[PATCH v3 0/2] Add max14001 support

[PATCH v3 0/2] Add max14001 support

[Kim Seer Paller]

Hi all,

Attached link is the app note I used as reference for programming the max14001,
which I found to provide a much easier approach. You can find it here:
https://www.analog.com/media/en/technical-documentation/user-guides/guide-to-programming-the-max14001max14002-isolated-adcs--maxim-integrated.pdf

The code has been tested and is working fine with the max14001pmb and
max14001evsys boards on the Raspberry Pi 4.

Changes in v3:

max14001:
 * Replaced __cacheline_aligned with __aligned(IIO_DMA_MINALIGN).
 * Removed redundant assignment of the tx variable in the max14001_write()
 and max14001_read() functions.
 * Assigned struct device *dev with &spi->dev to improve code readability.
 * Utilized a non-regmap approach and ensure a consistent use of interface
 throughout the driver code. I attempted to use the regmap API but faced
 difficulties in implementing it due to the timing diagram requirements.
 Specifically, the need to change the chip select between transfers, which, as
 far as I know, is not applicable with regmap. While I am open to thorough
 guidance and suggestions on utilizing the regmap API, for now, I have chosen
 to stick with the non-regmap approach.

bindings:
 * Utilized the default register values, which led to the omission of some
 properties in v2. I plan to include and switch to generic values the excluded
 properties in v1 in future support.
 * Dropped the status property.
 * Moved the allOf property after the required property for better alignment.

Best Regards,
Kim Seer Paller

Kim Seer Paller (2):
  dt-bindings:iio:adc: add max14001
  iio: adc: max14001: New driver

 .../bindings/iio/adc/adi,max14001.yaml        |  54 +++
 MAINTAINERS                                   |   8 +
 drivers/iio/adc/Kconfig                       |  10 +
 drivers/iio/adc/Makefile                      |   1 +
 drivers/iio/adc/max14001.c                    | 337 ++++++++++++++++++
 5 files changed, 410 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/adi,max14001.yaml
 create mode 100644 drivers/iio/adc/max14001.c


base-commit: 9561de3a55bed6bdd44a12820ba81ec416e705a7
-- 
2.34.1

[PATCH v3 1/2] dt-bindings:iio:adc: add max14001

[Kim Seer Paller]

The MAX14001 is configurable, isolated 10-bit ADCs for multi-range
binary inputs.

Signed-off-by: Kim Seer Paller <kimseer.paller@analog.com>
---
 .../bindings/iio/adc/adi,max14001.yaml        | 54 +++++++++++++++++++
 MAINTAINERS                                   |  7 +++
 2 files changed, 61 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/adi,max14001.yaml

diff --git a/Documentation/devicetree/bindings/iio/adc/adi,max14001.yaml b/Documentation/devicetree/bindings/iio/adc/adi,max14001.yaml
new file mode 100644
index 000000000000..9d03c611fca3
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/adc/adi,max14001.yaml
@@ -0,0 +1,54 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+# Copyright 2023 Analog Devices Inc.
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/adc/adi,max14001.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Analog Devices MAX14001 ADC
+
+maintainers:
+  - Kim Seer Paller <kimseer.paller@analog.com>
+
+description: |
+    Single channel 10 bit ADC with SPI interface. Datasheet
+    can be found here:
+      https://www.analog.com/media/en/technical-documentation/data-sheets/MAX14001-MAX14002.pdf
+
+properties:
+  compatible:
+    enum:
+      - adi,max14001
+
+  reg:
+    maxItems: 1
+
+  spi-max-frequency:
+    maximum: 5000000
+
+  vref-supply:
+    description: Voltage reference to establish input scaling.
+
+required:
+  - compatible
+  - reg
+
+allOf:
+  - $ref: /schemas/spi/spi-peripheral-props.yaml#
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        adc@0 {
+            compatible = "adi,max14001";
+            reg = <0>;
+            spi-max-frequency = <5000000>;
+            vref-supply = <&vref_reg>;
+        };
+    };
+...
diff --git a/MAINTAINERS b/MAINTAINERS
index 0dab9737ec16..b8ad615d011f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12660,6 +12660,13 @@ S:	Maintained
 F:	Documentation/devicetree/bindings/sound/max9860.txt
 F:	sound/soc/codecs/max9860.*
 
+MAX14001 IIO ADC DRIVER
+M:	Kim Seer Paller <kimseer.paller@analog.com>
+L:	linux-iio@vger.kernel.org
+S:	Supported
+W:	https://ez.analog.com/linux-software-drivers
+F:	Documentation/devicetree/bindings/iio/dac/adi,max14001.yaml
+
 MAXBOTIX ULTRASONIC RANGER IIO DRIVER
 M:	Andreas Klinger <ak@it-klinger.de>
 L:	linux-iio@vger.kernel.org
-- 
2.34.1

[PATCH v3 2/2] iio: adc: max14001: New driver

[Kim Seer Paller]

The MAX14001 is configurable, isolated 10-bit ADCs for multi-range
binary inputs.

Signed-off-by: Kim Seer Paller <kimseer.paller@analog.com>
---
 MAINTAINERS                |   1 +
 drivers/iio/adc/Kconfig    |  10 ++
 drivers/iio/adc/Makefile   |   1 +
 drivers/iio/adc/max14001.c | 337 +++++++++++++++++++++++++++++++++++++
 4 files changed, 349 insertions(+)
 create mode 100644 drivers/iio/adc/max14001.c

diff --git a/MAINTAINERS b/MAINTAINERS
index b8ad615d011f..8c85d0b2d60d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12666,6 +12666,7 @@ L:	linux-iio@vger.kernel.org
 S:	Supported
 W:	https://ez.analog.com/linux-software-drivers
 F:	Documentation/devicetree/bindings/iio/dac/adi,max14001.yaml
+F:	drivers/iio/adc/max14001.c
 
 MAXBOTIX ULTRASONIC RANGER IIO DRIVER
 M:	Andreas Klinger <ak@it-klinger.de>
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index eb2b09ef5d5b..e599d166e98d 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -706,6 +706,16 @@ config MAX11410
 	  To compile this driver as a module, choose M here: the module will be
 	  called max11410.
 
+config MAX14001
+	tristate "Analog Devices MAX14001 ADC driver"
+	depends on SPI
+	help
+	  Say yes here to build support for Analog Devices MAX14001 Configurable,
+	  Isolated 10-bit ADCs for Multi-Range Binary Inputs.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called max14001.
+
 config MAX1241
 	tristate "Maxim max1241 ADC driver"
 	depends on SPI_MASTER
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index e07e4a3e6237..9f8964258f03 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -65,6 +65,7 @@ obj-$(CONFIG_MAX11100) += max11100.o
 obj-$(CONFIG_MAX1118) += max1118.o
 obj-$(CONFIG_MAX11205) += max11205.o
 obj-$(CONFIG_MAX11410) += max11410.o
+obj-$(CONFIG_MAX14001) += max14001.o
 obj-$(CONFIG_MAX1241) += max1241.o
 obj-$(CONFIG_MAX1363) += max1363.o
 obj-$(CONFIG_MAX9611) += max9611.o
diff --git a/drivers/iio/adc/max14001.c b/drivers/iio/adc/max14001.c
new file mode 100644
index 000000000000..b04aa4ba5508
--- /dev/null
+++ b/drivers/iio/adc/max14001.c
@@ -0,0 +1,337 @@
+// SPDX-License-Identifier: (GPL-2.0-only OR BSD-3-Clause)
+/*
+ * Analog Devices MAX14001 ADC driver
+ *
+ * Copyright 2023 Analog Devices Inc.
+ */
+
+#include <linux/bitfield.h>
+#include <linux/bitrev.h>
+#include <linux/device.h>
+#include <linux/iio/iio.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
+#include <linux/spi/spi.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+#include <asm/unaligned.h>
+
+/* MAX14001 Registers Address */
+#define MAX14001_ADC			0x00
+#define MAX14001_FADC			0x01
+#define MAX14001_FLAGS			0x02
+#define MAX14001_FLTEN			0x03
+#define MAX14001_THL			0x04
+#define MAX14001_THU			0x05
+#define MAX14001_INRR			0x06
+#define MAX14001_INRT			0x07
+#define MAX14001_INRP			0x08
+#define MAX14001_CFG			0x09
+#define MAX14001_ENBL			0x0A
+#define MAX14001_ACT			0x0B
+#define MAX14001_WEN			0x0C
+
+#define MAX14001_VERIFICATION_REG(x)	((x) + 0x10)
+
+#define MAX14001_CFG_EXRF		BIT(5)
+
+#define MAX14001_ADDR_MASK		GENMASK(15, 11)
+#define MAX14001_DATA_MASK		GENMASK(9, 0)
+#define MAX14001_FILTER_MASK		GENMASK(3, 2)
+
+#define MAX14001_SET_WRITE_BIT		BIT(10)
+#define MAX14001_WRITE_WEN		0x294
+
+struct max14001_state {
+	struct spi_device	*spi;
+	/*
+	 * lock protect agains multiple concurrent accesses, RMW sequence, and
+	 * SPI transfer
+	 */
+	struct mutex		lock;
+	struct regmap		*regmap;
+	int			vref_mv;
+	/*
+	 * DMA (thus cache coherency maintenance) requires the
+	 * transfer buffers to live in their own cache lines.
+	 */
+	__be16			spi_tx_buffer __aligned(IIO_DMA_MINALIGN);
+	__be16			spi_rx_buffer;
+};
+
+static int max14001_read(void *context, unsigned int reg_addr, unsigned int *data)
+{
+	struct max14001_state *st = context;
+	int ret;
+
+	struct spi_transfer xfers[] = {
+		{
+			.tx_buf = &st->spi_tx_buffer,
+			.len = 2,
+			.cs_change = 1,
+		}, {
+			.rx_buf = &st->spi_rx_buffer,
+			.len = 2,
+		},
+	};
+
+	st->spi_tx_buffer = bitrev16(cpu_to_be16(FIELD_PREP(MAX14001_ADDR_MASK,
+								reg_addr)));
+
+	ret = spi_sync_transfer(st->spi, xfers, ARRAY_SIZE(xfers));
+	if (ret)
+		return ret;
+
+	*data = bitrev16(be16_to_cpu(st->spi_rx_buffer)) & MAX14001_DATA_MASK;
+
+	return 0;
+}
+
+static int max14001_write(void *context, unsigned int reg_addr, unsigned int data)
+{
+	struct max14001_state *st = context;
+
+	st->spi_tx_buffer = bitrev16(cpu_to_be16(
+			FIELD_PREP(MAX14001_ADDR_MASK, reg_addr) |
+			FIELD_PREP(MAX14001_SET_WRITE_BIT, 1) |
+			FIELD_PREP(MAX14001_DATA_MASK, data)));
+
+	return spi_write(st->spi, &st->spi_tx_buffer, sizeof(st->spi_tx_buffer));
+}
+
+static const struct regmap_config max14001_regmap_config = {
+	.reg_read = max14001_read,
+	.reg_write = max14001_write,
+};
+
+static int max14001_write_verification_reg(struct max14001_state *st,
+						unsigned int reg_addr)
+{
+	unsigned int reg_data;
+	int ret;
+
+	ret = max14001_read(st, reg_addr, &reg_data);
+	if (ret)
+		return ret;
+
+	return max14001_write(st, MAX14001_VERIFICATION_REG(reg_addr), reg_data);
+}
+
+static int max14001_reg_update(struct max14001_state *st,
+				unsigned int reg_addr,
+				unsigned int mask,
+				unsigned int val)
+{
+	int ret;
+	unsigned int reg_data;
+
+	/* Enable SPI Registers Write */
+	ret = max14001_write(st, MAX14001_WEN, MAX14001_WRITE_WEN);
+	if (ret)
+		return ret;
+
+	ret = max14001_read(st, reg_addr, &reg_data);
+	if (ret)
+		return ret;
+
+	reg_data = FIELD_PREP(mask, val);
+
+	ret = max14001_write(st, reg_addr, reg_data);
+	if (ret)
+		return ret;
+
+	/* Write Verification Register */
+	ret = max14001_write_verification_reg(st, reg_addr);
+	if (ret)
+		return ret;
+
+	/* Disable SPI Registers Write */
+	return max14001_write(st, MAX14001_WEN, 0);
+}
+
+static int max14001_read_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     int *val, int *val2, long mask)
+{
+	struct max14001_state *st = iio_priv(indio_dev);
+	unsigned int data;
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		mutex_lock(&st->lock);
+		ret = max14001_read(st, MAX14001_ADC, &data);
+		mutex_unlock(&st->lock);
+		if (ret < 0)
+			return ret;
+
+		*val = data;
+
+		return IIO_VAL_INT;
+
+	case IIO_CHAN_INFO_SCALE:
+		*val = st->vref_mv;
+		*val2 = 10;
+
+		return IIO_VAL_FRACTIONAL_LOG2;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info max14001_info = {
+	.read_raw = max14001_read_raw,
+};
+
+static const struct iio_chan_spec max14001_channels[] = {
+	{
+		.type = IIO_VOLTAGE,
+		.channel = 0,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+				      BIT(IIO_CHAN_INFO_SCALE),
+	}
+};
+
+static void max14001_regulator_disable(void *data)
+{
+	struct regulator *reg = data;
+
+	regulator_disable(reg);
+}
+
+static int max14001_init(struct max14001_state *st)
+{
+	int ret;
+
+	/* Enable SPI Registers Write */
+	ret = max14001_write(st, MAX14001_WEN, MAX14001_WRITE_WEN);
+	if (ret)
+		return ret;
+
+	/*
+	 * Reads all registers and writes the values back to their appropriate
+	 * verification registers to clear the Memory Validation fault.
+	 */
+	ret = max14001_write_verification_reg(st, MAX14001_FLTEN);
+	if (ret)
+		return ret;
+
+	ret = max14001_write_verification_reg(st, MAX14001_THL);
+	if (ret)
+		return ret;
+
+	ret = max14001_write_verification_reg(st, MAX14001_THU);
+	if (ret)
+		return ret;
+
+	ret = max14001_write_verification_reg(st, MAX14001_INRR);
+	if (ret)
+		return ret;
+
+	ret = max14001_write_verification_reg(st, MAX14001_INRT);
+	if (ret)
+		return ret;
+
+	ret = max14001_write_verification_reg(st, MAX14001_INRP);
+	if (ret)
+		return ret;
+
+	ret = max14001_write_verification_reg(st, MAX14001_CFG);
+	if (ret)
+		return ret;
+
+	ret = max14001_write_verification_reg(st, MAX14001_ENBL);
+	if (ret)
+		return ret;
+
+	/* Disable SPI Registers Write */
+	return max14001_write(st, MAX14001_WEN, 0);
+}
+
+static int max14001_probe(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev;
+	struct max14001_state *st;
+	struct regulator *vref;
+	struct device *dev = &spi->dev;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	st = iio_priv(indio_dev);
+	st->spi = spi;
+
+	st->regmap = devm_regmap_init(dev, NULL, st, &max14001_regmap_config);
+
+	indio_dev->name = "max14001";
+	indio_dev->info = &max14001_info;
+	indio_dev->channels = max14001_channels;
+	indio_dev->num_channels = ARRAY_SIZE(max14001_channels);
+	indio_dev->modes = INDIO_DIRECT_MODE;
+
+	ret = max14001_init(st);
+	if (ret)
+		return ret;
+
+	vref = devm_regulator_get_optional(dev, "vref");
+	if (IS_ERR(vref)) {
+		if (PTR_ERR(vref) != -ENODEV)
+			return dev_err_probe(dev, PTR_ERR(vref),
+					     "Failed to get vref regulator");
+
+		/* internal reference */
+		st->vref_mv = 1250;
+	} else {
+		ret = regulator_enable(vref);
+		if (ret)
+			return dev_err_probe(dev, ret,
+					"Failed to enable vref regulators\n");
+
+		ret = devm_add_action_or_reset(dev, max14001_regulator_disable,
+					       vref);
+		if (ret)
+			return ret;
+
+		/* select external voltage reference source for the ADC */
+		ret = max14001_reg_update(st, MAX14001_CFG,
+					  MAX14001_CFG_EXRF, 1);
+
+		ret = regulator_get_voltage(vref);
+		if (ret < 0)
+			return dev_err_probe(dev, ret,
+					     "Failed to get vref\n");
+
+		st->vref_mv = ret / 1000;
+	}
+
+	mutex_init(&st->lock);
+
+	return devm_iio_device_register(dev, indio_dev);
+}
+
+static const struct of_device_id max14001_of_match[] = {
+	{ .compatible = "adi,max14001" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, max14001_of_match);
+
+static struct spi_driver max14001_driver = {
+	.driver = {
+		.name = "max14001",
+		.of_match_table = max14001_of_match,
+	},
+	.probe = max14001_probe,
+};
+module_spi_driver(max14001_driver);
+
+MODULE_AUTHOR("Kim Seer Paller");
+MODULE_DESCRIPTION("MAX14001 ADC driver");
+MODULE_LICENSE("GPL");
-- 
2.34.1

Re: [PATCH v3 1/2] dt-bindings:iio:adc: add max14001

[Krzysztof Kozlowski]

On 08/06/2023 19:55, Kim Seer Paller wrote:
> The MAX14001 is configurable, isolated 10-bit ADCs for multi-range
> binary inputs.

Subject: still missing spaces, no improvements.

This is a friendly reminder during the review process.

It seems my previous comments were not fully addressed. Maybe my
feedback got lost between the quotes, maybe you just forgot to apply it.
Please go back to the previous discussion and either implement all
requested changes or keep discussing them.

Thank you.

With subject fixed:

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>


---

This is an automated instruction, just in case, because many review tags
are being ignored. If you do not know the process, here is a short
explanation:

Please add Acked-by/Reviewed-by/Tested-by tags when posting new
versions, under or above your Signed-off-by tag. Tools like b4 can help
here. However, there's no need to repost patches *only* to add the tags.
The upstream maintainer will do that for acks received on the version
they apply.

https://elixir.bootlin.com/linux/v5.17/source/Documentation/process/submitting-patches.rst#L540

Best regards,
Krzysztof

Re: [PATCH v3 2/2] iio: adc: max14001: New driver

[Jonathan Cameron]

On Fri, 9 Jun 2023 01:55:17 +0800
Kim Seer Paller <kimseer.paller@analog.com> wrote:

> The MAX14001 is configurable, isolated 10-bit ADCs for multi-range
> binary inputs.
> 
> Signed-off-by: Kim Seer Paller <kimseer.paller@analog.com>
The driver initialises a regmap then doesn't use it.
Fine not to use it, but get rid of the setup code, structures and include
as well. I assume this got forgotten after testing the code worked when it
wasn't used.

Other than that looks fine to me.

Jonathan