staging:iio:dac: Add AD5421 driver

This patch adds support for the Analog Devices AD5421 Loop-Powered, 4mA to 20mA
DAC.

Signed-off-by: Lars-Peter Clausen <[e-mail]>
Acked-by: Jonathan Cameron <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/iio/dac/Kconfig

···
 	  To compile this driver as module choose M here: the module will be called
 	  ad5360.
 
+config AD5421
+	tristate "Analog Devices AD5421 DAC driver"
+	depends on SPI
+	help
+	  Say yes here to build support for Analog Devices AD5421 loop-powered
+	  digital-to-analog convertors (DAC).
+
+	  To compile this driver as module choose M here: the module will be called
+	  ad5421.
+
 config AD5624R_SPI
 	tristate "Analog Devices AD5624/44/64R DAC spi driver"
 	depends on SPI

drivers/staging/iio/dac/Makefile

···
 #
 
 obj-$(CONFIG_AD5360) += ad5360.o
+obj-$(CONFIG_AD5421) += ad5421.o
 obj-$(CONFIG_AD5624R_SPI) += ad5624r_spi.o
 obj-$(CONFIG_AD5064) += ad5064.o
 obj-$(CONFIG_AD5504) += ad5504.o

drivers/staging/iio/dac/ad5421.c

···
+/*
+ * AD5421 Digital to analog converters  driver
+ *
+ * Copyright 2011 Analog Devices Inc.
+ *
+ * Licensed under the GPL-2.
+ */
+
+#include <linux/device.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/spi/spi.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+
+#include "../iio.h"
+#include "../sysfs.h"
+#include "../events.h"
+#include "dac.h"
+#include "ad5421.h"
+
+
+#define AD5421_REG_DAC_DATA		0x1
+#define AD5421_REG_CTRL			0x2
+#define AD5421_REG_OFFSET		0x3
+#define AD5421_REG_GAIN			0x4
+/* load dac and fault shared the same register number. Writing to it will cause
+ * a dac load command, reading from it will return the fault status register */
+#define AD5421_REG_LOAD_DAC		0x5
+#define AD5421_REG_FAULT		0x5
+#define AD5421_REG_FORCE_ALARM_CURRENT	0x6
+#define AD5421_REG_RESET		0x7
+#define AD5421_REG_START_CONVERSION	0x8
+#define AD5421_REG_NOOP			0x9
+
+#define AD5421_CTRL_WATCHDOG_DISABLE	BIT(12)
+#define AD5421_CTRL_AUTO_FAULT_READBACK	BIT(11)
+#define AD5421_CTRL_MIN_CURRENT		BIT(9)
+#define AD5421_CTRL_ADC_SOURCE_TEMP	BIT(8)
+#define AD5421_CTRL_ADC_ENABLE		BIT(7)
+#define AD5421_CTRL_PWR_DOWN_INT_VREF	BIT(6)
+
+#define AD5421_FAULT_SPI			BIT(15)
+#define AD5421_FAULT_PEC			BIT(14)
+#define AD5421_FAULT_OVER_CURRENT		BIT(13)
+#define AD5421_FAULT_UNDER_CURRENT		BIT(12)
+#define AD5421_FAULT_TEMP_OVER_140		BIT(11)
+#define AD5421_FAULT_TEMP_OVER_100		BIT(10)
+#define AD5421_FAULT_UNDER_VOLTAGE_6V		BIT(9)
+#define AD5421_FAULT_UNDER_VOLTAGE_12V		BIT(8)
+
+/* These bits will cause the fault pin to go high */
+#define AD5421_FAULT_TRIGGER_IRQ \
+	(AD5421_FAULT_SPI | AD5421_FAULT_PEC | AD5421_FAULT_OVER_CURRENT | \
+	AD5421_FAULT_UNDER_CURRENT | AD5421_FAULT_TEMP_OVER_140)
+
+/**
+ * struct ad5421_state - driver instance specific data
+ * @spi:		spi_device
+ * @ctrl:		control register cache
+ * @current_range:	current range which the device is configured for
+ * @data:		spi transfer buffers
+ * @fault_mask:		software masking of events
+ */
+struct ad5421_state {
+	struct spi_device		*spi;
+	unsigned int			ctrl;
+	enum ad5421_current_range	current_range;
+	unsigned int			fault_mask;
+
+	/*
+	 * DMA (thus cache coherency maintenance) requires the
+	 * transfer buffers to live in their own cache lines.
+	 */
+	union {
+		u32 d32;
+		u8 d8[4];
+	} data[2] ____cacheline_aligned;
+};
+
+static const struct iio_chan_spec ad5421_channels[] = {
+	{
+		.type = IIO_CURRENT,
+		.indexed = 1,
+		.output = 1,
+		.channel = 0,
+		.info_mask = IIO_CHAN_INFO_SCALE_SHARED_BIT |
+			IIO_CHAN_INFO_OFFSET_SHARED_BIT |
+			IIO_CHAN_INFO_CALIBSCALE_SEPARATE_BIT |
+			IIO_CHAN_INFO_CALIBBIAS_SEPARATE_BIT,
+		.scan_type = IIO_ST('u', 16, 16, 0),
+		.event_mask = IIO_EV_BIT(IIO_EV_TYPE_THRESH, IIO_EV_DIR_RISING) |
+			IIO_EV_BIT(IIO_EV_TYPE_THRESH, IIO_EV_DIR_FALLING),
+	},
+	{
+		.type = IIO_TEMP,
+		.channel = -1,
+		.event_mask = IIO_EV_BIT(IIO_EV_TYPE_THRESH, IIO_EV_DIR_RISING),
+	},
+};
+
+static int ad5421_write_unlocked(struct iio_dev *indio_dev,
+	unsigned int reg, unsigned int val)
+{
+	struct ad5421_state *st = iio_priv(indio_dev);
+
+	st->data[0].d32 = cpu_to_be32((reg << 16) | val);
+
+	return spi_write(st->spi, &st->data[0].d8[1], 3);
+}
+
+static int ad5421_write(struct iio_dev *indio_dev, unsigned int reg,
+	unsigned int val)
+{
+	int ret;
+
+	mutex_lock(&indio_dev->mlock);
+	ret = ad5421_write_unlocked(indio_dev, reg, val);
+	mutex_unlock(&indio_dev->mlock);
+
+	return ret;
+}
+
+static int ad5421_read(struct iio_dev *indio_dev, unsigned int reg)
+{
+	struct ad5421_state *st = iio_priv(indio_dev);
+	struct spi_message m;
+	int ret;
+	struct spi_transfer t[] = {
+		{
+			.tx_buf = &st->data[0].d8[1],
+			.len = 3,
+			.cs_change = 1,
+		}, {
+			.rx_buf = &st->data[1].d8[1],
+			.len = 3,
+		},
+	};
+
+	spi_message_init(&m);
+	spi_message_add_tail(&t[0], &m);
+	spi_message_add_tail(&t[1], &m);
+
+	mutex_lock(&indio_dev->mlock);
+
+	st->data[0].d32 = cpu_to_be32((1 << 23) | (reg << 16));
+
+	ret = spi_sync(st->spi, &m);
+	if (ret >= 0)
+		ret = be32_to_cpu(st->data[1].d32) & 0xffff;
+
+	mutex_unlock(&indio_dev->mlock);
+
+	return ret;
+}
+
+static int ad5421_update_ctrl(struct iio_dev *indio_dev, unsigned int set,
+	unsigned int clr)
+{
+	struct ad5421_state *st = iio_priv(indio_dev);
+	unsigned int ret;
+
+	mutex_lock(&indio_dev->mlock);
+
+	st->ctrl &= ~clr;
+	st->ctrl |= set;
+
+	ret = ad5421_write_unlocked(indio_dev, AD5421_REG_CTRL, st->ctrl);
+
+	mutex_unlock(&indio_dev->mlock);
+
+	return ret;
+}
+
+static irqreturn_t ad5421_fault_handler(int irq, void *data)
+{
+	struct iio_dev *indio_dev = data;
+	struct ad5421_state *st = iio_priv(indio_dev);
+	unsigned int fault;
+	unsigned int old_fault = 0;
+	unsigned int events;
+
+	fault = ad5421_read(indio_dev, AD5421_REG_FAULT);
+	if (!fault)
+		return IRQ_NONE;
+
+	/* If we had a fault, this might mean that the DAC has lost its state
+	 * and has been reset. Make sure that the control register actually
+	 * contains what we expect it to contain. Otherwise the watchdog might
+	 * be enabled and we get watchdog timeout faults, which will render the
+	 * DAC unusable. */
+	ad5421_update_ctrl(indio_dev, 0, 0);
+
+
+	/* The fault pin stays high as long as a fault condition is present and
+	 * it is not possible to mask fault conditions. For certain fault
+	 * conditions for example like over-temperature it takes some time
+	 * until the fault condition disappears. If we would exit the interrupt
+	 * handler immediately after handling the event it would be entered
+	 * again instantly. Thus we fall back to polling in case we detect that
+	 * a interrupt condition is still present.
+	 */
+	do {
+		/* 0xffff is a invalid value for the register and will only be
+		 * read if there has been a communication error */
+		if (fault == 0xffff)
+			fault = 0;
+
+		/* we are only interested in new events */
+		events = (old_fault ^ fault) & fault;
+		events &= st->fault_mask;
+
+		if (events & AD5421_FAULT_OVER_CURRENT) {
+			iio_push_event(indio_dev,
+				IIO_UNMOD_EVENT_CODE(IIO_CURRENT,
+					0,
+					IIO_EV_TYPE_THRESH,
+					IIO_EV_DIR_RISING),
+			iio_get_time_ns());
+		}
+
+		if (events & AD5421_FAULT_UNDER_CURRENT) {
+			iio_push_event(indio_dev,
+				IIO_UNMOD_EVENT_CODE(IIO_CURRENT,
+					0,
+					IIO_EV_TYPE_THRESH,
+					IIO_EV_DIR_FALLING),
+				iio_get_time_ns());
+		}
+
+		if (events & AD5421_FAULT_TEMP_OVER_140) {
+			iio_push_event(indio_dev,
+				IIO_UNMOD_EVENT_CODE(IIO_TEMP,
+					0,
+					IIO_EV_TYPE_MAG,
+					IIO_EV_DIR_RISING),
+				iio_get_time_ns());
+		}
+
+		old_fault = fault;
+		fault = ad5421_read(indio_dev, AD5421_REG_FAULT);
+
+		/* still active? go to sleep for some time */
+		if (fault & AD5421_FAULT_TRIGGER_IRQ)
+			msleep(1000);
+
+	} while (fault & AD5421_FAULT_TRIGGER_IRQ);
+
+
+	return IRQ_HANDLED;
+}
+
+static void ad5421_get_current_min_max(struct ad5421_state *st,
+	unsigned int *min, unsigned int *max)
+{
+	/* The current range is configured using external pins, which are
+	 * usually hard-wired and not run-time switchable. */
+	switch (st->current_range) {
+	case AD5421_CURRENT_RANGE_4mA_20mA:
+		*min = 4000;
+		*max = 20000;
+		break;
+	case AD5421_CURRENT_RANGE_3mA8_21mA:
+		*min = 3800;
+		*max = 21000;
+		break;
+	case AD5421_CURRENT_RANGE_3mA2_24mA:
+		*min = 3200;
+		*max = 24000;
+		break;
+	default:
+		*min = 0;
+		*max = 1;
+		break;
+	}
+}
+
+static inline unsigned int ad5421_get_offset(struct ad5421_state *st)
+{
+	unsigned int min, max;
+
+	ad5421_get_current_min_max(st, &min, &max);
+	return (min * (1 << 16)) / (max - min);
+}
+
+static inline unsigned int ad5421_get_scale(struct ad5421_state *st)
+{
+	unsigned int min, max;
+
+	ad5421_get_current_min_max(st, &min, &max);
+	return ((max - min) * 1000) / (1 << 16);
+}
+
+static int ad5421_read_raw(struct iio_dev *indio_dev,
+	struct iio_chan_spec const *chan, int *val, int *val2, long m)
+{
+	struct ad5421_state *st = iio_priv(indio_dev);
+	int ret;
+
+	if (chan->type != IIO_CURRENT)
+		return -EINVAL;
+
+	switch (m) {
+	case 0:
+		ret = ad5421_read(indio_dev, AD5421_REG_DAC_DATA);
+		if (ret < 0)
+			return ret;
+		*val = ret;
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		*val = 0;
+		*val2 = ad5421_get_scale(st);
+		return IIO_VAL_INT_PLUS_MICRO;
+	case IIO_CHAN_INFO_OFFSET:
+		*val = ad5421_get_offset(st);
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_CALIBBIAS:
+		ret = ad5421_read(indio_dev, AD5421_REG_OFFSET);
+		if (ret < 0)
+			return ret;
+		*val = ret - 32768;
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_CALIBSCALE:
+		ret = ad5421_read(indio_dev, AD5421_REG_GAIN);
+		if (ret < 0)
+			return ret;
+		*val = ret;
+		return IIO_VAL_INT;
+	}
+
+	return -EINVAL;
+}
+
+static int ad5421_write_raw(struct iio_dev *indio_dev,
+	struct iio_chan_spec const *chan, int val, int val2, long mask)
+{
+	const unsigned int max_val = 1 << 16;
+
+	switch (mask) {
+	case 0:
+		if (val >= max_val || val < 0)
+			return -EINVAL;
+
+		return ad5421_write(indio_dev, AD5421_REG_DAC_DATA, val);
+	case IIO_CHAN_INFO_CALIBBIAS:
+		val += 32768;
+		if (val >= max_val || val < 0)
+			return -EINVAL;
+
+		return ad5421_write(indio_dev, AD5421_REG_OFFSET, val);
+	case IIO_CHAN_INFO_CALIBSCALE:
+		if (val >= max_val || val < 0)
+			return -EINVAL;
+
+		return ad5421_write(indio_dev, AD5421_REG_GAIN, val);
+	default:
+		break;
+	}
+
+	return -EINVAL;
+}
+
+static int ad5421_write_event_config(struct iio_dev *indio_dev,
+	u64 event_code, int state)
+{
+	struct ad5421_state *st = iio_priv(indio_dev);
+	unsigned int mask;
+
+	switch (IIO_EVENT_CODE_EXTRACT_CHAN_TYPE(event_code)) {
+	case IIO_CURRENT:
+		if (IIO_EVENT_CODE_EXTRACT_DIR(event_code) ==
+			IIO_EV_DIR_RISING)
+			mask = AD5421_FAULT_OVER_CURRENT;
+		else
+			mask = AD5421_FAULT_UNDER_CURRENT;
+		break;
+	case IIO_TEMP:
+		mask = AD5421_FAULT_TEMP_OVER_140;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	mutex_lock(&indio_dev->mlock);
+	if (state)
+		st->fault_mask |= mask;
+	else
+		st->fault_mask &= ~mask;
+	mutex_unlock(&indio_dev->mlock);
+
+	return 0;
+}
+
+static int ad5421_read_event_config(struct iio_dev *indio_dev,
+	u64 event_code)
+{
+	struct ad5421_state *st = iio_priv(indio_dev);
+	unsigned int mask;
+
+	switch (IIO_EVENT_CODE_EXTRACT_CHAN_TYPE(event_code)) {
+	case IIO_CURRENT:
+		if (IIO_EVENT_CODE_EXTRACT_DIR(event_code) ==
+			IIO_EV_DIR_RISING)
+			mask = AD5421_FAULT_OVER_CURRENT;
+		else
+			mask = AD5421_FAULT_UNDER_CURRENT;
+		break;
+	case IIO_TEMP:
+		mask = AD5421_FAULT_TEMP_OVER_140;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return (bool)(st->fault_mask & mask);
+}
+
+static int ad5421_read_event_value(struct iio_dev *indio_dev, u64 event_code,
+	int *val)
+{
+	int ret;
+
+	switch (IIO_EVENT_CODE_EXTRACT_CHAN_TYPE(event_code)) {
+	case IIO_CURRENT:
+		ret = ad5421_read(indio_dev, AD5421_REG_DAC_DATA);
+		if (ret < 0)
+			return ret;
+		*val = ret;
+		break;
+	case IIO_TEMP:
+		*val = 140000;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static const struct iio_info ad5421_info = {
+	.read_raw =		ad5421_read_raw,
+	.write_raw =		ad5421_write_raw,
+	.read_event_config =	ad5421_read_event_config,
+	.write_event_config =	ad5421_write_event_config,
+	.read_event_value =	ad5421_read_event_value,
+	.driver_module =	THIS_MODULE,
+};
+
+static int __devinit ad5421_probe(struct spi_device *spi)
+{
+	struct ad5421_platform_data *pdata = dev_get_platdata(&spi->dev);
+	struct iio_dev *indio_dev;
+	struct ad5421_state *st;
+	int ret;
+
+	indio_dev = iio_allocate_device(sizeof(*st));
+	if (indio_dev == NULL) {
+		dev_err(&spi->dev, "Failed to allocate iio device\n");
+		return  -ENOMEM;
+	}
+
+	st = iio_priv(indio_dev);
+	spi_set_drvdata(spi, indio_dev);
+
+	st->spi = spi;
+
+	indio_dev->dev.parent = &spi->dev;
+	indio_dev->name = "ad5421";
+	indio_dev->info = &ad5421_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = ad5421_channels;
+	indio_dev->num_channels = ARRAY_SIZE(ad5421_channels);
+
+	st->ctrl = AD5421_CTRL_WATCHDOG_DISABLE |
+			AD5421_CTRL_AUTO_FAULT_READBACK;
+
+	if (pdata) {
+		st->current_range = pdata->current_range;
+		if (pdata->external_vref)
+			st->ctrl |= AD5421_CTRL_PWR_DOWN_INT_VREF;
+	} else {
+		st->current_range = AD5421_CURRENT_RANGE_4mA_20mA;
+	}
+
+	/* write initial ctrl register value */
+	ad5421_update_ctrl(indio_dev, 0, 0);
+
+	if (spi->irq) {
+		ret = request_threaded_irq(spi->irq,
+					   NULL,
+					   ad5421_fault_handler,
+					   IRQF_TRIGGER_HIGH | IRQF_ONESHOT,
+					   "ad5421 fault",
+					   indio_dev);
+		if (ret)
+			goto error_free;
+	}
+
+	ret = iio_device_register(indio_dev);
+	if (ret) {
+		dev_err(&spi->dev, "Failed to register iio device: %d\n", ret);
+		goto error_free_irq;
+	}
+
+	return 0;
+
+error_free_irq:
+	if (spi->irq)
+		free_irq(spi->irq, indio_dev);
+error_free:
+	iio_free_device(indio_dev);
+
+	return ret;
+}
+
+static int __devexit ad5421_remove(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev = spi_get_drvdata(spi);
+
+	iio_device_unregister(indio_dev);
+	if (spi->irq)
+		free_irq(spi->irq, indio_dev);
+	iio_free_device(indio_dev);
+
+	return 0;
+}
+
+static struct spi_driver ad5421_driver = {
+	.driver = {
+		   .name = "ad5421",
+		   .owner = THIS_MODULE,
+	},
+	.probe = ad5421_probe,
+	.remove = __devexit_p(ad5421_remove),
+};
+
+static __init int ad5421_init(void)
+{
+	return spi_register_driver(&ad5421_driver);
+}
+module_init(ad5421_init);
+
+static __exit void ad5421_exit(void)
+{
+	spi_unregister_driver(&ad5421_driver);
+}
+module_exit(ad5421_exit);
+
+MODULE_AUTHOR("Lars-Peter Clausen <[e-mail]>");
+MODULE_DESCRIPTION("Analog Devices AD5421 DAC");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("spi:ad5421");

drivers/staging/iio/dac/ad5421.h

···
+#ifndef __IIO_DAC_AD5421_H__
+#define __IIO_DAC_AD5421_H__
+
+/*
+ * TODO: This file needs to go into include/linux/iio
+ */
+
+/**
+ * enum ad5421_current_range - Current range the AD5421 is configured for.
+ * @AD5421_CURRENT_RANGE_4mA_20mA: 4 mA to 20 mA (RANGE1,0 pins = 00)
+ * @AD5421_CURRENT_RANGE_3mA8_21mA: 3.8 mA to 21 mA (RANGE1,0 pins = x1)
+ * @AD5421_CURRENT_RANGE_3mA2_24mA: 3.2 mA to 24 mA (RANGE1,0 pins = 10)
+ */
+
+enum ad5421_current_range {
+	AD5421_CURRENT_RANGE_4mA_20mA,
+	AD5421_CURRENT_RANGE_3mA8_21mA,
+	AD5421_CURRENT_RANGE_3mA2_24mA,
+};
+
+/**
+ * struct ad5421_platform_data - AD5421 DAC driver platform data
+ * @external_vref: whether an external reference voltage is used or not
+ * @current_range: Current range the AD5421 is configured for
+ */
+
+struct ad5421_platform_data {
+	bool external_vref;
+	enum ad5421_current_range current_range;
+};
+
+#endif