hwmon: (max127) Add Maxim MAX127 hardware monitoring driver
Add hardware monitoring driver for the Maxim MAX127 chip.
MAX127 min/max range handling code is inspired by the max197 driver.
Signed-off-by: Tao Ren <rentao.bupt@gmail.com>
Link: https://lore.kernel.org/r/20201123185658.7632-2-rentao.bupt@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
diff --git a/drivers/hwmon/max127.c b/drivers/hwmon/max127.c
new file mode 100644
index 0000000..402ffdc
--- /dev/null
+++ b/drivers/hwmon/max127.c
@@ -0,0 +1,352 @@
+// 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 <mikechoi@fb.com>");
+MODULE_AUTHOR("Tao Ren <rentao.bupt@gmail.com>");
+MODULE_DESCRIPTION("MAX127 Hardware Monitoring driver");
