Re: [PATCH 1/3] hwmon: adm1177: Add ADM1177 Hot Swap Controller and Digital Power Monitor driver

From: Guenter Roeck
Date: Tue Dec 03 2019 - 14:29:00 EST

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On Tue, Dec 03, 2019 at 03:57:09PM +0200, Beniamin Bia wrote:
> ADM1177 is a Hot Swap Controller and Digital Power Monitor with
> Soft Start Pin.
>
> Datasheet:
> Link: https://www.analog.com/media/en/technical-documentation/data-sheets/ADM1177.pdf
>

High level question:

The chip supports setting the current limit, and it reports
the overcurrent status. Any reason for not providing the respective
sysfs entries ?

> Signed-off-by: Beniamin Bia <beniamin.bia@xxxxxxxxxx>
> ---
> drivers/hwmon/Kconfig | 10 ++
> drivers/hwmon/Makefile | 1 +
> drivers/hwmon/adm1177.c | 274 ++++++++++++++++++++++++++++++++++++++++

Please also provide Documentation/hwmon/adm1177.rst.

> 3 files changed, 285 insertions(+)
> create mode 100644 drivers/hwmon/adm1177.c
>
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 5308c59d7001..3db8f5752675 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -164,6 +164,16 @@ config SENSORS_ADM1031
> This driver can also be built as a module. If so, the module
> will be called adm1031.
>
> +config SENSORS_ADM1177
> + tristate "Analog Devices ADM1177 and compatibles"
> + depends on I2C
> + help
> + If you say yes here you get support for Analog Devices ADM1177
> + sensor chips.
> +
> + This driver can also be built as a module. If so, the module
> + will be called adm1177.
> +
> config SENSORS_ADM9240
> tristate "Analog Devices ADM9240 and compatibles"
> depends on I2C
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index 40c036ea45e6..27d04eab1be4 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -34,6 +34,7 @@ obj-$(CONFIG_SENSORS_ADM1025) += adm1025.o
> obj-$(CONFIG_SENSORS_ADM1026) += adm1026.o
> obj-$(CONFIG_SENSORS_ADM1029) += adm1029.o
> obj-$(CONFIG_SENSORS_ADM1031) += adm1031.o
> +obj-$(CONFIG_SENSORS_ADM1177) += adm1177.o
> obj-$(CONFIG_SENSORS_ADM9240) += adm9240.o
> obj-$(CONFIG_SENSORS_ADS7828) += ads7828.o
> obj-$(CONFIG_SENSORS_ADS7871) += ads7871.o
> diff --git a/drivers/hwmon/adm1177.c b/drivers/hwmon/adm1177.c
> new file mode 100644
> index 000000000000..08950cecc9f9
> --- /dev/null
> +++ b/drivers/hwmon/adm1177.c
> @@ -0,0 +1,274 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * ADM1177 Hot Swap Controller and Digital Power Monitor with Soft Start Pin
> + *
> + * Copyright 2015-2019 Analog Devices Inc.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/device.h>
> +#include <linux/init.h>
> +#include <linux/i2c.h>
> +#include <linux/hwmon.h>
> +#include <linux/regulator/consumer.h>

Alphabetic include file order, please.

> +
> +/* Command Byte Operations */
> +#define ADM1177_CMD_V_CONT BIT(0)
> +#define ADM1177_CMD_V_ONCE BIT(1)
> +#define ADM1177_CMD_I_CONT BIT(2)
> +#define ADM1177_CMD_I_ONCE BIT(3)
> +#define ADM1177_CMD_VRANGE BIT(4)
> +#define ADM1177_CMD_STATUS_RD BIT(6)
> +

Requires #include <linux/bits.h>. ADM1177_CMD_STATUS_RD is not used.

> +/* Extended Register */
> +#define ADM1177_REG_ALERT_EN 1

ADM1177_REG_ALERT_EN is not used.

> +#define ADM1177_REG_ALERT_TH 2
> +#define ADM1177_REG_CONTROL 3

ADM1177_REG_CONTROL is not used.

> +
> +/* ADM1177_REG_ALERT_EN */
> +#define ADM1177_EN_ADC_OC1 BIT(0)
> +#define ADM1177_EN_ADC_OC4 BIT(1)
> +#define ADM1177_EN_HS_ALERT BIT(2)
> +#define ADM1177_EN_OFF_ALERT BIT(3)
> +#define ADM1177_CLEAR BIT(4)
> +
> +/* ADM1177_REG_CONTROL */
> +#define ADM1177_SWOFF BIT(0)
> +
> +#define ADM1177_BITS 12

The above defines are not used.

> +
> +/**
> + * struct adm1177_state - driver instance specific data
> + * @client pointer to i2c client
> + * @reg regulator info for the the power supply of the device
> + * @command internal control register
> + * @r_sense_uohm current sense resistor value
> + * @alert_threshold_ua current limit for shutdown
> + * @vrange_high internal voltage divider
> + */
> +struct adm1177_state {
> + struct i2c_client *client;
> + struct regulator *reg;
> + u8 command;
> + u32 r_sense_uohm;
> + u32 alert_threshold_ua;
> + bool vrange_high;
> +};
> +
> +static int adm1177_read_raw(struct adm1177_state *st, u8 num, u8 *data)
> +{
> + struct i2c_client *client = st->client;
> +

That variable seems unncessary. Just use st->client directly, like below.

> + return i2c_master_recv(client, data, num);
> +}
> +
> +static int adm1177_write_cmd(struct adm1177_state *st, u8 cmd)
> +{
> + st->command = cmd;

This is an odd way to record and check if vrange is high or low,
especially since there is already a flag indicating that/if it is high.

Why not just use "if (st->vrange_high) instead of "if (st->command &
ADM1177_CMD_VRANGE") ?

> + return i2c_smbus_write_byte(st->client, cmd);
> +}
> +
> +static int adm1177_read(struct device *dev, enum hwmon_sensor_types type,
> + u32 attr, int channel, long *val)
> +{
> + struct adm1177_state *st = dev_get_drvdata(dev);
> + u8 data[3];
> + long dummy;
> + int ret;
> +
> + switch (type) {
> + case hwmon_curr:
> + ret = adm1177_read_raw(st, 3, data);
> + if (ret < 0)
> + return ret;
> + dummy = (data[1] << 4) | (data[2] & 0xF);
> + /*
> + * convert in milliamperes

convert to

> + * ((105.84mV / 4096) x raw) / senseResistor(ohm)
> + */
> + *val = div_u64((105840000ull * dummy), 4096 * st->r_sense_uohm);
> + return 0;
> + case hwmon_in:
> + ret = adm1177_read_raw(st, 3, data);
> + if (ret < 0)
> + return ret;
> + dummy = (data[0] << 4) | (data[2] >> 4);
> + /*
> + * convert in millivolts based on resistor devision
> + * (V_fullscale / 4096) * raw
> + */
> + if (st->command & ADM1177_CMD_VRANGE)
> + *val = 6650;
> + else
> + *val = 26350;
> +
Dereferencing val several times isn't really very efficient.
How about the following ?

if (st->vrange_high)
dummy *= 26350;
else
dummy *= 6650;
*val = DIV_ROUND_CLOSEST(dummy, 4096);

> + *val = ((*val * dummy) / 4096);
> + return 0;
> + default:
> + return -EOPNOTSUPP;
> + }
> +}
> +
> +static umode_t adm1177_is_visible(const void *data,
> + enum hwmon_sensor_types type,
> + u32 attr, int channel)
> +{
> + const struct adm1177_state *st = data;
> +
> + switch (type) {
> + case hwmon_in:
> + switch (attr) {
> + case hwmon_in_input:
> + return 0444;
> + }
> + break;
> + case hwmon_curr:
> + switch (attr) {
> + case hwmon_curr_input:
> + if (st->r_sense_uohm)
> + return 0444;
> + return 0;
> + }
> + break;
> + default:
> + break;
> + }
> + return 0;
> +}
> +
> +static const u32 adm1177_curr_config[] = {
> + HWMON_C_INPUT,
> + 0
> +};
> +
> +static const struct hwmon_channel_info adm1177_curr = {
> + .type = hwmon_curr,
> + .config = adm1177_curr_config,
> +};
> +
> +static const u32 adm1177_in_config[] = {
> + HWMON_I_INPUT,
> + 0
> +};
> +
> +static const struct hwmon_channel_info adm1177_in = {
> + .type = hwmon_in,
> + .config = adm1177_in_config,
> +};
> +
> +static const struct hwmon_channel_info *adm1177_info[] = {
> + &adm1177_curr,
> + &adm1177_in,
> + NULL
> +};

Please use the HWMON_CHANNEL_INFO macro to declare the above.

> +
> +static const struct hwmon_ops adm1177_hwmon_ops = {
> + .is_visible = adm1177_is_visible,
> + .read = adm1177_read,
> +};
> +
> +static const struct hwmon_chip_info adm1177_chip_info = {
> + .ops = &adm1177_hwmon_ops,
> + .info = adm1177_info,
> +};
> +
> +static void adm1177_remove(void *data)
> +{
> + struct adm1177_state *st = data;
> +
> + regulator_disable(st->reg);
> +}
> +
> +static int adm1177_probe(struct i2c_client *client,
> + const struct i2c_device_id *id)
> +{
> + struct device *dev = &client->dev;
> + struct device *hwmon_dev;
> + struct adm1177_state *st;
> + int ret;
> +
> + st = devm_kzalloc(dev, sizeof(*st), GFP_KERNEL);
> + if (!st)
> + return -ENOMEM;
> +
> + st->client = client;
> +
> + st->reg = devm_regulator_get_optional(&client->dev, "vref");
> + if (IS_ERR(st->reg)) {
> + if (PTR_ERR(st->reg) == -EPROBE_DEFER)
> + return -EPROBE_DEFER;
> +
> + st->reg = NULL;
> + } else {
> + ret = regulator_enable(st->reg);
> + if (ret)
> + return ret;
> + ret = devm_add_action_or_reset(&client->dev, adm1177_remove,
> + st);
> + if (ret)
> + return ret;
> + }
> +
> + if (device_property_read_u32(dev, "adi,r-sense-micro-ohms",
> + &st->r_sense_uohm))
> + st->r_sense_uohm = 1;

Does the default make sense ? A default of 1 mOhm seems to make more sense.

I assume that you explicitly want to be able to disable current sensing
by setting r_sense_uohm to 0. If so, that needs to be documented in the
devicetree file. Also, as written, the property is optional. I think this
also needs to be documented.

> + if (device_property_read_u32(dev, "adi,shutdown-threshold-microamp",
> + &st->alert_threshold_ua))
> + st->alert_threshold_ua = 0;
> + st->vrange_high = device_property_read_bool(dev,
> + "adi,vrange-high-enable");
> + if (st->alert_threshold_ua) {
> + u64 val;
> +
> + val = (0xFFUL * st->alert_threshold_ua * st->r_sense_uohm);

Unnecessary ( )

The above sets val to 0 if st->r_sense_uohm is 0. That means the register
value is set to 0. Does that mean "disable" for the chip ?

> + val = div_u64(val, 105840000U);
> + if (val > 0xFF) {
> + dev_warn(&client->dev,
> + "Requested shutdown current %d uA above limit\n",
> + st->alert_threshold_ua);
> +
> + val = 0xFF;
> + }
> + i2c_smbus_write_byte_data(st->client, ADM1177_REG_ALERT_TH,
> + val);
> + }

Does the chip have a default value ?

> +
> + ret = adm1177_write_cmd(st, ADM1177_CMD_V_CONT |
> + ADM1177_CMD_I_CONT |
> + (st->vrange_high ? 0 : ADM1177_CMD_VRANGE));
> + if (ret)
> + return ret;
> +
> + hwmon_dev =
> + devm_hwmon_device_register_with_info(dev, client->name, st,
> + &adm1177_chip_info, NULL);
> + return PTR_ERR_OR_ZERO(hwmon_dev);
> +}
> +
> +static const struct i2c_device_id adm1177_id[] = {
> + {"adm1177", 0},
> + {}
> +};
> +MODULE_DEVICE_TABLE(i2c, adm1177_id);
> +
> +static const struct of_device_id adm1177_dt_ids[] = {
> + { .compatible = "adi,adm1177" },
> + {},
> +};
> +MODULE_DEVICE_TABLE(of, adm1177_dt_ids);
> +
> +static struct i2c_driver adm1177_driver = {
> + .class = I2C_CLASS_HWMON,
> + .driver = {
> + .name = "adm1177",
> + .of_match_table = adm1177_dt_ids,
> + },
> + .probe = adm1177_probe,
> + .id_table = adm1177_id,
> +};
> +module_i2c_driver(adm1177_driver);
> +
> +MODULE_AUTHOR("Beniamin Bia <beniamin.bia@xxxxxxxxxx>");
> +MODULE_AUTHOR("Michael Hennerich <michael.hennerich@xxxxxxxxxx>");
> +MODULE_DESCRIPTION("Analog Devices ADM1177 ADC driver");
> +MODULE_LICENSE("GPL v2");
> --
> 2.17.1
>

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Previous message: Cong Wang: "Re: [Patch v2 2/3] iommu: optimize iova_magazine_free_pfns()"
In reply to: Guenter Roeck: "Re: [PATCH 2/3] dt-binding: iio: Add documentation for ADM1177"
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