Re: [PATCH v8 3/3] hwmon: add Gateworks System Controller support

[Guenter Roeck]

On Fri, Mar 27, 2020 at 01:33:34PM -0700, Tim Harvey wrote:
> The Gateworks System Controller has a hwmon sub-component that exposes
> up to 16 ADC's, some of which are temperature sensors, others which are
> voltage inputs. The ADC configuration (register mapping and name) is
> configured via device-tree and varies board to board.
> 
> Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
> Signed-off-by: Tim Harvey <tharvey@xxxxxxxxxxxxx>

For my own reference:

Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>

Guenter

> ---
> v8:
> - move regmap init to hwmon
> 
> v7:
> - fix whitespace in Kconfig
> - remove unnecessary device pointer in private data
> - change divider from mili-ohms to ohms
> - move fan base property to reg
> 
> v6:
> - fix size of info field
> - improve pwm output control documentation
> - include unit suffix in divider and offset
> - change subnode name to gsc-adc
> - change to fan subnode
> - fix voltage offset
> 
> v5:
> - fix various checkpatch issues
> - correct gsc-hwmon.rst in MAINTAINERS
> - encorporate Gunter's feedback:
>  - switch to SENSOR_DEVICE_ATTR_{RW,RO}
>  - use tmp value to avoid excessive pointer deference
>  - simplify shift operation
>  - scale voffset once
>  - simplify is_visible function
>  - remove empty line at end of file
> 
> v4:
> - adjust for uV offset from device-tree
> - remove unnecessary optional write function
> - remove register range check
> - change dev_err prints to use gsc dev
> - hard-code resolution/scaling for raw adcs
> - describe units of ADC resolution
> - move to using pwm<n>_auto_point<m>_{pwm,temp} for FAN PWM
> - ensure space before/after operators
> - remove unnecessary parens
> - remove more debugging
> - add default case and comment for type_voltage
> - remove unnecessary index bounds checks for channel
> - remove unnecessary clearing of struct fields
> - added Documentation/hwmon/gsc-hwmon.rst
> 
> v3:
> - add voltage_raw input type and supporting fields
> - add channel validation to is_visible function
> - remove unnecessary channel validation from read/write functions
> 
> v2:
> - change license comment style
> - remove DEBUG
> - simplify regmap_bulk_read err check
> - remove break after returns in switch statement
> - fix fan setpoint buffer address
> - remove unnecessary parens
> - consistently use struct device *dev pointer
> - change license/comment block
> - add validation for hwmon child node props
> - move parsing of of to own function
> - use strlcpy to ensure null termination
> - fix static array sizes and removed unnecessary initializers
> - dynamically allocate channels
> - fix fan input label
> - support platform data
> - fixed whitespace issues
> ---
>  Documentation/hwmon/gsc-hwmon.rst       |  53 +++++
>  Documentation/hwmon/index.rst           |   1 +
>  MAINTAINERS                             |   3 +
>  drivers/hwmon/Kconfig                   |   9 +
>  drivers/hwmon/Makefile                  |   1 +
>  drivers/hwmon/gsc-hwmon.c               | 385 ++++++++++++++++++++++++++++++++
>  include/linux/platform_data/gsc_hwmon.h |  44 ++++
>  7 files changed, 496 insertions(+)
>  create mode 100644 Documentation/hwmon/gsc-hwmon.rst
>  create mode 100644 drivers/hwmon/gsc-hwmon.c
>  create mode 100644 include/linux/platform_data/gsc_hwmon.h
> 
> diff --git a/Documentation/hwmon/gsc-hwmon.rst b/Documentation/hwmon/gsc-hwmon.rst
> new file mode 100644
> index 00000000..ffac392
> --- /dev/null
> +++ b/Documentation/hwmon/gsc-hwmon.rst
> @@ -0,0 +1,53 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +Kernel driver gsc-hwmon
> +=======================
> +
> +Supported chips: Gateworks GSC
> +Datasheet: http://trac.gateworks.com/wiki/gsc
> +Author: Tim Harvey <tharvey@xxxxxxxxxxxxx>
> +
> +Description:
> +------------
> +
> +This driver supports hardware monitoring for the temperature sensor,
> +various ADC's connected to the GSC, and optional FAN controller available
> +on some boards.
> +
> +
> +Voltage Monitoring
> +------------------
> +
> +The voltage inputs are scaled either internally or by the driver depending
> +on the GSC version and firmware. The values returned by the driver do not need
> +further scaling. The voltage input labels provide the voltage rail name:
> +
> +inX_input                  Measured voltage (mV).
> +inX_label                  Name of voltage rail.
> +
> +
> +Temperature Monitoring
> +----------------------
> +
> +Temperatures are measured with 12-bit or 10-bit resolution and are scaled
> +either internally or by the driver depending on the GSC version and firmware.
> +The values returned by the driver reflect millidegree Celcius:
> +
> +tempX_input                Measured temperature.
> +tempX_label                Name of temperature input.
> +
> +
> +PWM Output Control
> +------------------
> +
> +The GSC features 1 PWM output that operates in automatic mode where the
> +PWM value will be scalled depending on 6 temperature boundaries.
> +The tempeature boundaries are read-write and in millidegree Celcius and the
> +read-only PWM values range from 0 (off) to 255 (full speed).
> +Fan speed will be set to minimum (off) when the temperature sensor reads
> +less than pwm1_auto_point1_temp and maximum when the temperature sensor
> +equals or exceeds pwm1_auto_point6_temp.
> +
> +pwm1_auto_point[1-6]_pwm       PWM value.
> +pwm1_auto_point[1-6]_temp      Temperature boundary.
> +
> diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
> index 43cc605..a4fab69 100644
> --- a/Documentation/hwmon/index.rst
> +++ b/Documentation/hwmon/index.rst
> @@ -58,6 +58,7 @@ Hardware Monitoring Kernel Drivers
>     ftsteutates
>     g760a
>     g762
> +   gsc-hwmon
>     gl518sm
>     hih6130
>     ibmaem
> diff --git a/MAINTAINERS b/MAINTAINERS
> index bb79b60..3f15542 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -6846,6 +6846,9 @@ S:	Maintained
>  F:	Documentation/devicetree/bindings/mfd/gateworks-gsc.yaml
>  F:	drivers/mfd/gateworks-gsc.c
>  F:	include/linux/mfd/gsc.h
> +F:	Documentation/hwmon/gsc-hwmon.rst
> +F:	drivers/hwmon/gsc-hwmon.c
> +F:	include/linux/platform_data/gsc_hwmon.h
>  
>  GCC PLUGINS
>  M:	Kees Cook <keescook@xxxxxxxxxxxx>
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 23dfe84..47b8761 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -494,6 +494,15 @@ config SENSORS_F75375S
>  	  This driver can also be built as a module. If so, the module
>  	  will be called f75375s.
>  
> +config SENSORS_GSC
> +	tristate "Gateworks System Controller ADC"
> +	depends on MFD_GATEWORKS_GSC
> +	help
> +	  Support for the Gateworks System Controller A/D converters.
> +
> +	  To compile this driver as a module, choose M here:
> +	  the module will be called gsc-hwmon.
> +
>  config SENSORS_MC13783_ADC
>          tristate "Freescale MC13783/MC13892 ADC"
>          depends on MFD_MC13XXX
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index 6db5db9..259cba7 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -71,6 +71,7 @@ obj-$(CONFIG_SENSORS_G760A)	+= g760a.o
>  obj-$(CONFIG_SENSORS_G762)	+= g762.o
>  obj-$(CONFIG_SENSORS_GL518SM)	+= gl518sm.o
>  obj-$(CONFIG_SENSORS_GL520SM)	+= gl520sm.o
> +obj-$(CONFIG_SENSORS_GSC)	+= gsc-hwmon.o
>  obj-$(CONFIG_SENSORS_GPIO_FAN)	+= gpio-fan.o
>  obj-$(CONFIG_SENSORS_HIH6130)	+= hih6130.o
>  obj-$(CONFIG_SENSORS_ULTRA45)	+= ultra45_env.o
> diff --git a/drivers/hwmon/gsc-hwmon.c b/drivers/hwmon/gsc-hwmon.c
> new file mode 100644
> index 00000000..d5cdd92
> --- /dev/null
> +++ b/drivers/hwmon/gsc-hwmon.c
> @@ -0,0 +1,385 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Driver for Gateworks System Controller Hardware Monitor module
> + *
> + * Copyright (C) 2020 Gateworks Corporation
> + */
> +#include <linux/hwmon.h>
> +#include <linux/hwmon-sysfs.h>
> +#include <linux/mfd/gsc.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +#include <linux/slab.h>
> +
> +#include <linux/platform_data/gsc_hwmon.h>
> +
> +#define GSC_HWMON_MAX_TEMP_CH	16
> +#define GSC_HWMON_MAX_IN_CH	16
> +
> +#define GSC_HWMON_RESOLUTION	12
> +#define GSC_HWMON_VREF		2500
> +
> +struct gsc_hwmon_data {
> +	struct gsc_dev *gsc;
> +	struct gsc_hwmon_platform_data *pdata;
> +	struct regmap *regmap;
> +	const struct gsc_hwmon_channel *temp_ch[GSC_HWMON_MAX_TEMP_CH];
> +	const struct gsc_hwmon_channel *in_ch[GSC_HWMON_MAX_IN_CH];
> +	u32 temp_config[GSC_HWMON_MAX_TEMP_CH + 1];
> +	u32 in_config[GSC_HWMON_MAX_IN_CH + 1];
> +	struct hwmon_channel_info temp_info;
> +	struct hwmon_channel_info in_info;
> +	const struct hwmon_channel_info *info[3];
> +	struct hwmon_chip_info chip;
> +};
> +
> +static const struct regmap_config gsc_hwmon_regmap_config = {
> +	.reg_bits = 8,
> +	.val_bits = 8,
> +	.cache_type = REGCACHE_NONE,
> +};
> +
> +static ssize_t pwm_auto_point_temp_show(struct device *dev,
> +					struct device_attribute *devattr,
> +					char *buf)
> +{
> +	struct gsc_hwmon_data *hwmon = dev_get_drvdata(dev);
> +	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
> +	u8 reg = hwmon->pdata->fan_base + (2 * attr->index);
> +	u8 regs[2];
> +	int ret;
> +
> +	ret = regmap_bulk_read(hwmon->regmap, reg, regs, 2);
> +	if (ret)
> +		return ret;
> +
> +	ret = regs[0] | regs[1] << 8;
> +	return sprintf(buf, "%d\n", ret * 10);
> +}
> +
> +static ssize_t pwm_auto_point_temp_store(struct device *dev,
> +					 struct device_attribute *devattr,
> +					 const char *buf, size_t count)
> +{
> +	struct gsc_hwmon_data *hwmon = dev_get_drvdata(dev);
> +	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
> +	u8 reg = hwmon->pdata->fan_base + (2 * attr->index);
> +	u8 regs[2];
> +	long temp;
> +	int err;
> +
> +	if (kstrtol(buf, 10, &temp))
> +		return -EINVAL;
> +
> +	temp = clamp_val(temp, 0, 10000);
> +	temp = DIV_ROUND_CLOSEST(temp, 10);
> +
> +	regs[0] = temp & 0xff;
> +	regs[1] = (temp >> 8) & 0xff;
> +	err = regmap_bulk_write(hwmon->regmap, reg, regs, 2);
> +	if (err)
> +		return err;
> +
> +	return count;
> +}
> +
> +static ssize_t pwm_auto_point_pwm_show(struct device *dev,
> +				       struct device_attribute *devattr,
> +				       char *buf)
> +{
> +	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
> +
> +	return sprintf(buf, "%d\n", 255 * (50 + (attr->index * 10)) / 100);
> +}
> +
> +static SENSOR_DEVICE_ATTR_RO(pwm1_auto_point1_pwm, pwm_auto_point_pwm, 0);
> +static SENSOR_DEVICE_ATTR_RW(pwm1_auto_point1_temp, pwm_auto_point_temp, 0);
> +
> +static SENSOR_DEVICE_ATTR_RO(pwm1_auto_point2_pwm, pwm_auto_point_pwm, 1);
> +static SENSOR_DEVICE_ATTR_RW(pwm1_auto_point2_temp, pwm_auto_point_temp, 1);
> +
> +static SENSOR_DEVICE_ATTR_RO(pwm1_auto_point3_pwm, pwm_auto_point_pwm, 2);
> +static SENSOR_DEVICE_ATTR_RW(pwm1_auto_point3_temp, pwm_auto_point_temp, 2);
> +
> +static SENSOR_DEVICE_ATTR_RO(pwm1_auto_point4_pwm, pwm_auto_point_pwm, 3);
> +static SENSOR_DEVICE_ATTR_RW(pwm1_auto_point4_temp, pwm_auto_point_temp, 3);
> +
> +static SENSOR_DEVICE_ATTR_RO(pwm1_auto_point5_pwm, pwm_auto_point_pwm, 4);
> +static SENSOR_DEVICE_ATTR_RW(pwm1_auto_point5_temp, pwm_auto_point_temp, 4);
> +
> +static SENSOR_DEVICE_ATTR_RO(pwm1_auto_point6_pwm, pwm_auto_point_pwm, 5);
> +static SENSOR_DEVICE_ATTR_RW(pwm1_auto_point6_temp, pwm_auto_point_temp, 5);
> +
> +static struct attribute *gsc_hwmon_attributes[] = {
> +	&sensor_dev_attr_pwm1_auto_point1_pwm.dev_attr.attr,
> +	&sensor_dev_attr_pwm1_auto_point1_temp.dev_attr.attr,
> +	&sensor_dev_attr_pwm1_auto_point2_pwm.dev_attr.attr,
> +	&sensor_dev_attr_pwm1_auto_point2_temp.dev_attr.attr,
> +	&sensor_dev_attr_pwm1_auto_point3_pwm.dev_attr.attr,
> +	&sensor_dev_attr_pwm1_auto_point3_temp.dev_attr.attr,
> +	&sensor_dev_attr_pwm1_auto_point4_pwm.dev_attr.attr,
> +	&sensor_dev_attr_pwm1_auto_point4_temp.dev_attr.attr,
> +	&sensor_dev_attr_pwm1_auto_point5_pwm.dev_attr.attr,
> +	&sensor_dev_attr_pwm1_auto_point5_temp.dev_attr.attr,
> +	&sensor_dev_attr_pwm1_auto_point6_pwm.dev_attr.attr,
> +	&sensor_dev_attr_pwm1_auto_point6_temp.dev_attr.attr,
> +	NULL
> +};
> +
> +static const struct attribute_group gsc_hwmon_group = {
> +	.attrs = gsc_hwmon_attributes,
> +};
> +__ATTRIBUTE_GROUPS(gsc_hwmon);
> +
> +static int
> +gsc_hwmon_read(struct device *dev, enum hwmon_sensor_types type, u32 attr,
> +	       int channel, long *val)
> +{
> +	struct gsc_hwmon_data *hwmon = dev_get_drvdata(dev);
> +	const struct gsc_hwmon_channel *ch;
> +	int sz, ret;
> +	long tmp;
> +	u8 buf[3];
> +
> +	switch (type) {
> +	case hwmon_in:
> +		ch = hwmon->in_ch[channel];
> +		break;
> +	case hwmon_temp:
> +		ch = hwmon->temp_ch[channel];
> +		break;
> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +
> +	sz = (ch->mode == mode_voltage) ? 3 : 2;
> +	ret = regmap_bulk_read(hwmon->regmap, ch->reg, buf, sz);
> +	if (ret)
> +		return ret;
> +
> +	tmp = 0;
> +	while (sz-- > 0)
> +		tmp |= (buf[sz] << (8 * sz));
> +
> +	switch (ch->mode) {
> +	case mode_temperature:
> +		if (tmp > 0x8000)
> +			tmp -= 0xffff;
> +		break;
> +	case mode_voltage_raw:
> +		tmp = clamp_val(tmp, 0, BIT(GSC_HWMON_RESOLUTION));
> +		/* scale based on ref voltage and ADC resolution */
> +		tmp *= GSC_HWMON_VREF;
> +		tmp >>= GSC_HWMON_RESOLUTION;
> +		/* scale based on optional voltage divider */
> +		if (ch->vdiv[0] && ch->vdiv[1]) {
> +			tmp *= (ch->vdiv[0] + ch->vdiv[1]);
> +			tmp /= ch->vdiv[1];
> +		}
> +		/* adjust by uV offset */
> +		tmp += ch->mvoffset;
> +		break;
> +	case mode_voltage:
> +		/* no adjustment needed */
> +		break;
> +	}
> +
> +	*val = tmp;
> +
> +	return 0;
> +}
> +
> +static int
> +gsc_hwmon_read_string(struct device *dev, enum hwmon_sensor_types type,
> +		      u32 attr, int channel, const char **buf)
> +{
> +	struct gsc_hwmon_data *hwmon = dev_get_drvdata(dev);
> +
> +	switch (type) {
> +	case hwmon_in:
> +		*buf = hwmon->in_ch[channel]->name;
> +		break;
> +	case hwmon_temp:
> +		*buf = hwmon->temp_ch[channel]->name;
> +		break;
> +	default:
> +		return -ENOTSUPP;
> +	}
> +
> +	return 0;
> +}
> +
> +static umode_t
> +gsc_hwmon_is_visible(const void *_data, enum hwmon_sensor_types type, u32 attr,
> +		     int ch)
> +{
> +	return 0444;
> +}
> +
> +static const struct hwmon_ops gsc_hwmon_ops = {
> +	.is_visible = gsc_hwmon_is_visible,
> +	.read = gsc_hwmon_read,
> +	.read_string = gsc_hwmon_read_string,
> +};
> +
> +static struct gsc_hwmon_platform_data *
> +gsc_hwmon_get_devtree_pdata(struct device *dev)
> +{
> +	struct gsc_hwmon_platform_data *pdata;
> +	struct gsc_hwmon_channel *ch;
> +	struct fwnode_handle *child;
> +	struct device_node *fan;
> +	int nchannels;
> +
> +	nchannels = device_get_child_node_count(dev);
> +	if (nchannels == 0)
> +		return ERR_PTR(-ENODEV);
> +
> +	pdata = devm_kzalloc(dev,
> +			     sizeof(*pdata) + nchannels * sizeof(*ch),
> +			     GFP_KERNEL);
> +	if (!pdata)
> +		return ERR_PTR(-ENOMEM);
> +	ch = (struct gsc_hwmon_channel *)(pdata + 1);
> +	pdata->channels = ch;
> +	pdata->nchannels = nchannels;
> +
> +	/* fan controller base address */
> +	fan = of_find_compatible_node(dev->parent->of_node, NULL, "gw,gsc-fan");
> +	if (fan && of_property_read_u32(fan, "reg", &pdata->fan_base)) {
> +		dev_err(dev, "fan node without base\n");
> +		return ERR_PTR(-EINVAL);
> +	}
> +
> +	/* allocate structures for channels and count instances of each type */
> +	device_for_each_child_node(dev, child) {
> +		if (fwnode_property_read_string(child, "label", &ch->name)) {
> +			dev_err(dev, "channel without label\n");
> +			fwnode_handle_put(child);
> +			return ERR_PTR(-EINVAL);
> +		}
> +		if (fwnode_property_read_u32(child, "reg", &ch->reg)) {
> +			dev_err(dev, "channel without reg\n");
> +			fwnode_handle_put(child);
> +			return ERR_PTR(-EINVAL);
> +		}
> +		if (fwnode_property_read_u32(child, "gw,mode", &ch->mode)) {
> +			dev_err(dev, "channel without mode\n");
> +			fwnode_handle_put(child);
> +			return ERR_PTR(-EINVAL);
> +		}
> +		if (ch->mode > mode_max) {
> +			dev_err(dev, "invalid channel mode\n");
> +			fwnode_handle_put(child);
> +			return ERR_PTR(-EINVAL);
> +		}
> +
> +		if (!fwnode_property_read_u32(child,
> +					      "gw,voltage-offset-microvolt",
> +					      &ch->mvoffset))
> +			ch->mvoffset /= 1000;
> +		fwnode_property_read_u32_array(child,
> +					       "gw,voltage-divider-ohms",
> +					       ch->vdiv, ARRAY_SIZE(ch->vdiv));
> +		ch++;
> +	}
> +
> +	return pdata;
> +}
> +
> +static int gsc_hwmon_probe(struct platform_device *pdev)
> +{
> +	struct gsc_dev *gsc = dev_get_drvdata(pdev->dev.parent);
> +	struct device *dev = &pdev->dev;
> +	struct device *hwmon_dev;
> +	struct gsc_hwmon_platform_data *pdata = dev_get_platdata(dev);
> +	struct gsc_hwmon_data *hwmon;
> +	const struct attribute_group **groups;
> +	int i, i_in, i_temp;
> +
> +	if (!pdata) {
> +		pdata = gsc_hwmon_get_devtree_pdata(dev);
> +		if (IS_ERR(pdata))
> +			return PTR_ERR(pdata);
> +	}
> +
> +	hwmon = devm_kzalloc(dev, sizeof(*hwmon), GFP_KERNEL);
> +	if (!hwmon)
> +		return -ENOMEM;
> +	hwmon->gsc = gsc;
> +	hwmon->pdata = pdata;
> +
> +	hwmon->regmap = devm_regmap_init(dev, &gsc->bus,
> +					 gsc->i2c_hwmon,
> +					 &gsc_hwmon_regmap_config);
> +	if (IS_ERR(hwmon->regmap))
> +		return PTR_ERR(hwmon->regmap);
> +
> +	for (i = 0, i_in = 0, i_temp = 0; i < hwmon->pdata->nchannels; i++) {
> +		const struct gsc_hwmon_channel *ch = &pdata->channels[i];
> +
> +		switch (ch->mode) {
> +		case mode_temperature:
> +			if (i_temp == GSC_HWMON_MAX_TEMP_CH) {
> +				dev_err(gsc->dev, "too many temp channels\n");
> +				return -EINVAL;
> +			}
> +			hwmon->temp_ch[i_temp] = ch;
> +			hwmon->temp_config[i_temp] = HWMON_T_INPUT |
> +						     HWMON_T_LABEL;
> +			i_temp++;
> +			break;
> +		case mode_voltage:
> +		case mode_voltage_raw:
> +			if (i_in == GSC_HWMON_MAX_IN_CH) {
> +				dev_err(gsc->dev, "too many input channels\n");
> +				return -EINVAL;
> +			}
> +			hwmon->in_ch[i_in] = ch;
> +			hwmon->in_config[i_in] =
> +				HWMON_I_INPUT | HWMON_I_LABEL;
> +			i_in++;
> +			break;
> +		default:
> +			dev_err(gsc->dev, "invalid mode: %d\n", ch->mode);
> +			return -EINVAL;
> +		}
> +	}
> +
> +	/* setup config structures */
> +	hwmon->chip.ops = &gsc_hwmon_ops;
> +	hwmon->chip.info = hwmon->info;
> +	hwmon->info[0] = &hwmon->temp_info;
> +	hwmon->info[1] = &hwmon->in_info;
> +	hwmon->temp_info.type = hwmon_temp;
> +	hwmon->temp_info.config = hwmon->temp_config;
> +	hwmon->in_info.type = hwmon_in;
> +	hwmon->in_info.config = hwmon->in_config;
> +
> +	groups = pdata->fan_base ? gsc_hwmon_groups : NULL;
> +	hwmon_dev = devm_hwmon_device_register_with_info(dev,
> +							 KBUILD_MODNAME, hwmon,
> +							 &hwmon->chip, groups);
> +	return PTR_ERR_OR_ZERO(hwmon_dev);
> +}
> +
> +static const struct of_device_id gsc_hwmon_of_match[] = {
> +	{ .compatible = "gw,gsc-adc", },
> +	{}
> +};
> +
> +static struct platform_driver gsc_hwmon_driver = {
> +	.driver = {
> +		.name = "gsc-hwmon",
> +		.of_match_table = gsc_hwmon_of_match,
> +	},
> +	.probe = gsc_hwmon_probe,
> +};
> +
> +module_platform_driver(gsc_hwmon_driver);
> +
> +MODULE_AUTHOR("Tim Harvey <tharvey@xxxxxxxxxxxxx>");
> +MODULE_DESCRIPTION("GSC hardware monitor driver");
> +MODULE_LICENSE("GPL v2");
> diff --git a/include/linux/platform_data/gsc_hwmon.h b/include/linux/platform_data/gsc_hwmon.h
> new file mode 100644
> index 00000000..ec1611a
> --- /dev/null
> +++ b/include/linux/platform_data/gsc_hwmon.h
> @@ -0,0 +1,44 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _GSC_HWMON_H
> +#define _GSC_HWMON_H
> +
> +enum gsc_hwmon_mode {
> +	mode_temperature,
> +	mode_voltage,
> +	mode_voltage_raw,
> +	mode_max,
> +};
> +
> +/**
> + * struct gsc_hwmon_channel - configuration parameters
> + * @reg:  I2C register offset
> + * @mode: channel mode
> + * @name: channel name
> + * @mvoffset: voltage offset
> + * @vdiv: voltage divider array (2 resistor values in milli-ohms)
> + */
> +struct gsc_hwmon_channel {
> +	unsigned int reg;
> +	unsigned int mode;
> +	const char *name;
> +	unsigned int mvoffset;
> +	unsigned int vdiv[2];
> +};
> +
> +/**
> + * struct gsc_hwmon_platform_data - platform data for gsc_hwmon driver
> + * @channels:	pointer to array of gsc_hwmon_channel structures
> + *		describing channels
> + * @nchannels:	number of elements in @channels array
> + * @vreference: voltage reference (mV)
> + * @resolution: ADC bit resolution
> + * @fan_base: register base for FAN controller
> + */
> +struct gsc_hwmon_platform_data {
> +	const struct gsc_hwmon_channel *channels;
> +	int nchannels;
> +	unsigned int resolution;
> +	unsigned int vreference;
> +	unsigned int fan_base;
> +};
> +#endif