1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * ltc2497.c - Driver for Analog Devices/Linear Technology LTC2497 ADC
4 *
5 * Copyright (C) 2017 Analog Devices Inc.
6 *
7 * Datasheet: http://cds.linear.com/docs/en/datasheet/2497fd.pdf
8 */
9
10 #include <linux/i2c.h>
11 #include <linux/iio/iio.h>
12 #include <linux/iio/driver.h>
13 #include <linux/module.h>
14 #include <linux/mod_devicetable.h>
15 #include <linux/property.h>
16
17 #include <asm/unaligned.h>
18
19 #include "ltc2497.h"
20
21 enum ltc2497_chip_type {
22 TYPE_LTC2497,
23 TYPE_LTC2499,
24 };
25
26 struct ltc2497_driverdata {
27 /* this must be the first member */
28 struct ltc2497core_driverdata common_ddata;
29 struct i2c_client *client;
30 u32 recv_size;
31 u32 sub_lsb;
32 /*
33 * DMA (thus cache coherency maintenance) may require the
34 * transfer buffers to live in their own cache lines.
35 */
36 union {
37 __be32 d32;
38 u8 d8[3];
39 } data __aligned(IIO_DMA_MINALIGN);
40 };
41
ltc2497_result_and_measure(struct ltc2497core_driverdata * ddata,u8 address,int * val)42 static int ltc2497_result_and_measure(struct ltc2497core_driverdata *ddata,
43 u8 address, int *val)
44 {
45 struct ltc2497_driverdata *st =
46 container_of(ddata, struct ltc2497_driverdata, common_ddata);
47 int ret;
48
49 if (val) {
50 if (st->recv_size == 3)
51 ret = i2c_master_recv(st->client, (char *)&st->data.d8,
52 st->recv_size);
53 else
54 ret = i2c_master_recv(st->client, (char *)&st->data.d32,
55 st->recv_size);
56 if (ret < 0) {
57 dev_err(&st->client->dev, "i2c_master_recv failed\n");
58 return ret;
59 }
60
61 /*
62 * The data format is 16/24 bit 2s complement, but with an upper sign bit on the
63 * resolution + 1 position, which is set for positive values only. Given this
64 * bit's value, subtracting BIT(resolution + 1) from the ADC's result is
65 * equivalent to a sign extension.
66 */
67 if (st->recv_size == 3) {
68 *val = (get_unaligned_be24(st->data.d8) >> st->sub_lsb)
69 - BIT(ddata->chip_info->resolution + 1);
70 } else {
71 *val = (be32_to_cpu(st->data.d32) >> st->sub_lsb)
72 - BIT(ddata->chip_info->resolution + 1);
73 }
74
75 /*
76 * The part started a new conversion at the end of the above i2c
77 * transfer, so if the address didn't change since the last call
78 * everything is fine and we can return early.
79 * If not (which should only happen when some sort of bulk
80 * conversion is implemented) we have to program the new
81 * address. Note that this probably fails as the conversion that
82 * was triggered above is like not complete yet and the two
83 * operations have to be done in a single transfer.
84 */
85 if (ddata->addr_prev == address)
86 return 0;
87 }
88
89 ret = i2c_smbus_write_byte(st->client,
90 LTC2497_ENABLE | address);
91 if (ret)
92 dev_err(&st->client->dev, "i2c transfer failed: %pe\n",
93 ERR_PTR(ret));
94 return ret;
95 }
96
ltc2497_probe(struct i2c_client * client)97 static int ltc2497_probe(struct i2c_client *client)
98 {
99 const struct i2c_device_id *id = i2c_client_get_device_id(client);
100 const struct ltc2497_chip_info *chip_info;
101 struct iio_dev *indio_dev;
102 struct ltc2497_driverdata *st;
103 struct device *dev = &client->dev;
104 u32 resolution;
105
106 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C |
107 I2C_FUNC_SMBUS_WRITE_BYTE))
108 return -EOPNOTSUPP;
109
110 indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
111 if (!indio_dev)
112 return -ENOMEM;
113
114 st = iio_priv(indio_dev);
115 i2c_set_clientdata(client, indio_dev);
116 st->client = client;
117 st->common_ddata.result_and_measure = ltc2497_result_and_measure;
118
119 chip_info = device_get_match_data(dev);
120 if (!chip_info)
121 chip_info = (const struct ltc2497_chip_info *)id->driver_data;
122 st->common_ddata.chip_info = chip_info;
123
124 resolution = chip_info->resolution;
125 st->sub_lsb = 31 - (resolution + 1);
126 st->recv_size = BITS_TO_BYTES(resolution) + 1;
127
128 return ltc2497core_probe(dev, indio_dev);
129 }
130
ltc2497_remove(struct i2c_client * client)131 static void ltc2497_remove(struct i2c_client *client)
132 {
133 struct iio_dev *indio_dev = i2c_get_clientdata(client);
134
135 ltc2497core_remove(indio_dev);
136 }
137
138 static const struct ltc2497_chip_info ltc2497_info[] = {
139 [TYPE_LTC2497] = {
140 .resolution = 16,
141 .name = NULL,
142 },
143 [TYPE_LTC2499] = {
144 .resolution = 24,
145 .name = "ltc2499",
146 },
147 };
148
149 static const struct i2c_device_id ltc2497_id[] = {
150 { "ltc2497", (kernel_ulong_t)<c2497_info[TYPE_LTC2497] },
151 { "ltc2499", (kernel_ulong_t)<c2497_info[TYPE_LTC2499] },
152 { }
153 };
154 MODULE_DEVICE_TABLE(i2c, ltc2497_id);
155
156 static const struct of_device_id ltc2497_of_match[] = {
157 { .compatible = "lltc,ltc2497", .data = <c2497_info[TYPE_LTC2497] },
158 { .compatible = "lltc,ltc2499", .data = <c2497_info[TYPE_LTC2499] },
159 {},
160 };
161 MODULE_DEVICE_TABLE(of, ltc2497_of_match);
162
163 static struct i2c_driver ltc2497_driver = {
164 .driver = {
165 .name = "ltc2497",
166 .of_match_table = ltc2497_of_match,
167 },
168 .probe_new = ltc2497_probe,
169 .remove = ltc2497_remove,
170 .id_table = ltc2497_id,
171 };
172 module_i2c_driver(ltc2497_driver);
173
174 MODULE_AUTHOR("Michael Hennerich <michael.hennerich@analog.com>");
175 MODULE_DESCRIPTION("Linear Technology LTC2497 ADC driver");
176 MODULE_LICENSE("GPL v2");
177