lkml.org 
[lkml]   [2020]   [Nov]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v3 1/2] hwmon: (max127) Add Maxim MAX127 hardware monitoring driver
On Thu, Nov 19, 2020 at 09:53:23AM -0800, rentao.bupt@gmail.com wrote:
> From: Tao Ren <rentao.bupt@gmail.com>
>
> 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>

Nice cleanup. Couple of minor comments.

Thanks,
Guenter

> ---
> Changes in v3:
> - no code change. xdp maintainers were removed from to/cc list.
> Changes in v2:
> - replace devm_hwmon_device_register_with_groups() with
> devm_hwmon_device_register_with_info() API.
> - divide min/max read and write methods to separate functions.
> - fix raw-to-vin conversion logic.
> - refine ctrl_byte handling so mutex is not needed to protect the
> byte.
> - improve i2c_transfer() error handling.
> - a few other improvements (comments, variable naming, and etc.).
>
> drivers/hwmon/Kconfig | 9 ++
> drivers/hwmon/Makefile | 1 +
> drivers/hwmon/max127.c | 346 +++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 356 insertions(+)
> create mode 100644 drivers/hwmon/max127.c
>
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 9d600e0c5584..716df51edc87 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -950,6 +950,15 @@ config SENSORS_MAX1111
> This driver can also be built as a module. If so, the module
> will be called max1111.
>
> +config SENSORS_MAX127
> + tristate "Maxim MAX127 12-bit 8-channel Data Acquisition System"
> + depends on I2C
> + help
> + Say y here to support Maxim's MAX127 DAS chips.
> +
> + This driver can also be built as a module. If so, the module
> + will be called max127.
> +
> config SENSORS_MAX16065
> tristate "Maxim MAX16065 System Manager and compatibles"
> depends on I2C
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index 1083bbfac779..01ca5d3fbad4 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -127,6 +127,7 @@ obj-$(CONFIG_SENSORS_LTC4260) += ltc4260.o
> obj-$(CONFIG_SENSORS_LTC4261) += ltc4261.o
> obj-$(CONFIG_SENSORS_LTQ_CPUTEMP) += ltq-cputemp.o
> obj-$(CONFIG_SENSORS_MAX1111) += max1111.o
> +obj-$(CONFIG_SENSORS_MAX127) += max127.o
> obj-$(CONFIG_SENSORS_MAX16065) += max16065.o
> obj-$(CONFIG_SENSORS_MAX1619) += max1619.o
> obj-$(CONFIG_SENSORS_MAX1668) += max1668.o
> diff --git a/drivers/hwmon/max127.c b/drivers/hwmon/max127.c
> new file mode 100644
> index 000000000000..3df4c225a6a2
> --- /dev/null
> +++ b/drivers/hwmon/max127.c
> @@ -0,0 +1,346 @@
> +// 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/hwmon-sysfs.h>

Not needed.

> +#include <linux/i2c.h>
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/sysfs.h>

Not needed.

> +
> +/*
> + * 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;
> + else if (status != 1)

else after return is not needed.

> + 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;
> + else if (status != 1)

else after return is not needed.

> + 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;
> +
> + 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;

Needs mutex protection to avoid parallel writes (which might mess up
ctrl_byte[channel]).

> +
> + return 0;
> +}
> +
> +static int max127_write_max(struct max127_data *data, int channel, long val)
> +{
> + if (val >= MAX127_FULL_RANGE)
> + data->ctrl_byte[channel] |= MAX127_CTRL_RNG;
> + else
> + data->ctrl_byte[channel] &= ~MAX127_CTRL_RNG;
> +
Same here, to avoid interaction with write_min (which might otherwise
read ctrl and modify it at the same time as this function).

> + 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");

\
 
 \ /
  Last update: 2020-11-22 19:37    [W:0.089 / U:1.604 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site