cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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ltc2471.c (3597B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/*
      3 * Driver for Linear Technology LTC2471 and LTC2473 voltage monitors
      4 * The LTC2473 is identical to the 2471, but reports a differential signal.
      5 *
      6 * Copyright (C) 2017 Topic Embedded Products
      7 * Author: Mike Looijmans <mike.looijmans@topic.nl>
      8 */
      9
     10#include <linux/err.h>
     11#include <linux/i2c.h>
     12#include <linux/kernel.h>
     13#include <linux/module.h>
     14#include <linux/iio/iio.h>
     15#include <linux/iio/sysfs.h>
     16
     17enum ltc2471_chips {
     18	ltc2471,
     19	ltc2473,
     20};
     21
     22struct ltc2471_data {
     23	struct i2c_client *client;
     24};
     25
     26/* Reference voltage is 1.25V */
     27#define LTC2471_VREF 1250
     28
     29/* Read two bytes from the I2C bus to obtain the ADC result */
     30static int ltc2471_get_value(struct i2c_client *client)
     31{
     32	int ret;
     33	__be16 buf;
     34
     35	ret = i2c_master_recv(client, (char *)&buf, sizeof(buf));
     36	if (ret < 0)
     37		return ret;
     38	if (ret != sizeof(buf))
     39		return -EIO;
     40
     41	/* MSB first */
     42	return be16_to_cpu(buf);
     43}
     44
     45static int ltc2471_read_raw(struct iio_dev *indio_dev,
     46			    struct iio_chan_spec const *chan,
     47			    int *val, int *val2, long info)
     48{
     49	struct ltc2471_data *data = iio_priv(indio_dev);
     50	int ret;
     51
     52	switch (info) {
     53	case IIO_CHAN_INFO_RAW:
     54		ret = ltc2471_get_value(data->client);
     55		if (ret < 0)
     56			return ret;
     57		*val = ret;
     58		return IIO_VAL_INT;
     59
     60	case IIO_CHAN_INFO_SCALE:
     61		if (chan->differential)
     62			/* Output ranges from -VREF to +VREF */
     63			*val = 2 * LTC2471_VREF;
     64		else
     65			/* Output ranges from 0 to VREF */
     66			*val = LTC2471_VREF;
     67		*val2 = 16;	/* 16 data bits */
     68		return IIO_VAL_FRACTIONAL_LOG2;
     69
     70	case IIO_CHAN_INFO_OFFSET:
     71		/* Only differential chip has this property */
     72		*val = -LTC2471_VREF;
     73		return IIO_VAL_INT;
     74
     75	default:
     76		return -EINVAL;
     77	}
     78}
     79
     80static const struct iio_chan_spec ltc2471_channel[] = {
     81	{
     82		.type = IIO_VOLTAGE,
     83		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
     84		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
     85	},
     86};
     87
     88static const struct iio_chan_spec ltc2473_channel[] = {
     89	{
     90		.type = IIO_VOLTAGE,
     91		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
     92		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |
     93					    BIT(IIO_CHAN_INFO_OFFSET),
     94		.differential = 1,
     95	},
     96};
     97
     98static const struct iio_info ltc2471_info = {
     99	.read_raw = ltc2471_read_raw,
    100};
    101
    102static int ltc2471_i2c_probe(struct i2c_client *client,
    103			     const struct i2c_device_id *id)
    104{
    105	struct iio_dev *indio_dev;
    106	struct ltc2471_data *data;
    107	int ret;
    108
    109	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
    110		return -EOPNOTSUPP;
    111
    112	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
    113	if (!indio_dev)
    114		return -ENOMEM;
    115
    116	data = iio_priv(indio_dev);
    117	data->client = client;
    118
    119	indio_dev->name = id->name;
    120	indio_dev->info = &ltc2471_info;
    121	indio_dev->modes = INDIO_DIRECT_MODE;
    122	if (id->driver_data == ltc2473)
    123		indio_dev->channels = ltc2473_channel;
    124	else
    125		indio_dev->channels = ltc2471_channel;
    126	indio_dev->num_channels = 1;
    127
    128	/* Trigger once to start conversion and check if chip is there */
    129	ret = ltc2471_get_value(client);
    130	if (ret < 0) {
    131		dev_err(&client->dev, "Cannot read from device.\n");
    132		return ret;
    133	}
    134
    135	return devm_iio_device_register(&client->dev, indio_dev);
    136}
    137
    138static const struct i2c_device_id ltc2471_i2c_id[] = {
    139	{ "ltc2471", ltc2471 },
    140	{ "ltc2473", ltc2473 },
    141	{}
    142};
    143MODULE_DEVICE_TABLE(i2c, ltc2471_i2c_id);
    144
    145static struct i2c_driver ltc2471_i2c_driver = {
    146	.driver = {
    147		.name = "ltc2471",
    148	},
    149	.probe    = ltc2471_i2c_probe,
    150	.id_table = ltc2471_i2c_id,
    151};
    152
    153module_i2c_driver(ltc2471_i2c_driver);
    154
    155MODULE_DESCRIPTION("LTC2471/LTC2473 ADC driver");
    156MODULE_AUTHOR("Topic Embedded Products");
    157MODULE_LICENSE("GPL v2");