172 lines · c
1// SPDX-License-Identifier: GPL-2.0-only2/*3 * ltc2497.c - Driver for Analog Devices/Linear Technology LTC2497 ADC4 *5 * Copyright (C) 2017 Analog Devices Inc.6 *7 * Datasheet: http://cds.linear.com/docs/en/datasheet/2497fd.pdf8 */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 the33 * 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 else53 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 the62 * resolution + 1 position, which is set for positive values only. Given this63 * bit's value, subtracting BIT(resolution + 1) from the ADC's result is64 * 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 i2c76 * transfer, so if the address didn't change since the last call77 * everything is fine and we can return early.78 * If not (which should only happen when some sort of bulk79 * conversion is implemented) we have to program the new80 * address. Note that this probably fails as the conversion that81 * was triggered above is like not complete yet and the two82 * 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)<c2497_info[TYPE_LTC2497] },146 { "ltc2499", (kernel_ulong_t)<c2497_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 = <c2497_info[TYPE_LTC2497] },153 { .compatible = "lltc,ltc2499", .data = <c2497_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