Message-ID: <20230710042723.46084-2-kimseer.paller@analog.com>
Date:   Mon, 10 Jul 2023 12:27:23 +0800
From:   Kim Seer Paller <kimseer.paller@...log.com>
To:     unlisted-recipients:; (no To-header on input)
CC:     <jic23@...nel.org>, <lars@...afoo.de>, <lgirdwood@...il.com>,
        <broonie@...nel.org>, <Michael.Hennerich@...log.com>,
        <andy.shevchenko@...il.com>, <robh@...nel.org>,
        <krzysztof.kozlowski@...aro.org>, <conor+dt@...nel.org>,
        <kimseer.paller@...log.com>, <linux-iio@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>
Subject: [PATCH v9 2/2] iio: adc: max14001: New driver

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

Signed-off-by: Kim Seer Paller <kimseer.paller@...log.com>
---
V8 -> V9: Changed SPI buffer data types to __le16, removed force cast 
and modified spi buffers bit sequence. Removed max14001_reg_update 
function and directly handled its functionality within the caller. 
Removed unused headers.
V7 -> V8: Added a bitwise OR operation to combine the bitfield element 
with the reg_data value.
V6 -> V7: Swapped ADC external vref source and regulator_get_voltage 
calls. Added forced cast and comment to addressed endian warning.
V5 -> V6: Replaced fixed length assignment with dynamic size 
assignment in xfers struct initialization. Removed .channel 
assignment in max14001_channels definition.
V4 -> V5: No changes.
V3 -> V4: Removed regmap setup, structures, and include.

 MAINTAINERS                |   1 +
 drivers/iio/adc/Kconfig    |  10 ++
 drivers/iio/adc/Makefile   |   1 +
 drivers/iio/adc/max14001.c | 325 +++++++++++++++++++++++++++++++++++++
 4 files changed, 337 insertions(+)
 create mode 100644 drivers/iio/adc/max14001.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 0253058c345b..bd4bbe4f1749 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12797,6 +12797,7 @@ L:	linux-iio@...r.kernel.org
 S:	Supported
 W:	https://ez.analog.com/linux-software-drivers
 F:	Documentation/devicetree/bindings/iio/adc/adi,max14001.yaml
+F:	drivers/iio/adc/max14001.c
 
 MAXBOTIX ULTRASONIC RANGER IIO DRIVER
 M:	Andreas Klinger <ak@...klinger.de>
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index dc14bde31ac1..bdd5033b0733 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 eb6e891790fb..5a825cf9066f 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_MAX77541_ADC) += max77541-adc.o
diff --git a/drivers/iio/adc/max14001.c b/drivers/iio/adc/max14001.c
new file mode 100644
index 000000000000..09686a9faa2e
--- /dev/null
+++ b/drivers/iio/adc/max14001.c
@@ -0,0 +1,325 @@
+// 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/regulator/consumer.h>
+#include <linux/spi/spi.h>
+#include <linux/types.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 against multiple concurrent accesses, RMW sequence, and
+	 * SPI transfer
+	 */
+	struct mutex		lock;
+	int			vref_mv;
+	/*
+	 * DMA (thus cache coherency maintenance) requires the
+	 * transfer buffers to live in their own cache lines.
+	 */
+	__le16			spi_tx_buffer __aligned(IIO_DMA_MINALIGN);
+	__le16			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 = sizeof(st->spi_tx_buffer),
+			.cs_change = 1,
+		}, {
+			.rx_buf = &st->spi_rx_buffer,
+			.len = sizeof(st->spi_rx_buffer),
+		},
+	};
+
+	/*
+	 * Prepare SPI transmit buffer 16 bit-value to big-endian format and
+	 * reverses bit order to align with the LSB-first input on SDI port.
+	 */
+	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;
+
+	/*
+	 * Convert received 16-bit value from big-endian to little-endian format
+	 * and reverses bit order.
+	 */
+	*data = bitrev16(be16_to_cpu(st->spi_rx_buffer));
+
+	return 0;
+}
+
+static int max14001_write(void *context, unsigned int reg_addr, unsigned int data)
+{
+	struct max14001_state *st = context;
+
+	/*
+	 * Prepare SPI transmit buffer 16 bit-value to big-endian format and
+	 * reverses bit order to align with the LSB-first input on SDI port.
+	 */
+	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 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_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,
+		.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;
+	unsigned int reg_data;
+	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 = "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;
+
+		ret = regulator_get_voltage(vref);
+		if (ret < 0)
+			return dev_err_probe(dev, ret,
+					     "Failed to get vref\n");
+
+		st->vref_mv = ret / 1000;
+
+		/*
+		 * Enable SPI registers write and select external voltage
+		 * reference source for the ADC.
+		 */
+		ret = max14001_write(st, MAX14001_WEN, MAX14001_WRITE_WEN);
+		if (ret)
+			return ret;
+
+		ret = max14001_read(st, MAX14001_CFG, &reg_data);
+		if (ret)
+			return ret;
+
+		reg_data |= FIELD_PREP(MAX14001_CFG_EXRF, 1);
+
+		ret = max14001_write(st, MAX14001_CFG, reg_data);
+		if (ret)
+			return ret;
+
+		/* Write Verification Register */
+		ret = max14001_write_verification_reg(st, MAX14001_CFG);
+		if (ret)
+			return ret;
+
+		/* Disable SPI Registers Write */
+		ret = max14001_write(st, MAX14001_WEN, 0);
+		if (ret)
+			return ret;
+	}
+
+	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

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