Message-ID: <4e9a2383-108a-4440-8f55-77679a79e36e@roeck-us.net>
Date: Tue, 4 Mar 2025 03:38:55 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Dzmitry Sankouski <dsankouski@...il.com>, Jean Delvare
 <jdelvare@...e.com>, Jonathan Corbet <corbet@....net>
Cc: linux-hwmon@...r.kernel.org, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] hwmon: (max77705) add initial support

On 3/4/25 03:08, Dzmitry Sankouski wrote:
> Add support for max77705 hwmon. Includes charger input, system bus, and
> vbyp measurements.
> 
> Signed-off-by: Dzmitry Sankouski <dsankouski@...il.com>
> ---
> Maxim MAX77705 is a Companion Power Management and Type-C interface IC.
> It includes charger and fuel gauge blocks, and is capable of measuring
> charger input current, system bus volatage and current, and bypass
> voltage.

That makes me wonder if this should be implemented in drivers/power/supply/
and utilize the power_supply->hwmon bridge. That seems to make more sense
to me than implementing a separate hwmon driver.

> 
> Add support for mentioned measurements.
> ---
> Changes in v2:
> - EDITME: describe what is new in this series revision.
> - EDITME: use bulletpoints and terse descriptions.
> - Link to v1: https://lore.kernel.org/r/20250225-initial-support-for-max77705-sensors-v1-1-2be6467628b0@gmail.com

???

> ---
> Changes in v2:
> - sort headers alphabetically
> - swap curr channel info, to align indeces with channel_desc struct
> - reword coverletter
> - fix checkpatch --strict warnings
> - remove struct max77705_hwmon, use regmap directly
> - move register validation logic to is_visible function
> - move common register reading and converting logic to separate function
> - remove unnessesary {} in if statement
> - s/i2c->dev/pdev->dev in dev_err_probe
> ---
>   Documentation/hwmon/index.rst    |   1 +
>   Documentation/hwmon/max77705.rst |  39 +++++++++++++++++++++++++++++++++++++++
>   MAINTAINERS                      |   7 +++++++
>   drivers/hwmon/Kconfig            |  10 ++++++++++
>   drivers/hwmon/Makefile           |   1 +
>   drivers/hwmon/max77705-hwmon.c   | 250 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>   6 files changed, 308 insertions(+)
> 
> diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
> index 874f8fd26325..444c7865f74f 100644
> --- a/Documentation/hwmon/index.rst
> +++ b/Documentation/hwmon/index.rst
> @@ -158,6 +158,7 @@ Hardware Monitoring Kernel Drivers
>      max6639
>      max6650
>      max6697
> +   max77705
>      max8688
>      mc13783-adc
>      mc34vr500
> diff --git a/Documentation/hwmon/max77705.rst b/Documentation/hwmon/max77705.rst
> new file mode 100644
> index 000000000000..9037226c50b9
> --- /dev/null
> +++ b/Documentation/hwmon/max77705.rst
> @@ -0,0 +1,39 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +Kernel driver max77705
> +====================
> +
> +Supported chips:
> +
> +  * Maxim Integrated MAX77705
> +
> +    Prefix: 'max77705'
> +
> +    Addresses scanned: none
> +
> +    Datasheet: Not available
> +
> +Authors:
> +      - Dzmitry Sankouski <dsankouski@...il.com>
> +
> +Description
> +-----------
> +
> +The MAX77705 PMIC provides current and voltage measurements besides fuelgauge:
> +- chip input current
> +- system bus current and voltage
> +- VBYP voltage
> +
> +Sysfs Attributes
> +----------------
> +
> +================= ========================================
> +in1_label         "vbyp"
> +in1_input         Measured chip vbyp voltage
> +in2_label         "vsys"
> +in2_input         Measured chip system bus voltage
> +curr1_label       "iin"
> +curr1_input       Measured chip input current.
> +curr2_label       "isys"
> +curr2_input       Measured chip system bus current.
> +================= ========================================
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 29e1a423eee5..0175f9f89325 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -18110,6 +18110,13 @@ S:	Maintained
>   F:	Documentation/hwmon/pc87427.rst
>   F:	drivers/hwmon/pc87427.c
>   
> +MAX77705 HARDWARE MONITORING DRIVER
> +M:	Dzmitry Sankouski <dsankouski@...il.com>
> +L:	linux-hwmon@...r.kernel.org
> +S:	Maintained
> +F:	Documentation/hwmon/max77705.rst
> +F:	drivers/hwmon/max77705-hwmon.c
> +
>   PCA9532 LED DRIVER
>   M:	Riku Voipio <riku.voipio@....fi>
>   S:	Maintained
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 56494ab85b83..c86fe094a978 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -1287,6 +1287,16 @@ config SENSORS_MAX31790
>   	  This driver can also be built as a module. If so, the module
>   	  will be called max31790.
>   
> +config SENSORS_MAX77705
> +	tristate "MAX77705 current and voltage sensor"
> +	depends on I2C
> +	select REGMAP_I2C
> +	help
> +	  If you say yes here you get support for MAX77705 sensors connected with I2C.
> +
> +	  This driver can also be built as a module. If so, the module
> +	  will be called max77705-hwmon.
> +
>   config SENSORS_MC34VR500
>   	tristate "NXP MC34VR500 hardware monitoring driver"
>   	depends on I2C
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index b7ef0f0562d3..ff69f45eca50 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -159,6 +159,7 @@ obj-$(CONFIG_SENSORS_MAX6650)	+= max6650.o
>   obj-$(CONFIG_SENSORS_MAX6697)	+= max6697.o
>   obj-$(CONFIG_SENSORS_MAX31790)	+= max31790.o
>   obj-$(CONFIG_MAX31827) += max31827.o
> +obj-$(CONFIG_SENSORS_MAX77705) += max77705-hwmon.o
>   obj-$(CONFIG_SENSORS_MC13783_ADC)+= mc13783-adc.o
>   obj-$(CONFIG_SENSORS_MC34VR500)	+= mc34vr500.o
>   obj-$(CONFIG_SENSORS_MCP3021)	+= mcp3021.o
> diff --git a/drivers/hwmon/max77705-hwmon.c b/drivers/hwmon/max77705-hwmon.c
> new file mode 100644
> index 000000000000..6d2161421ac7
> --- /dev/null
> +++ b/drivers/hwmon/max77705-hwmon.c
> @@ -0,0 +1,250 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + *  MAX77705 voltage and current hwmon driver.
> + *
> + *  Copyright (C) 2025 Dzmitry Sankouski <dsankouski@...il.com>
> + */
> +
> +#include <linux/err.h>
> +#include <linux/hwmon-sysfs.h>

Not needed.

> +#include <linux/hwmon.h>
> +#include <linux/i2c.h>
> +#include <linux/jiffies.h>
> +#include <linux/kernel.h>
> +#include <linux/mfd/max77705-private.h>

Doesn't exist.

> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +#include <linux/slab.h>
> +
> +struct channel_desc {
> +	u8 reg;
> +	u8 avg_reg;
> +	const char *const label;
> +	// register resolution. nano Volts for voltage, nano Amperes for current
> +	u64 resolution;

u64 is unnecessary. See below.

> +};
> +
> +static const struct channel_desc current_channel_desc[] = {
> +	{
> +		.reg = IIN_REG,
> +		.label = "IIN_REG",
> +		.resolution = 125000
> +	},
> +	{
> +		.reg = ISYS_REG,
> +		.avg_reg = AVGISYS_REG,
> +		.label = "ISYS_REG",
> +		.resolution = 312500
> +	}
> +};
> +
> +static const struct channel_desc voltage_channel_desc[] = {
> +	{
> +		.reg = VBYP_REG,
> +		.label = "VBYP_REG",
> +		.resolution = 427246
> +	},
> +	{
> +		.reg = VSYS_REG,
> +		.label = "VSYS_REG",
> +		.resolution = 156250
> +	}
> +};
> +
> +static const struct regmap_range max77705_hwmon_readable_ranges[] = {
> +	regmap_reg_range(AVGISYS_REG,	AVGISYS_REG + 1),
> +	regmap_reg_range(IIN_REG,	IIN_REG + 1),
> +	regmap_reg_range(ISYS_REG,	ISYS_REG + 1),
> +	regmap_reg_range(VBYP_REG,	VBYP_REG + 1),
> +	regmap_reg_range(VSYS_REG,	VSYS_REG + 1),
> +};
> +
> +static const struct regmap_access_table max77705_hwmon_readable_table = {
> +	.yes_ranges = max77705_hwmon_readable_ranges,
> +	.n_yes_ranges = ARRAY_SIZE(max77705_hwmon_readable_ranges),
> +};
> +
> +static const struct regmap_config max77705_hwmon_regmap_config = {
> +	.name = "max77705_hwmon",
> +	.reg_bits = 8,
> +	.val_bits = 16,
> +	.rd_table = &max77705_hwmon_readable_table,
> +	.max_register = MAX77705_FG_END,
> +	.val_format_endian = REGMAP_ENDIAN_LITTLE
> +};
> +
> +static int max77705_read_and_convert(struct regmap *regmap, u8 reg, u64 res, long *val)

u64 is unnecessary for res.

> +{
> +	int ret;
> +	u32 regval;
> +
> +	ret = regmap_read(regmap, reg, &regval);
> +	if (ret < 0)
> +		return ret;
> +	*val = mult_frac((long)regval, res, 1000000);

This won't build on 32-bit systems. You'll need to use DIV_ROUND_CLOSEST_ULL(),
and the conversion to 64-bit can be done with
	*val = DIV_ROUND_CLOSEST_ULL((u64)regval * res, 1000000);

> +
> +	return 0;
> +}
> +
> +static umode_t max77705_is_visible(const void *data,
> +				   enum hwmon_sensor_types type,
> +				   u32 attr, int channel)
> +{
> +	switch (type) {
> +	case hwmon_in:
> +		if (channel >= ARRAY_SIZE(voltage_channel_desc))
> +			return 0;
> +
> +		switch (attr) {
> +		case hwmon_in_input:
> +		case hwmon_in_label:
> +			return 0444;
> +		default:
> +			break;
> +		}
> +		break;
> +	case hwmon_curr:
> +		if (channel >= ARRAY_SIZE(current_channel_desc))
> +			return 0;
> +
> +		switch (attr) {
> +		case hwmon_curr_input:
> +		case hwmon_in_label:
> +			return 0444;
> +		case hwmon_curr_average:
> +			if (current_channel_desc[channel].avg_reg)
> +				return 0444;
> +		default:
> +			break;
> +		}
> +		break;

The chip provides temperature measurements. Why not support it ?

Also, how about limits ? Doesn't the chip support any ? There do
seem to be some threshold registers.

> +	default:
> +		break;
> +	}
> +	return 0;
> +}
> +
> +static int max77705_read_string(struct device *dev, enum hwmon_sensor_types type, u32 attr,
> +				int channel, const char **buf)
> +{
> +	switch (type) {
> +	case hwmon_curr:
> +		switch (attr) {
> +		case hwmon_in_label:
> +			*buf = current_channel_desc[channel].label;
> +			return 0;
> +		default:
> +			return -EOPNOTSUPP;
> +		}
> +
> +	case hwmon_in:
> +		switch (attr) {
> +		case hwmon_in_label:
> +			*buf = voltage_channel_desc[channel].label;
> +			return 0;
> +		default:
> +			return -EOPNOTSUPP;
> +		}
> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +}
> +
> +static int max77705_read(struct device *dev, enum hwmon_sensor_types type,
> +			 u32 attr, int channel, long *val)
> +{
> +	struct regmap *regmap = dev_get_drvdata(dev);
> +	u8 reg;
> +	u64 res;
> +
> +	switch (type) {
> +	case hwmon_curr:
> +		switch (attr) {
> +		case hwmon_curr_input:
> +			reg = current_channel_desc[channel].reg;
> +			res = current_channel_desc[channel].resolution;
> +
> +			return max77705_read_and_convert(regmap, reg, res, val);
> +		case hwmon_curr_average:
> +			reg = current_channel_desc[channel].avg_reg;
> +			res = current_channel_desc[channel].resolution;
> +
> +			return max77705_read_and_convert(regmap, reg, res, val);
> +		default:
> +			return -EOPNOTSUPP;
> +		}
> +
> +	case hwmon_in:
> +		switch (attr) {
> +		case hwmon_in_input:
> +			reg = voltage_channel_desc[channel].reg;
> +			res = voltage_channel_desc[channel].resolution;
> +
> +			return max77705_read_and_convert(regmap, reg, res, val);
> +		default:
> +			return -EOPNOTSUPP;
> +		}
> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct hwmon_ops max77705_hwmon_ops = {
> +	.is_visible = max77705_is_visible,
> +	.read = max77705_read,
> +	.read_string = max77705_read_string,
> +};
> +
> +static const struct hwmon_channel_info *max77705_info[] = {
> +	HWMON_CHANNEL_INFO(in,
> +			   HWMON_I_INPUT | HWMON_I_LABEL,
> +			   HWMON_I_INPUT | HWMON_I_LABEL
> +			),
> +	HWMON_CHANNEL_INFO(curr,
> +			   HWMON_C_INPUT | HWMON_C_LABEL,
> +			   HWMON_C_INPUT | HWMON_C_AVERAGE | HWMON_C_LABEL
> +			),
> +	NULL
> +};
> +
> +static const struct hwmon_chip_info max77705_chip_info = {
> +	.ops = &max77705_hwmon_ops,
> +	.info = max77705_info,
> +};
> +
> +static int max77705_hwmon_probe(struct platform_device *pdev)
> +{
> +	struct i2c_client *i2c;
> +	struct device *hwmon_dev;
> +	struct regmap *regmap;
> +
> +	i2c = to_i2c_client(pdev->dev.parent);
> +	regmap = devm_regmap_init_i2c(i2c, &max77705_hwmon_regmap_config);

I still think this is unnecessarily restrictive, and that the mfd driver
should register the regmap.

> +	if (IS_ERR(regmap))
> +		return dev_err_probe(&pdev->dev, PTR_ERR(regmap),
> +				"Failed to register max77705 hwmon regmap\n");
> +
> +	hwmon_dev = devm_hwmon_device_register_with_info(&pdev->dev, "max77705", regmap,
> +							 &max77705_chip_info, NULL);
> +	if (IS_ERR(hwmon_dev))
> +		return dev_err_probe(&pdev->dev, PTR_ERR(hwmon_dev),
> +				"Unable to register hwmon device\n");
> +
> +	return 0;
> +};
> +
> +static struct platform_driver max77705_hwmon_driver = {
> +	.driver = {
> +		.name = "max77705-hwmon",
> +	},
> +	.probe = max77705_hwmon_probe,
> +};
> +
> +module_platform_driver(max77705_hwmon_driver);
> +
> +MODULE_AUTHOR("Dzmitry Sankouski <dsankouski@...il.com>");
> +MODULE_DESCRIPTION("MAX77705 monitor driver");
> +MODULE_LICENSE("GPL");
> +
> 
> ---
> base-commit: 20d5c66e1810e6e8805ec0d01373afb2dba9f51a
> change-id: 20250123-initial-support-for-max77705-sensors-ad0170ac1ec5
> 
> Best regards,

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