ti-dac7612.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * DAC7612 Dual, 12-Bit Serial input Digital-to-Analog Converter
  4 *
  5 * Copyright 2019 Qtechnology A/S
  6 * 2019 Ricardo Ribalda <ribalda@kernel.org>
  7 *
  8 * Licensed under the GPL-2.
  9 */
 10#include <linux/kernel.h>
 11#include <linux/module.h>
 12#include <linux/spi/spi.h>
 13#include <linux/gpio/consumer.h>
 14#include <linux/iio/iio.h>
 15
 16#define DAC7612_RESOLUTION 12
 17#define DAC7612_ADDRESS 4
 18#define DAC7612_START 5
 19
 20struct dac7612 {
 21	struct spi_device *spi;
 22	struct gpio_desc *loaddacs;
 23	uint16_t cache[2];
 24
 25	/*
 26	 * Lock to protect the state of the device from potential concurrent
 27	 * write accesses from userspace. The write operation requires an
 28	 * SPI write, then toggling of a GPIO, so the lock aims to protect
 29	 * the sanity of the entire sequence of operation.
 30	 */
 31	struct mutex lock;
 32
 33	/*
 34	 * DMA (thus cache coherency maintenance) may require the
 35	 * transfer buffers to live in their own cache lines.
 36	 */
 37	uint8_t data[2] __aligned(IIO_DMA_MINALIGN);
 38};
 39
 40static int dac7612_cmd_single(struct dac7612 *priv, int channel, u16 val)
 41{
 42	int ret;
 43
 44	priv->data[0] = BIT(DAC7612_START) | (channel << DAC7612_ADDRESS);
 45	priv->data[0] |= val >> 8;
 46	priv->data[1] = val & 0xff;
 47
 48	priv->cache[channel] = val;
 49
 50	ret = spi_write(priv->spi, priv->data, sizeof(priv->data));
 51	if (ret)
 52		return ret;
 53
 54	gpiod_set_value(priv->loaddacs, 1);
 55	gpiod_set_value(priv->loaddacs, 0);
 56
 57	return 0;
 58}
 59
 60#define dac7612_CHANNEL(chan, name) {				\
 61	.type = IIO_VOLTAGE,					\
 62	.channel = (chan),					\
 63	.indexed = 1,						\
 64	.output = 1,						\
 65	.datasheet_name = name,					\
 66	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
 67	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
 68}
 69
 70static const struct iio_chan_spec dac7612_channels[] = {
 71	dac7612_CHANNEL(0, "OUTA"),
 72	dac7612_CHANNEL(1, "OUTB"),
 73};
 74
 75static int dac7612_read_raw(struct iio_dev *iio_dev,
 76			    const struct iio_chan_spec *chan,
 77			    int *val, int *val2, long mask)
 78{
 79	struct dac7612 *priv;
 80
 81	switch (mask) {
 82	case IIO_CHAN_INFO_RAW:
 83		priv = iio_priv(iio_dev);
 84		*val = priv->cache[chan->channel];
 85		return IIO_VAL_INT;
 86
 87	case IIO_CHAN_INFO_SCALE:
 88		*val = 1;
 89		return IIO_VAL_INT;
 90
 91	default:
 92		return -EINVAL;
 93	}
 94}
 95
 96static int dac7612_write_raw(struct iio_dev *iio_dev,
 97			     const struct iio_chan_spec *chan,
 98			     int val, int val2, long mask)
 99{
100	struct dac7612 *priv = iio_priv(iio_dev);
101	int ret;
102
103	if (mask != IIO_CHAN_INFO_RAW)
104		return -EINVAL;
105
106	if ((val >= BIT(DAC7612_RESOLUTION)) || val < 0 || val2)
107		return -EINVAL;
108
109	if (val == priv->cache[chan->channel])
110		return 0;
111
112	mutex_lock(&priv->lock);
113	ret = dac7612_cmd_single(priv, chan->channel, val);
114	mutex_unlock(&priv->lock);
115
116	return ret;
117}
118
119static const struct iio_info dac7612_info = {
120	.read_raw = dac7612_read_raw,
121	.write_raw = dac7612_write_raw,
122};
123
124static int dac7612_probe(struct spi_device *spi)
125{
126	struct iio_dev *iio_dev;
127	struct dac7612 *priv;
128	int i;
129	int ret;
130
131	iio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*priv));
132	if (!iio_dev)
133		return -ENOMEM;
134
135	priv = iio_priv(iio_dev);
136	/*
137	 * LOADDACS pin can be controlled by the driver or externally.
138	 * When controlled by the driver, the DAC value is updated after
139	 * every write.
140	 * When the driver does not control the PIN, the user or an external
141	 * event can change the value of all DACs by pulsing down the LOADDACs
142	 * pin.
143	 */
144	priv->loaddacs = devm_gpiod_get_optional(&spi->dev, "ti,loaddacs",
145						 GPIOD_OUT_LOW);
146	if (IS_ERR(priv->loaddacs))
147		return PTR_ERR(priv->loaddacs);
148	priv->spi = spi;
149	spi_set_drvdata(spi, iio_dev);
150	iio_dev->info = &dac7612_info;
151	iio_dev->modes = INDIO_DIRECT_MODE;
152	iio_dev->channels = dac7612_channels;
153	iio_dev->num_channels = ARRAY_SIZE(priv->cache);
154	iio_dev->name = spi_get_device_id(spi)->name;
155
156	mutex_init(&priv->lock);
157
158	for (i = 0; i < ARRAY_SIZE(priv->cache); i++) {
159		ret = dac7612_cmd_single(priv, i, 0);
160		if (ret)
161			return ret;
162	}
163
164	return devm_iio_device_register(&spi->dev, iio_dev);
165}
166
167static const struct spi_device_id dac7612_id[] = {
168	{"ti-dac7612"},
169	{ }
170};
171MODULE_DEVICE_TABLE(spi, dac7612_id);
172
173static const struct of_device_id dac7612_of_match[] = {
174	{ .compatible = "ti,dac7612" },
175	{ .compatible = "ti,dac7612u" },
176	{ .compatible = "ti,dac7612ub" },
177	{ }
178};
179MODULE_DEVICE_TABLE(of, dac7612_of_match);
180
181static struct spi_driver dac7612_driver = {
182	.driver = {
183		   .name = "ti-dac7612",
184		   .of_match_table = dac7612_of_match,
185		   },
186	.probe = dac7612_probe,
187	.id_table = dac7612_id,
188};
189module_spi_driver(dac7612_driver);
190
191MODULE_AUTHOR("Ricardo Ribalda <ribalda@kernel.org>");
192MODULE_DESCRIPTION("Texas Instruments DAC7612 DAC driver");
193MODULE_LICENSE("GPL v2");