Re: [PATCH v3 1/2] hwmon: (max127) Add Maxim MAX127 hardware monitoring driver

From: Guenter Roeck
Date: Mon Nov 23 2020 - 08:17:10 EST

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In reply to: Tao Ren: "Re: [PATCH v3 1/2] hwmon: (max127) Add Maxim MAX127 hardware monitoring driver"
Next in thread: rentao . bupt: "[PATCH v3 2/2] docs: hwmon: Document max127 driver"
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On Sun, Nov 22, 2020 at 11:54:49PM -0800, Tao Ren wrote:
> On Sun, Nov 22, 2020 at 10:33:42AM -0800, Guenter Roeck wrote:
> > On Thu, Nov 19, 2020 at 09:53:23AM -0800, rentao.bupt@xxxxxxxxx wrote:
> > > From: Tao Ren <rentao.bupt@xxxxxxxxx>
> > >
> > > 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@xxxxxxxxx>
> >
> > 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.
>

if (status < 0)
return status;
if (status != 1)
return -EIO;

Again, else after return is not needed (and static analyzers will complain
about it).

Guenter

> >
> > > + 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 <mikechoi@xxxxxx>");
> > > +MODULE_AUTHOR("Tao Ren <rentao.bupt@xxxxxxxxx>");
> > > +MODULE_DESCRIPTION("MAX127 Hardware Monitoring driver");

Next message: Greg Kroah-Hartman: "[PATCH 5.9 017/252] net: ethernet: mtk-star-emac: return ok when xmit drops"
Previous message: Greg Kroah-Hartman: "[PATCH 5.9 018/252] net: ethernet: ti: am65-cpts: update ret when ptp_clock is ERROR"
In reply to: Tao Ren: "Re: [PATCH v3 1/2] hwmon: (max127) Add Maxim MAX127 hardware monitoring driver"
Next in thread: rentao . bupt: "[PATCH v3 2/2] docs: hwmon: Document max127 driver"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]