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- // SPDX-License-Identifier: GPL-2.0+
- /*
- * Hardware monitoring driver for MAX127.
- *
- * Copyright (c) 2020 Facebook Inc.
- */
- #include <linux/err.h>
- #include <linux/hwmon.h>
- #include <linux/i2c.h>
- #include <linux/init.h>
- #include <linux/module.h>
- /*
- * MAX127 Control Byte. Refer to MAX127 datasheet, Table 1 "Control-Byte
- * Format" for details.
- */
- #define MAX127_CTRL_START BIT(7)
- #define MAX127_CTRL_SEL_SHIFT 4
- #define MAX127_CTRL_RNG BIT(3)
- #define MAX127_CTRL_BIP BIT(2)
- #define MAX127_CTRL_PD1 BIT(1)
- #define MAX127_CTRL_PD0 BIT(0)
- #define MAX127_NUM_CHANNELS 8
- #define MAX127_SET_CHANNEL(ch) (((ch) & 7) << MAX127_CTRL_SEL_SHIFT)
- /*
- * MAX127 channel input ranges. Refer to MAX127 datasheet, Table 3 "Range
- * and Polarity Selection" for details.
- */
- #define MAX127_FULL_RANGE 10000 /* 10V */
- #define MAX127_HALF_RANGE 5000 /* 5V */
- /*
- * MAX127 returns 2 bytes at read:
- * - the first byte contains data[11:4].
- * - the second byte contains data[3:0] (MSB) and 4 dummy 0s (LSB).
- * Refer to MAX127 datasheet, "Read a Conversion (Read Cycle)" section
- * for details.
- */
- #define MAX127_DATA_LEN 2
- #define MAX127_DATA_SHIFT 4
- #define MAX127_SIGN_BIT BIT(11)
- struct max127_data {
- struct mutex lock;
- struct i2c_client *client;
- u8 ctrl_byte[MAX127_NUM_CHANNELS];
- };
- static int max127_select_channel(struct i2c_client *client, u8 ctrl_byte)
- {
- int status;
- struct i2c_msg msg = {
- .addr = client->addr,
- .flags = 0,
- .len = sizeof(ctrl_byte),
- .buf = &ctrl_byte,
- };
- status = i2c_transfer(client->adapter, &msg, 1);
- if (status < 0)
- return status;
- if (status != 1)
- return -EIO;
- return 0;
- }
- static int max127_read_channel(struct i2c_client *client, long *val)
- {
- int status;
- u8 i2c_data[MAX127_DATA_LEN];
- struct i2c_msg msg = {
- .addr = client->addr,
- .flags = I2C_M_RD,
- .len = sizeof(i2c_data),
- .buf = i2c_data,
- };
- status = i2c_transfer(client->adapter, &msg, 1);
- if (status < 0)
- return status;
- if (status != 1)
- return -EIO;
- *val = (i2c_data[1] >> MAX127_DATA_SHIFT) |
- ((u16)i2c_data[0] << MAX127_DATA_SHIFT);
- return 0;
- }
- static long max127_process_raw(u8 ctrl_byte, long raw)
- {
- long scale, weight;
- /*
- * MAX127's data coding is binary in unipolar mode with 1 LSB =
- * (Full-Scale/4096) and two’s complement binary in bipolar mode
- * with 1 LSB = [(2 x |FS|)/4096].
- * Refer to MAX127 datasheet, "Transfer Function" section for
- * details.
- */
- scale = (ctrl_byte & MAX127_CTRL_RNG) ? MAX127_FULL_RANGE :
- MAX127_HALF_RANGE;
- if (ctrl_byte & MAX127_CTRL_BIP) {
- weight = (raw & MAX127_SIGN_BIT);
- raw &= ~MAX127_SIGN_BIT;
- raw -= weight;
- raw *= 2;
- }
- return raw * scale / 4096;
- }
- static int max127_read_input(struct max127_data *data, int channel, long *val)
- {
- long raw;
- int status;
- struct i2c_client *client = data->client;
- u8 ctrl_byte = data->ctrl_byte[channel];
- mutex_lock(&data->lock);
- status = max127_select_channel(client, ctrl_byte);
- if (status)
- goto exit;
- status = max127_read_channel(client, &raw);
- if (status)
- goto exit;
- *val = max127_process_raw(ctrl_byte, raw);
- exit:
- mutex_unlock(&data->lock);
- return status;
- }
- static int max127_read_min(struct max127_data *data, int channel, long *val)
- {
- u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
- static const int min_input_map[4] = {
- 0, /* RNG=0, BIP=0 */
- -MAX127_HALF_RANGE, /* RNG=0, BIP=1 */
- 0, /* RNG=1, BIP=0 */
- -MAX127_FULL_RANGE, /* RNG=1, BIP=1 */
- };
- *val = min_input_map[rng_bip];
- return 0;
- }
- static int max127_read_max(struct max127_data *data, int channel, long *val)
- {
- u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
- static const int max_input_map[4] = {
- MAX127_HALF_RANGE, /* RNG=0, BIP=0 */
- MAX127_HALF_RANGE, /* RNG=0, BIP=1 */
- MAX127_FULL_RANGE, /* RNG=1, BIP=0 */
- MAX127_FULL_RANGE, /* RNG=1, BIP=1 */
- };
- *val = max_input_map[rng_bip];
- return 0;
- }
- static int max127_write_min(struct max127_data *data, int channel, long val)
- {
- u8 ctrl;
- mutex_lock(&data->lock);
- ctrl = data->ctrl_byte[channel];
- if (val <= -MAX127_FULL_RANGE) {
- ctrl |= (MAX127_CTRL_RNG | MAX127_CTRL_BIP);
- } else if (val < 0) {
- ctrl |= MAX127_CTRL_BIP;
- ctrl &= ~MAX127_CTRL_RNG;
- } else {
- ctrl &= ~MAX127_CTRL_BIP;
- }
- data->ctrl_byte[channel] = ctrl;
- mutex_unlock(&data->lock);
- return 0;
- }
- static int max127_write_max(struct max127_data *data, int channel, long val)
- {
- mutex_lock(&data->lock);
- if (val >= MAX127_FULL_RANGE)
- data->ctrl_byte[channel] |= MAX127_CTRL_RNG;
- else
- data->ctrl_byte[channel] &= ~MAX127_CTRL_RNG;
- mutex_unlock(&data->lock);
- return 0;
- }
- static umode_t max127_is_visible(const void *_data,
- enum hwmon_sensor_types type,
- u32 attr, int channel)
- {
- if (type == hwmon_in) {
- switch (attr) {
- case hwmon_in_input:
- return 0444;
- case hwmon_in_min:
- case hwmon_in_max:
- return 0644;
- default:
- break;
- }
- }
- return 0;
- }
- static int max127_read(struct device *dev, enum hwmon_sensor_types type,
- u32 attr, int channel, long *val)
- {
- int status;
- struct max127_data *data = dev_get_drvdata(dev);
- if (type != hwmon_in)
- return -EOPNOTSUPP;
- switch (attr) {
- case hwmon_in_input:
- status = max127_read_input(data, channel, val);
- break;
- case hwmon_in_min:
- status = max127_read_min(data, channel, val);
- break;
- case hwmon_in_max:
- status = max127_read_max(data, channel, val);
- break;
- default:
- status = -EOPNOTSUPP;
- break;
- }
- return status;
- }
- static int max127_write(struct device *dev, enum hwmon_sensor_types type,
- u32 attr, int channel, long val)
- {
- int status;
- struct max127_data *data = dev_get_drvdata(dev);
- if (type != hwmon_in)
- return -EOPNOTSUPP;
- switch (attr) {
- case hwmon_in_min:
- status = max127_write_min(data, channel, val);
- break;
- case hwmon_in_max:
- status = max127_write_max(data, channel, val);
- break;
- default:
- status = -EOPNOTSUPP;
- break;
- }
- return status;
- }
- static const struct hwmon_ops max127_hwmon_ops = {
- .is_visible = max127_is_visible,
- .read = max127_read,
- .write = max127_write,
- };
- static const struct hwmon_channel_info *max127_info[] = {
- HWMON_CHANNEL_INFO(in,
- HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
- HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
- HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
- HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
- HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
- HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
- HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
- HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX),
- NULL,
- };
- static const struct hwmon_chip_info max127_chip_info = {
- .ops = &max127_hwmon_ops,
- .info = max127_info,
- };
- static int max127_probe(struct i2c_client *client,
- const struct i2c_device_id *id)
- {
- int i;
- struct device *hwmon_dev;
- struct max127_data *data;
- struct device *dev = &client->dev;
- data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
- if (!data)
- return -ENOMEM;
- data->client = client;
- mutex_init(&data->lock);
- for (i = 0; i < ARRAY_SIZE(data->ctrl_byte); i++)
- data->ctrl_byte[i] = (MAX127_CTRL_START |
- MAX127_SET_CHANNEL(i));
- hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
- data,
- &max127_chip_info,
- NULL);
- return PTR_ERR_OR_ZERO(hwmon_dev);
- }
- static const struct i2c_device_id max127_id[] = {
- { "max127", 0 },
- { }
- };
- MODULE_DEVICE_TABLE(i2c, max127_id);
- static struct i2c_driver max127_driver = {
- .class = I2C_CLASS_HWMON,
- .driver = {
- .name = "max127",
- },
- .probe = max127_probe,
- .id_table = max127_id,
- };
- module_i2c_driver(max127_driver);
- MODULE_LICENSE("GPL");
- MODULE_AUTHOR("Mike Choi <[email protected]>");
- MODULE_AUTHOR("Tao Ren <[email protected]>");
- MODULE_DESCRIPTION("MAX127 Hardware Monitoring driver");
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