xref: /openbmc/linux/drivers/iio/dac/ti-dac7612.c (revision b9ac08b3)
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 
20 struct 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 
dac7612_cmd_single(struct dac7612 * priv,int channel,u16 val)40 static 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 
70 static const struct iio_chan_spec dac7612_channels[] = {
71 	dac7612_CHANNEL(0, "OUTA"),
72 	dac7612_CHANNEL(1, "OUTB"),
73 };
74 
dac7612_read_raw(struct iio_dev * iio_dev,const struct iio_chan_spec * chan,int * val,int * val2,long mask)75 static 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 
dac7612_write_raw(struct iio_dev * iio_dev,const struct iio_chan_spec * chan,int val,int val2,long mask)96 static 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 
119 static const struct iio_info dac7612_info = {
120 	.read_raw = dac7612_read_raw,
121 	.write_raw = dac7612_write_raw,
122 };
123 
dac7612_probe(struct spi_device * spi)124 static 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 
167 static const struct spi_device_id dac7612_id[] = {
168 	{"ti-dac7612"},
169 	{}
170 };
171 MODULE_DEVICE_TABLE(spi, dac7612_id);
172 
173 static const struct of_device_id dac7612_of_match[] = {
174 	{ .compatible = "ti,dac7612" },
175 	{ .compatible = "ti,dac7612u" },
176 	{ .compatible = "ti,dac7612ub" },
177 	{ },
178 };
179 MODULE_DEVICE_TABLE(of, dac7612_of_match);
180 
181 static 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 };
189 module_spi_driver(dac7612_driver);
190 
191 MODULE_AUTHOR("Ricardo Ribalda <ribalda@kernel.org>");
192 MODULE_DESCRIPTION("Texas Instruments DAC7612 DAC driver");
193 MODULE_LICENSE("GPL v2");
194