ltc2497.c

  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 <linux/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");