
+----------------------
+
+- Additional wiring modes
+- Buffered reads
+- Threshold events
+- Oversampling
+- Gain/offset calibration
+- GPIO support
+- CRC support
diff --git a/Documentation/iio/index.rst b/Documentation/iio/index.rst
index 4c13bfa2865c..df69a76bf583 100644
--- a/Documentation/iio/index.rst
+++ b/Documentation/iio/index.rst
@@ -17,6 +17,7 @@ Industrial I/O Kernel Drivers
 .. toctree::
    :maxdepth: 1
 
+   ad4695
    ad7944
    adis16475
    adis16480
diff --git a/MAINTAINERS b/MAINTAINERS
index c52c4b0e69a8..9b6eaccb34f2 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1216,6 +1216,7 @@ L:	linux-iio@vger.kernel.org
 S:	Supported
 W:	https://ez.analog.com/linux-software-drivers
 F:	Documentation/devicetree/bindings/iio/adc/adi,ad4695.yaml
+F:	Documentation/iio/ad4695.rst
 F:	drivers/iio/adc/ad4695.c
 F:	include/dt-bindings/iio/adi,ad4695.h
 

-- 
2.45.2

Re: [PATCH v3 1/3] dt-bindings: iio: adc: add AD4695 and similar ADCs

[Rob Herring (Arm)]

On Mon, 24 Jun 2024 17:01:53 -0500, David Lechner wrote:
> Add device tree bindings for AD4695 and similar ADCs.
> 
> Signed-off-by: David Lechner <dlechner@baylibre.com>
> ---
> 
> Note, this may trigger a DT build warning "common-mode-channel: missing
> type definition" if the builder doesn't include the recently added
> common-mode-channel property [1]. This should be safe to ignore (passes
> make dt_binding_check locally).
> 
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git/commit/?h=testing&id=d86deaec1c5b0fb60c3619e8d2ae7a1d722fd2ad
> 
> v3 changes:
> * Change interrupts to be per pin instead of per signal.
> * Drop diff-channels and single-channel properties.
> * Odd numbered pins added to common-mode-channel property enum.
> * REFGND and COM values changes to avoid confusion with pin numbers.
> * Add inX-supply properties for odd numbed input pins.
> 
> v2 changes:
> * Drop *-wlcsp compatible strings
> * Don't use fallback compatible strings
> * Reword supply descriptions
> * Use standard channel properties instead of adi,pin-pairing
> * Fix unnecessary | character
> * Fix missing blank line
> * Add header file with common mode channel macros
> ---
>  .../devicetree/bindings/iio/adc/adi,ad4695.yaml    | 256 +++++++++++++++++++++
>  MAINTAINERS                                        |  10 +
>  include/dt-bindings/iio/adi,ad4695.h               |   9 +
>  3 files changed, 275 insertions(+)
> 

My bot found errors running 'make dt_binding_check' on your patch:

yamllint warnings/errors:

dtschema/dtc warnings/errors:
/builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/iio/adc/adi,ad4695.yaml: common-mode-channel: missing type definition

doc reference errors (make refcheckdocs):

See https://patchwork.ozlabs.org/project/devicetree-bindings/patch/20240624-iio-adc-ad4695-v3-1-a22c302f06bf@baylibre.com

The base for the series is generally the latest rc1. A different dependency
should be noted in *this* patch.

If you already ran 'make dt_binding_check' and didn't see the above
error(s), then make sure 'yamllint' is installed and dt-schema is up to
date:

pip3 install dtschema --upgrade

Please check and re-submit after running the above command yourself. Note
that DT_SCHEMA_FILES can be set to your schema file to speed up checking
your schema. However, it must be unset to test all examples with your schema.

Re: [PATCH v3 1/3] dt-bindings: iio: adc: add AD4695 and similar ADCs

[Conor Dooley]

[-- Attachment #1: Type: text/plain, Size: 505 bytes --]

On Mon, Jun 24, 2024 at 05:01:53PM -0500, David Lechner wrote:
> Add device tree bindings for AD4695 and similar ADCs.
> 
> Signed-off-by: David Lechner <dlechner@baylibre.com>
> ---
> 
> Note, this may trigger a DT build warning "common-mode-channel: missing
> type definition" if the builder doesn't include the recently added
> common-mode-channel property [1]. This should be safe to ignore (passes
> make dt_binding_check locally).

Reviewed-by: Conor Dooley <conor.dooley@microchip.com>

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 228 bytes --]

Re: [PATCH v3 2/3] iio: adc: ad4695: Add driver for AD4695 and similar ADCs

[Nuno Sá]

Hi David,

minor stuff from me..

On Mon, 2024-06-24 at 17:01 -0500, David Lechner wrote:
> This is a new driver for Analog Devices Inc. AD4695 and similar ADCs.
> The initial driver supports initializing the chip including configuring
> all possible LDO and reference voltage sources as well as any possible
> voltage input channel wiring configuration.
> 
> Only the 4-wire SPI wiring mode where the CNV pin is tied to the CS pin
> is supported at this time. And reading sample data from the ADC can only
> be done in direct mode for now.
> 
> Co-developed-by: Ramona Gradinariu <ramona.gradinariu@analog.com>
> Signed-off-by: Ramona Gradinariu <ramona.gradinariu@analog.com>
> Signed-off-by: David Lechner <dlechner@baylibre.com>
> ---
> 
> v3 changes:
> * always include all channels, not just ones customized in DT
> * rework channel fwnode parsing for DT changes
> 
> v2 changes:
> * rework register definition macros
> * remove code structure comments at top level
> * remove simple wrapper functions around regmap functions
> * rework channel fwnode parsing for DT changes
> * fix missing return value check
> ---
>  MAINTAINERS              |   1 +
>  drivers/iio/adc/Kconfig  |  11 +
>  drivers/iio/adc/Makefile |   1 +
>  drivers/iio/adc/ad4695.c | 730
> +++++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 743 insertions(+)
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 025ee138a713..c52c4b0e69a8 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -1216,6 +1216,7 @@ L:	linux-iio@vger.kernel.org
>  S:	Supported
>  W:	https://ez.analog.com/linux-software-drivers
>  F:	Documentation/devicetree/bindings/iio/adc/adi,ad4695.yaml
> +F:	drivers/iio/adc/ad4695.c
>  F:	include/dt-bindings/iio/adi,ad4695.h
>  
>  ANALOG DEVICES INC AD7091R DRIVER
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index b8184706c7d1..eed5547a5078 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -36,6 +36,17 @@ config AD4130
>  	  To compile this driver as a module, choose M here: the module will
> be
>  	  called ad4130.
>  
> +config AD4695
> +	tristate "Analog Device AD4695 ADC Driver"
> +	depends on SPI
> +	select REGMAP_SPI
> +	help
> +	  Say yes here to build support for Analog Devices AD4695 and similar
> +	  analog to digital converters (ADC).
> +
> +	  To compile this driver as a module, choose M here: the module will
> be
> +	  called ad4695.
> +
>  config AD7091R
>  	tristate
>  
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index 51298c52b223..c180c85b6327 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -7,6 +7,7 @@
>  obj-$(CONFIG_AB8500_GPADC) += ab8500-gpadc.o
>  obj-$(CONFIG_AD_SIGMA_DELTA) += ad_sigma_delta.o
>  obj-$(CONFIG_AD4130) += ad4130.o
> +obj-$(CONFIG_AD4695) += ad4695.o
>  obj-$(CONFIG_AD7091R) += ad7091r-base.o
>  obj-$(CONFIG_AD7091R5) += ad7091r5.o
>  obj-$(CONFIG_AD7091R8) += ad7091r8.o
> diff --git a/drivers/iio/adc/ad4695.c b/drivers/iio/adc/ad4695.c
> new file mode 100644
> index 000000000000..72ab5b997f6e
> --- /dev/null
> +++ b/drivers/iio/adc/ad4695.c
> @@ -0,0 +1,730 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * SPI ADC driver for Analog Devices Inc. AD4695 and similar chips
> + *
> + * https://www.analog.com/en/products/ad4695.html
> + * https://www.analog.com/en/products/ad4696.html
> + * https://www.analog.com/en/products/ad4697.html
> + * https://www.analog.com/en/products/ad4698.html
> + *
> + * Copyright 2024 Analog Devices Inc.
> + * Copyright 2024 BayLibre, SAS
> + */
> +
> +#include <dt-bindings/iio/adi,ad4695.h>
> +#include <linux/bitfield.h>
> +#include <linux/bits.h>
> +#include <linux/compiler.h>
> +#include <linux/delay.h>
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/iio/iio.h>
> +#include <linux/property.h>
> +#include <linux/regmap.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/spi/spi.h>
> +#include <linux/units.h>
> +
> 

...

> +
> +static int ad4695_write_chn_cfg(struct ad4695_state *st,
> +				struct ad4695_channel_config *cfg)
> +{
> +	u32 mask = 0, val = 0;
> +
> +	mask |= AD4695_REG_CONFIG_IN_MODE;
> +	val |= FIELD_PREP(AD4695_REG_CONFIG_IN_MODE, cfg->bipolar ? 1 : 0);
> +

nit: don't need to OR the first assignments and so initializing the variables.

> +	mask |= AD4695_REG_CONFIG_IN_PAIR;
> +	val |= FIELD_PREP(AD4695_REG_CONFIG_IN_PAIR, cfg->pin_pairing);
> +
> +	mask |= AD4695_REG_CONFIG_IN_AINHIGHZ_EN;
> +	val |= FIELD_PREP(AD4695_REG_CONFIG_IN_AINHIGHZ_EN, cfg->highz_en ? 1
> : 0);
> +
> +	return regmap_update_bits(st->regmap, AD4695_REG_CONFIG_IN(cfg-
> >channel),
> +				  mask, val);
> +}
> +
> +/**
> + * ad4695_read_one_sample - Read a single sample using single-cycle mode
> + * @st: The AD4695 state
> + * @address: The address of the channel to read
> + *
> + * Upon return, the sample will be stored in the raw_data field of @st.
> + *
> + * Context: can sleep, must be called with iio_device_claim_direct held
> + * Return: 0 on success, a negative error code on failure
> + */
> +static int ad4695_read_one_sample(struct ad4695_state *st, unsigned int
> address)
> +{
> +	struct spi_transfer xfer[2] = { };
> +	int ret;
> +
> +	ret = ad4695_set_single_cycle_mode(st, address);
> +	if (ret)
> +		return ret;
> +
> +	/*
> +	 * Setting the first channel to the temperature channel isn't
> supported
> +	 * in single-cycle mode, so we have to do an extra xfer to read the
> +	 * temperature.
> +	 */
> +	if (address == AD4695_CMD_TEMP_CHAN) {
> +		/* We aren't reading, so we can make this a short xfer. */
> +		st->cnv_cmd2 = AD4695_CMD_TEMP_CHAN << 3;
> +		xfer[0].bits_per_word = 8;

nit: isn't this the default?

> +		xfer[0].tx_buf = &st->cnv_cmd2;
> +		xfer[0].len = 1;
> +		xfer[0].cs_change = 1;
> +		xfer[0].cs_change_delay.value = AD4695_T_CONVERT_NS;
> +		xfer[0].cs_change_delay.unit = SPI_DELAY_UNIT_NSECS;
> +
> +		/* Then read the result and exit conversion mode. */
> +		st->cnv_cmd = AD4695_CMD_EXIT_CNV_MODE << 11;
> +		xfer[1].bits_per_word = 16;
> +		xfer[1].tx_buf = &st->cnv_cmd;
> +		xfer[1].rx_buf = &st->raw_data;
> +		xfer[1].len = 2;
> +
> +		return spi_sync_transfer(st->spi, xfer, 2);
> +	}
> +
> +	/*
> +	 * The conversion has already been done and we just have to read the
> +	 * result and exit conversion mode.
> +	 */
> +	st->cnv_cmd = AD4695_CMD_EXIT_CNV_MODE << 11;
> +	xfer[0].bits_per_word = 16;
> +	xfer[0].tx_buf = &st->cnv_cmd;
> +	xfer[0].rx_buf = &st->raw_data;
> +	xfer[0].len = 2;
> +
> +	return spi_sync_transfer(st->spi, xfer, 1);
> +}
> +
> +static int ad4695_read_raw(struct iio_dev *indio_dev,
> +			   struct iio_chan_spec const *chan,
> +			   int *val, int *val2, long mask)
> +{
> +	struct ad4695_state *st = iio_priv(indio_dev);
> +	struct ad4695_channel_config *cfg = &st->channels_cfg[chan-
> >scan_index];
> +	u8 realbits = chan->scan_type.realbits;
> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		iio_device_claim_direct_scoped(return -EBUSY, indio_dev) {
> +			ret = ad4695_read_one_sample(st, chan->address);
> +			if (ret)
> +				return ret;
> +
> +			if (chan->scan_type.sign == 's')
> +				*val = sign_extend32(st->raw_data, realbits -
> 1);
> +			else
> +				*val = st->raw_data;
> +
> +			return IIO_VAL_INT;
> +		}
> +		unreachable();
> +	case IIO_CHAN_INFO_SCALE:
> +		switch (chan->type) {
> +		case IIO_VOLTAGE:
> +			*val = st->vref_mv;
> +			*val2 = chan->scan_type.realbits;
> +			return IIO_VAL_FRACTIONAL_LOG2;
> +		case IIO_TEMP:
> +			/* T_scale (°C) = raw * V_REF (mV) / (-1.8 mV/°C *
> 2^16) */
> +			*val = st->vref_mv * -556;
> +			*val2 = 16;
> +			return IIO_VAL_FRACTIONAL_LOG2;
> +		default:
> +			return -EINVAL;
> +		}
> +	case IIO_CHAN_INFO_OFFSET:
> +		switch (chan->type) {
> +		case IIO_VOLTAGE:
> +			if (cfg->pin_pairing == AD4695_IN_PAIR_COM)
> +				*val = st->com_mv * (1 << realbits) / st-
> >vref_mv;
> +			else if (cfg->pin_pairing == AD4695_IN_PAIR_EVEN_ODD)
> +				*val = cfg->common_mode_mv * (1 << realbits)
> / st->vref_mv;
> +			else
> +				*val = 0;
> +
> +			return IIO_VAL_INT;
> +		case IIO_TEMP:
> +			/* T_offset (°C) = -725 mV / (-1.8 mV/°C) */
> +			/* T_offset (raw) = T_offset (°C) * (-1.8 mV/°C) *
> 2^16 / V_REF (mV) */
> +			*val = -47513600;
> +			*val2 = st->vref_mv;
> +			return IIO_VAL_FRACTIONAL;
> +		default:
> +			return -EINVAL;
> +		}
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int ad4695_debugfs_reg_access(struct iio_dev *indio_dev, unsigned int
> reg,
> +				     unsigned int writeval, unsigned int
> *readval)
> +{
> +	struct ad4695_state *st = iio_priv(indio_dev);
> +
> +	iio_device_claim_direct_scoped(return -EBUSY, indio_dev) {
> +		if (readval)
> +			return regmap_read(st->regmap, reg, readval);
> +
> +		return regmap_write(st->regmap, reg, writeval);
> +	}
> +
> +	unreachable();
> +}
> +
> +static const struct iio_info ad4695_info = {
> +	.read_raw = &ad4695_read_raw,
> +	.debugfs_reg_access = &ad4695_debugfs_reg_access,
> +};
> +
> +static int ad4695_parse_channel_cfg(struct iio_dev *indio_dev)
> +{
> +	struct device *dev = indio_dev->dev.parent;
> +	struct ad4695_state *st = iio_priv(indio_dev);

Why not passing in struct ad4695_state directly?

...

> 
> +
> +	/* Needed for debugfs since it only access registers 1 byte at a
> time. */
> +	ret = regmap_set_bits(st->regmap, AD4695_REG_SPI_CONFIG_C,
> +			      AD4695_REG_SPI_CONFIG_C_MB_STRICT);
> +	if (ret)
> +		return ret;
> +

Question... do we gain something but not doing the above? Because debugfs is
optional and always doing it even when it's not present looks unnecessary. 

- Nuno Sá

Re: [PATCH v3 2/3] iio: adc: ad4695: Add driver for AD4695 and similar ADCs

[David Lechner]

On 6/26/24 6:47 AM, Nuno Sá wrote:
> Hi David,
> 
> minor stuff from me..
> 
> 
> ...
> 
>> +
>> +static int ad4695_write_chn_cfg(struct ad4695_state *st,
>> +				struct ad4695_channel_config *cfg)
>> +{
>> +	u32 mask = 0, val = 0;
>> +
>> +	mask |= AD4695_REG_CONFIG_IN_MODE;
>> +	val |= FIELD_PREP(AD4695_REG_CONFIG_IN_MODE, cfg->bipolar ? 1 : 0);
>> +
> 
> nit: don't need to OR the first assignments and so initializing the variables.

:+1:

> 
>> +	mask |= AD4695_REG_CONFIG_IN_PAIR;
>> +	val |= FIELD_PREP(AD4695_REG_CONFIG_IN_PAIR, cfg->pin_pairing);
>> +
>> +	mask |= AD4695_REG_CONFIG_IN_AINHIGHZ_EN;
>> +	val |= FIELD_PREP(AD4695_REG_CONFIG_IN_AINHIGHZ_EN, cfg->highz_en ? 1
>> : 0);
>> +
>> +	return regmap_update_bits(st->regmap, AD4695_REG_CONFIG_IN(cfg-
>>> channel),
>> +				  mask, val);
>> +}
>> +
>> +/**
>> + * ad4695_read_one_sample - Read a single sample using single-cycle mode
>> + * @st: The AD4695 state
>> + * @address: The address of the channel to read
>> + *
>> + * Upon return, the sample will be stored in the raw_data field of @st.
>> + *
>> + * Context: can sleep, must be called with iio_device_claim_direct held
>> + * Return: 0 on success, a negative error code on failure
>> + */
>> +static int ad4695_read_one_sample(struct ad4695_state *st, unsigned int
>> address)
>> +{
>> +	struct spi_transfer xfer[2] = { };
>> +	int ret;
>> +
>> +	ret = ad4695_set_single_cycle_mode(st, address);
>> +	if (ret)
>> +		return ret;
>> +
>> +	/*
>> +	 * Setting the first channel to the temperature channel isn't
>> supported
>> +	 * in single-cycle mode, so we have to do an extra xfer to read the
>> +	 * temperature.
>> +	 */
>> +	if (address == AD4695_CMD_TEMP_CHAN) {
>> +		/* We aren't reading, so we can make this a short xfer. */
>> +		st->cnv_cmd2 = AD4695_CMD_TEMP_CHAN << 3;
>> +		xfer[0].bits_per_word = 8;
> 
> nit: isn't this the default?

yes (looks like leftover from testing when I was trying 16 instead of 8)

> 
>> +		xfer[0].tx_buf = &st->cnv_cmd2;
>> +		xfer[0].len = 1;
>> +		xfer[0].cs_change = 1;
>> +		xfer[0].cs_change_delay.value = AD4695_T_CONVERT_NS;
>> +		xfer[0].cs_change_delay.unit = SPI_DELAY_UNIT_NSECS;
>> +
>> +		/* Then read the result and exit conversion mode. */
>> +		st->cnv_cmd = AD4695_CMD_EXIT_CNV_MODE << 11;
>> +		xfer[1].bits_per_word = 16;
>> +		xfer[1].tx_buf = &st->cnv_cmd;
>> +		xfer[1].rx_buf = &st->raw_data;
>> +		xfer[1].len = 2;
>> +
>> +		return spi_sync_transfer(st->spi, xfer, 2);
>> +	}
>> +

...

>> +
>> +static int ad4695_parse_channel_cfg(struct iio_dev *indio_dev)
>> +{
>> +	struct device *dev = indio_dev->dev.parent;
>> +	struct ad4695_state *st = iio_priv(indio_dev);
> 
> Why not passing in struct ad4695_state directly?

Probably because that is how it was done in the ADI tree driver
I started with. Changing it to two parameters would be fine.

> 
> ...
> 
>>
>> +
>> +	/* Needed for debugfs since it only access registers 1 byte at a
>> time. */
>> +	ret = regmap_set_bits(st->regmap, AD4695_REG_SPI_CONFIG_C,
>> +			      AD4695_REG_SPI_CONFIG_C_MB_STRICT);
>> +	if (ret)
>> +		return ret;
>> +
> 
> Question... do we gain something but not doing the above? Because debugfs is
> optional and always doing it even when it's not present looks unnecessary. 

I haven't got to a place where we need to read or write a 2 byte register
yet, so I'm not sure. My plan is to defer worrying about it until then
and update this if necessary in a future patch when it actually makes a
difference. But for now, this is harmless because we are only reading
and writing single byte registers.

> 
> - Nuno Sá
> 

Re: [PATCH v3 2/3] iio: adc: ad4695: Add driver for AD4695 and similar ADCs

[Nuno Sá]

On Wed, 2024-06-26 at 09:42 -0500, David Lechner wrote:
> On 6/26/24 6:47 AM, Nuno Sá wrote:
> > Hi David,
> > 
> > minor stuff from me..
> > 
> > 
> > ...
> > 
> > > +
> > > +static int ad4695_write_chn_cfg(struct ad4695_state *st,
> > > +				struct ad4695_channel_config *cfg)
> > > +{
> > > +	u32 mask = 0, val = 0;
> > > +
> > > +	mask |= AD4695_REG_CONFIG_IN_MODE;
> > > +	val |= FIELD_PREP(AD4695_REG_CONFIG_IN_MODE, cfg->bipolar ? 1 :
> > > 0);
> > > +
> > 
> > nit: don't need to OR the first assignments and so initializing the
> > variables.
> 
> :+1:
> 
> > 
> > > +	mask |= AD4695_REG_CONFIG_IN_PAIR;
> > > +	val |= FIELD_PREP(AD4695_REG_CONFIG_IN_PAIR, cfg->pin_pairing);
> > > +
> > > +	mask |= AD4695_REG_CONFIG_IN_AINHIGHZ_EN;
> > > +	val |= FIELD_PREP(AD4695_REG_CONFIG_IN_AINHIGHZ_EN, cfg->highz_en
> > > ? 1
> > > : 0);
> > > +
> > > +	return regmap_update_bits(st->regmap, AD4695_REG_CONFIG_IN(cfg-
> > > > channel),
> > > +				  mask, val);
> > > +}
> > > +
> > > +/**
> > > + * ad4695_read_one_sample - Read a single sample using single-cycle mode
> > > + * @st: The AD4695 state
> > > + * @address: The address of the channel to read
> > > + *
> > > + * Upon return, the sample will be stored in the raw_data field of @st.
> > > + *
> > > + * Context: can sleep, must be called with iio_device_claim_direct held
> > > + * Return: 0 on success, a negative error code on failure
> > > + */
> > > +static int ad4695_read_one_sample(struct ad4695_state *st, unsigned int
> > > address)
> > > +{
> > > +	struct spi_transfer xfer[2] = { };
> > > +	int ret;
> > > +
> > > +	ret = ad4695_set_single_cycle_mode(st, address);
> > > +	if (ret)
> > > +		return ret;
> > > +
> > > +	/*
> > > +	 * Setting the first channel to the temperature channel isn't
> > > supported
> > > +	 * in single-cycle mode, so we have to do an extra xfer to read
> > > the
> > > +	 * temperature.
> > > +	 */
> > > +	if (address == AD4695_CMD_TEMP_CHAN) {
> > > +		/* We aren't reading, so we can make this a short xfer.
> > > */
> > > +		st->cnv_cmd2 = AD4695_CMD_TEMP_CHAN << 3;
> > > +		xfer[0].bits_per_word = 8;
> > 
> > nit: isn't this the default?
> 
> yes (looks like leftover from testing when I was trying 16 instead of 8)
> 
> > 
> > > +		xfer[0].tx_buf = &st->cnv_cmd2;
> > > +		xfer[0].len = 1;
> > > +		xfer[0].cs_change = 1;
> > > +		xfer[0].cs_change_delay.value = AD4695_T_CONVERT_NS;
> > > +		xfer[0].cs_change_delay.unit = SPI_DELAY_UNIT_NSECS;
> > > +
> > > +		/* Then read the result and exit conversion mode. */
> > > +		st->cnv_cmd = AD4695_CMD_EXIT_CNV_MODE << 11;
> > > +		xfer[1].bits_per_word = 16;
> > > +		xfer[1].tx_buf = &st->cnv_cmd;
> > > +		xfer[1].rx_buf = &st->raw_data;
> > > +		xfer[1].len = 2;
> > > +
> > > +		return spi_sync_transfer(st->spi, xfer, 2);
> > > +	}
> > > +
> 
> ...
> 
> > > +
> > > +static int ad4695_parse_channel_cfg(struct iio_dev *indio_dev)
> > > +{
> > > +	struct device *dev = indio_dev->dev.parent;
> > > +	struct ad4695_state *st = iio_priv(indio_dev);
> > 
> > Why not passing in struct ad4695_state directly?
> 
> Probably because that is how it was done in the ADI tree driver
> I started with. Changing it to two parameters would be fine.
> 

I think you're fine in just passing ad4695_state. If I'm not missing nothing the
iio_dev is only to get the parent device and you have that in st->spi.

> > 
> > ...
> > 
> > > 
> > > +
> > > +	/* Needed for debugfs since it only access registers 1 byte at a
> > > time. */
> > > +	ret = regmap_set_bits(st->regmap, AD4695_REG_SPI_CONFIG_C,
> > > +			      AD4695_REG_SPI_CONFIG_C_MB_STRICT);
> > > +	if (ret)
> > > +		return ret;
> > > +
> > 
> > Question... do we gain something but not doing the above? Because debugfs is
> > optional and always doing it even when it's not present looks unnecessary. 
> 
> I haven't got to a place where we need to read or write a 2 byte register
> yet, so I'm not sure. My plan is to defer worrying about it until then
> and update this if necessary in a future patch when it actually makes a
> difference. But for now, this is harmless because we are only reading
> and writing single byte registers.
> 

ack

- Nuno Sá
> 

Re: [PATCH v3 2/3] iio: adc: ad4695: Add driver for AD4695 and similar ADCs

[Jonathan Cameron]

On Mon, 24 Jun 2024 17:01:54 -0500
David Lechner <dlechner@baylibre.com> wrote:

> This is a new driver for Analog Devices Inc. AD4695 and similar ADCs.
> The initial driver supports initializing the chip including configuring
> all possible LDO and reference voltage sources as well as any possible
> voltage input channel wiring configuration.
> 
> Only the 4-wire SPI wiring mode where the CNV pin is tied to the CS pin
> is supported at this time. And reading sample data from the ADC can only
> be done in direct mode for now.
> 
> Co-developed-by: Ramona Gradinariu <ramona.gradinariu@analog.com>
> Signed-off-by: Ramona Gradinariu <ramona.gradinariu@analog.com>
> Signed-off-by: David Lechner <dlechner@baylibre.com>

Some minor bits an pieces from me.

> diff --git a/drivers/iio/adc/ad4695.c b/drivers/iio/adc/ad4695.c
> new file mode 100644
> index 000000000000..72ab5b997f6e
> --- /dev/null
> +++ b/drivers/iio/adc/ad4695.c
> @@ -0,0 +1,730 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * SPI ADC driver for Analog Devices Inc. AD4695 and similar chips
> + *
> + * https://www.analog.com/en/products/ad4695.html
> + * https://www.analog.com/en/products/ad4696.html
> + * https://www.analog.com/en/products/ad4697.html
> + * https://www.analog.com/en/products/ad4698.html
> + *
> + * Copyright 2024 Analog Devices Inc.
> + * Copyright 2024 BayLibre, SAS
> + */
> +
> +#include <dt-bindings/iio/adi,ad4695.h>

Stick driver specific includes after linux ones.
Probably a blank line in between as well.

> +#include <linux/bitfield.h>
> +#include <linux/bits.h>
> +#include <linux/compiler.h>
> +#include <linux/delay.h>
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/iio/iio.h>
> +#include <linux/property.h>
> +#include <linux/regmap.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/spi/spi.h>
> +#include <linux/units.h>
> +

> +
> +/**
> + * ad4695_read_one_sample - Read a single sample using single-cycle mode
> + * @st: The AD4695 state
> + * @address: The address of the channel to read
> + *
> + * Upon return, the sample will be stored in the raw_data field of @st.
> + *
> + * Context: can sleep, must be called with iio_device_claim_direct held
> + * Return: 0 on success, a negative error code on failure
> + */
> +static int ad4695_read_one_sample(struct ad4695_state *st, unsigned int address)
> +{
> +	struct spi_transfer xfer[2] = { };
> +	int ret;
> +
> +	ret = ad4695_set_single_cycle_mode(st, address);
> +	if (ret)
> +		return ret;
> +
> +	/*
> +	 * Setting the first channel to the temperature channel isn't supported
> +	 * in single-cycle mode, so we have to do an extra xfer to read the
> +	 * temperature.
> +	 */
> +	if (address == AD4695_CMD_TEMP_CHAN) {
> +		/* We aren't reading, so we can make this a short xfer. */
I'd be tempted to let the compiler figure out it can combine storage for xfer and
do something like
		struct spi_transfer xfer[2] = {
			{
				.bits_per_word = 8,
				.tx_buf = ...

			}, {
			},
		};

		st->cnv_cmd2 = ...
etc

Advantage is that it is clearly structured data.   Up to you though to
decide if this is worth doing. I don't care that much!


> +		st->cnv_cmd2 = AD4695_CMD_TEMP_CHAN << 3;
> +		xfer[0].bits_per_word = 8;
> +		xfer[0].tx_buf = &st->cnv_cmd2;
> +		xfer[0].len = 1;
> +		xfer[0].cs_change = 1;
> +		xfer[0].cs_change_delay.value = AD4695_T_CONVERT_NS;
> +		xfer[0].cs_change_delay.unit = SPI_DELAY_UNIT_NSECS;
> +
> +		/* Then read the result and exit conversion mode. */
> +		st->cnv_cmd = AD4695_CMD_EXIT_CNV_MODE << 11;
> +		xfer[1].bits_per_word = 16;
> +		xfer[1].tx_buf = &st->cnv_cmd;
> +		xfer[1].rx_buf = &st->raw_data;
> +		xfer[1].len = 2;
> +
> +		return spi_sync_transfer(st->spi, xfer, 2);
> +	}

then an else here to reduce the scope of another xfer structure.

> +
> +	/*
> +	 * The conversion has already been done and we just have to read the
> +	 * result and exit conversion mode.
> +	 */
> +	st->cnv_cmd = AD4695_CMD_EXIT_CNV_MODE << 11;
> +	xfer[0].bits_per_word = 16;
> +	xfer[0].tx_buf = &st->cnv_cmd;
> +	xfer[0].rx_buf = &st->raw_data;
> +	xfer[0].len = 2;
> +
> +	return spi_sync_transfer(st->spi, xfer, 1);
> +}

Re: [PATCH v3 2/3] iio: adc: ad4695: Add driver for AD4695 and similar ADCs

[David Lechner]

On 6/29/24 2:20 PM, Jonathan Cameron wrote:
> On Mon, 24 Jun 2024 17:01:54 -0500
> David Lechner <dlechner@baylibre.com> wrote:
> 

...

>> +
>> +/**
>> + * ad4695_read_one_sample - Read a single sample using single-cycle mode
>> + * @st: The AD4695 state
>> + * @address: The address of the channel to read
>> + *
>> + * Upon return, the sample will be stored in the raw_data field of @st.
>> + *
>> + * Context: can sleep, must be called with iio_device_claim_direct held
>> + * Return: 0 on success, a negative error code on failure
>> + */
>> +static int ad4695_read_one_sample(struct ad4695_state *st, unsigned int address)
>> +{
>> +	struct spi_transfer xfer[2] = { };
>> +	int ret;
>> +
>> +	ret = ad4695_set_single_cycle_mode(st, address);
>> +	if (ret)
>> +		return ret;
>> +
>> +	/*
>> +	 * Setting the first channel to the temperature channel isn't supported
>> +	 * in single-cycle mode, so we have to do an extra xfer to read the
>> +	 * temperature.
>> +	 */
>> +	if (address == AD4695_CMD_TEMP_CHAN) {
>> +		/* We aren't reading, so we can make this a short xfer. */
> I'd be tempted to let the compiler figure out it can combine storage for xfer and
> do something like
> 		struct spi_transfer xfer[2] = {
> 			{
> 				.bits_per_word = 8,
> 				.tx_buf = ...
> 
> 			}, {
> 			},
> 		};
> 
> 		st->cnv_cmd2 = ...
> etc
> 
> Advantage is that it is clearly structured data.   Up to you though to
> decide if this is worth doing. I don't care that much!
> 
> 
>> +		st->cnv_cmd2 = AD4695_CMD_TEMP_CHAN << 3;
>> +		xfer[0].bits_per_word = 8;
>> +		xfer[0].tx_buf = &st->cnv_cmd2;
>> +		xfer[0].len = 1;
>> +		xfer[0].cs_change = 1;
>> +		xfer[0].cs_change_delay.value = AD4695_T_CONVERT_NS;
>> +		xfer[0].cs_change_delay.unit = SPI_DELAY_UNIT_NSECS;
>> +
>> +		/* Then read the result and exit conversion mode. */
>> +		st->cnv_cmd = AD4695_CMD_EXIT_CNV_MODE << 11;
>> +		xfer[1].bits_per_word = 16;
>> +		xfer[1].tx_buf = &st->cnv_cmd;
>> +		xfer[1].rx_buf = &st->raw_data;
>> +		xfer[1].len = 2;
>> +
>> +		return spi_sync_transfer(st->spi, xfer, 2);
>> +	}
> 
> then an else here to reduce the scope of another xfer structure.

Tempting, but then I risk the complaint of else after return. :-)

I also realized that the second xfer above is the same as the one
below, so could skip the return here and avoid some duplicated code
(just need to add an index variable instead of hard-coding xfer[0]).

> 
>> +
>> +	/*
>> +	 * The conversion has already been done and we just have to read the
>> +	 * result and exit conversion mode.
>> +	 */
>> +	st->cnv_cmd = AD4695_CMD_EXIT_CNV_MODE << 11;
>> +	xfer[0].bits_per_word = 16;
>> +	xfer[0].tx_buf = &st->cnv_cmd;
>> +	xfer[0].rx_buf = &st->raw_data;
>> +	xfer[0].len = 2;
>> +
>> +	return spi_sync_transfer(st->spi, xfer, 1);
>> +}