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
21enum ltc2497_chip_type {
22	TYPE_LTC2497,
23	TYPE_LTC2499,
24};
25
26struct 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	/*
32	 * DMA (thus cache coherency maintenance) may require the
33	 * transfer buffers to live in their own cache lines.
34	 */
35	union {
36		__be32 d32;
37		u8 d8[3];
38	} data __aligned(IIO_DMA_MINALIGN);
39};
40
41static int ltc2497_result_and_measure(struct ltc2497core_driverdata *ddata,
42				      u8 address, int *val)
43{
44	struct ltc2497_driverdata *st =
45		container_of(ddata, struct ltc2497_driverdata, common_ddata);
46	int ret;
47
48	if (val) {
49		if (st->recv_size == 3)
50			ret = i2c_master_recv(st->client, (char *)&st->data.d8,
51					      st->recv_size);
52		else
53			ret = i2c_master_recv(st->client, (char *)&st->data.d32,
54					      st->recv_size);
55		if (ret < 0) {
56			dev_err(&st->client->dev, "i2c_master_recv failed\n");
57			return ret;
58		}
59
60		/*
61		 * The data format is 16/24 bit 2s complement, but with an upper sign bit on the
62		 * resolution + 1 position, which is set for positive values only. Given this
63		 * bit's value, subtracting BIT(resolution + 1) from the ADC's result is
64		 * equivalent to a sign extension.
65		 */
66		if (st->recv_size == 3) {
67			*val = (get_unaligned_be24(st->data.d8) >> 6)
68				- BIT(ddata->chip_info->resolution + 1);
69		} else {
70			*val = (be32_to_cpu(st->data.d32) >> 6)
71				- BIT(ddata->chip_info->resolution + 1);
72		}
73
74		/*
75		 * The part started a new conversion at the end of the above i2c
76		 * transfer, so if the address didn't change since the last call
77		 * everything is fine and we can return early.
78		 * If not (which should only happen when some sort of bulk
79		 * conversion is implemented) we have to program the new
80		 * address. Note that this probably fails as the conversion that
81		 * was triggered above is like not complete yet and the two
82		 * operations have to be done in a single transfer.
83		 */
84		if (ddata->addr_prev == address)
85			return 0;
86	}
87
88	ret = i2c_smbus_write_byte(st->client,
89				   LTC2497_ENABLE | address);
90	if (ret)
91		dev_err(&st->client->dev, "i2c transfer failed: %pe\n",
92			ERR_PTR(ret));
93	return ret;
94}
95
96static int ltc2497_probe(struct i2c_client *client)
97{
98	const struct ltc2497_chip_info *chip_info;
99	struct iio_dev *indio_dev;
100	struct ltc2497_driverdata *st;
101	struct device *dev = &client->dev;
102	u32 resolution;
103
104	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C |
105				     I2C_FUNC_SMBUS_WRITE_BYTE))
106		return -EOPNOTSUPP;
107
108	indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
109	if (!indio_dev)
110		return -ENOMEM;
111
112	st = iio_priv(indio_dev);
113	i2c_set_clientdata(client, indio_dev);
114	st->client = client;
115	st->common_ddata.result_and_measure = ltc2497_result_and_measure;
116
117	chip_info = i2c_get_match_data(client);
118	st->common_ddata.chip_info = chip_info;
119
120	resolution = chip_info->resolution;
121	st->recv_size = BITS_TO_BYTES(resolution) + 1;
122
123	return ltc2497core_probe(dev, indio_dev);
124}
125
126static void ltc2497_remove(struct i2c_client *client)
127{
128	struct iio_dev *indio_dev = i2c_get_clientdata(client);
129
130	ltc2497core_remove(indio_dev);
131}
132
133static const struct ltc2497_chip_info ltc2497_info[] = {
134	[TYPE_LTC2497] = {
135		.resolution = 16,
136		.name = NULL,
137	},
138	[TYPE_LTC2499] = {
139		.resolution = 24,
140		.name = "ltc2499",
141	},
142};
143
144static const struct i2c_device_id ltc2497_id[] = {
145	{ "ltc2497", (kernel_ulong_t)&ltc2497_info[TYPE_LTC2497] },
146	{ "ltc2499", (kernel_ulong_t)&ltc2497_info[TYPE_LTC2499] },
147	{ }
148};
149MODULE_DEVICE_TABLE(i2c, ltc2497_id);
150
151static const struct of_device_id ltc2497_of_match[] = {
152	{ .compatible = "lltc,ltc2497", .data = &ltc2497_info[TYPE_LTC2497] },
153	{ .compatible = "lltc,ltc2499", .data = &ltc2497_info[TYPE_LTC2499] },
154	{},
155};
156MODULE_DEVICE_TABLE(of, ltc2497_of_match);
157
158static struct i2c_driver ltc2497_driver = {
159	.driver = {
160		.name = "ltc2497",
161		.of_match_table = ltc2497_of_match,
162	},
163	.probe = ltc2497_probe,
164	.remove = ltc2497_remove,
165	.id_table = ltc2497_id,
166};
167module_i2c_driver(ltc2497_driver);
168
169MODULE_AUTHOR("Michael Hennerich <michael.hennerich@analog.com>");
170MODULE_DESCRIPTION("Linear Technology LTC2497 ADC driver");
171MODULE_LICENSE("GPL v2");
172