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) requires the
35 * transfer buffers to live in their own cache lines.
36 */
37 uint8_t data[2] ____cacheline_aligned;
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