On Sun, Nov 22, 2020 at 10:33:42AM -0800, Guenter Roeck wrote:
> On Thu, Nov 19, 2020 at 09:53:23AM -0800, [email protected] wrote:
> > From: Tao Ren <[email protected]>
> >
> > 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 <[email protected]>
>
> 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.
Thanks for pointing it out. Both includes are deleted in v4.
>
> > +
> > +/*
> > + * 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.
I'm not sure if I understand your suggestion correctly, and I added this
branch to handle the case when i2c_transfer() returns 0, which means the
message is not transferred. Perhaps it would never happen? but anyhow, I
just simplified the check in v4; please kindly review and let me know if
you have further suggestions.
>
> > + 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).
Thanks for pointing it out, and both functions are protected by mutex in
v4.
Cheers,
Tao
>
> > + 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");
