Merge tag 'ib-mfd-hwmon-v5.8' into hwmon-next

Immutable branch between MFD and HWMON due for the v5.8 merge window

12 files changed, 1074 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/mfd/gateworks-gsc.yaml b/Documentation/devicetree/bindings/mfd/gateworks-gsc.yaml
new file mode 100644
index 000000000000..487a8445722e
--- /dev/null
+++ b/Documentation/devicetree/bindings/mfd/gateworks-gsc.yaml
@@ -0,0 +1,196 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/mfd/gateworks-gsc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Gateworks System Controller
+
+description: |
+  The Gateworks System Controller (GSC) is a device present across various
+  Gateworks product families that provides a set of system related features
+  such as the following (refer to the board hardware user manuals to see what
+  features are present)
+   - Watchdog Timer
+   - GPIO
+   - Pushbutton controller
+   - Hardware monitor with ADC's for temperature and voltage rails and
+     fan controller
+
+maintainers:
+  - Tim Harvey <tharvey@gateworks.com>
+  - Robert Jones <rjones@gateworks.com>
+
+properties:
+  $nodename:
+    pattern: "gsc@[0-9a-f]{1,2}"
+  compatible:
+    const: gw,gsc
+
+  reg:
+    description: I2C device address
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  interrupt-controller: true
+
+  "#interrupt-cells":
+    const: 1
+
+  "#address-cells":
+    const: 1
+
+  "#size-cells":
+    const: 0
+
+  adc:
+    type: object
+    description: Optional hardware monitoring module
+
+    properties:
+      compatible:
+        const: gw,gsc-adc
+
+      "#address-cells":
+        const: 1
+
+      "#size-cells":
+        const: 0
+
+    patternProperties:
+      "^channel@[0-9]+$":
+        type: object
+        description: |
+          Properties for a single ADC which can report cooked values
+          (i.e. temperature sensor based on thermister), raw values
+          (i.e. voltage rail with a pre-scaling resistor divider).
+
+        properties:
+          reg:
+            description: Register of the ADC
+            maxItems: 1
+
+          label:
+            description: Name of the ADC input
+
+          gw,mode:
+            description: |
+              conversion mode:
+                0 - temperature, in C*10
+                1 - pre-scaled voltage value
+                2 - scaled voltage based on an optional resistor divider
+                    and optional offset
+            $ref: /schemas/types.yaml#/definitions/uint32
+            enum: [0, 1, 2]
+
+          gw,voltage-divider-ohms:
+            description: Values of resistors for divider on raw ADC input
+            maxItems: 2
+            items:
+             minimum: 1000
+             maximum: 1000000
+
+          gw,voltage-offset-microvolt:
+            description: |
+              A positive voltage offset to apply to a raw ADC
+              (i.e. to compensate for a diode drop).
+            minimum: 0
+            maximum: 1000000
+
+        required:
+          - gw,mode
+          - reg
+          - label
+
+    required:
+      - compatible
+      - "#address-cells"
+      - "#size-cells"
+
+patternProperties:
+  "^fan-controller@[0-9a-f]+$":
+    type: object
+    description: Optional fan controller
+
+    properties:
+      compatible:
+        const: gw,gsc-fan
+
+      "#address-cells":
+        const: 1
+
+      "#size-cells":
+        const: 0
+
+      reg:
+        description: The fan controller base address
+        maxItems: 1
+
+    required:
+      - compatible
+      - reg
+      - "#address-cells"
+      - "#size-cells"
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - interrupt-controller
+  - "#interrupt-cells"
+  - "#address-cells"
+  - "#size-cells"
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        gsc@20 {
+            compatible = "gw,gsc";
+            reg = <0x20>;
+            interrupt-parent = <&gpio1>;
+            interrupts = <4 GPIO_ACTIVE_LOW>;
+            interrupt-controller;
+            #interrupt-cells = <1>;
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            adc {
+                compatible = "gw,gsc-adc";
+                #address-cells = <1>;
+                #size-cells = <0>;
+
+                channel@0 { /* A0: Board Temperature */
+                    reg = <0x00>;
+                    label = "temp";
+                    gw,mode = <0>;
+                };
+
+                channel@2 { /* A1: Input Voltage (raw ADC) */
+                    reg = <0x02>;
+                    label = "vdd_vin";
+                    gw,mode = <1>;
+                    gw,voltage-divider-ohms = <22100 1000>;
+                    gw,voltage-offset-microvolt = <800000>;
+                };
+
+                channel@b { /* A2: Battery voltage */
+                    reg = <0x0b>;
+                    label = "vdd_bat";
+                    gw,mode = <1>;
+                };
+            };
+
+            fan-controller@2c {
+                #address-cells = <1>;
+                #size-cells = <0>;
+                compatible = "gw,gsc-fan";
+                reg = <0x2c>;
+            };
+        };
+    };
diff --git a/Documentation/hwmon/gsc-hwmon.rst b/Documentation/hwmon/gsc-hwmon.rst
new file mode 100644
index 000000000000..ffac392a7129
--- /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@gateworks.com>
+
+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 fb51c7ce8b27..e463fa9a219d 100644
--- a/Documentation/hwmon/index.rst
+++ b/Documentation/hwmon/index.rst
@@ -61,6 +61,7 @@ Hardware Monitoring Kernel Drivers
    ftsteutates
    g760a
    g762
+   gsc-hwmon
    gl518sm
    hih6130
    ibmaem
diff --git a/MAINTAINERS b/MAINTAINERS
index 2b1591875abf..bd6f9b6f55e3 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7035,6 +7035,17 @@ F:	kernel/futex.c
 F:	tools/perf/bench/futex*
 F:	tools/testing/selftests/futex/
 
+GATEWORKS SYSTEM CONTROLLER (GSC) DRIVER
+M:	Tim Harvey <tharvey@gateworks.com>
+M:	Robert Jones <rjones@gateworks.com>
+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
+
 GASKET DRIVER FRAMEWORK
 M:	Rob Springer <rspringer@google.com>
 M:	Todd Poynor <toddpoynor@google.com>
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 2362be5a5b11..3ae303d6c12b 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -533,6 +533,15 @@ 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 318f89dc7133..892174f18f6b 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -75,6 +75,7 @@ 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 000000000000..2137bc65829d
--- /dev/null
+++ b/drivers/hwmon/gsc-hwmon.c
@@ -0,0 +1,390 @@
+// 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 struct regmap_bus gsc_hwmon_regmap_bus = {
+	.reg_read = gsc_read,
+	.reg_write = gsc_write,
+};
+
+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_hwmon_regmap_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@gateworks.com>");
+MODULE_DESCRIPTION("GSC hardware monitor driver");
+MODULE_LICENSE("GPL v2");
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 0a59249198d3..05448e78e5b8 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -407,6 +407,21 @@ config MFD_EXYNOS_LPASS
 	  Select this option to enable support for Samsung Exynos Low Power
 	  Audio Subsystem.
 
+config MFD_GATEWORKS_GSC
+	tristate "Gateworks System Controller"
+	depends on (I2C && OF)
+	select MFD_CORE
+	select REGMAP_I2C
+	select REGMAP_IRQ
+	help
+	  Enable support for the Gateworks System Controller (GSC) found
+	  on Gateworks Single Board Computers supporting system functions
+	  such as push-button monitor, multiple ADC's for voltage and
+	  temperature monitoring, fan controller and watchdog monitor.
+	  This driver provides common support for accessing the device.
+	  Additional drivers must be enabled in order to use the
+	  functionality of the device.
+
 config MFD_MC13XXX
 	tristate
 	depends on (SPI_MASTER || I2C)
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index f935d10cbf0f..ed433aed7010 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -15,6 +15,7 @@ obj-$(CONFIG_MFD_BCM590XX)	+= bcm590xx.o
 obj-$(CONFIG_MFD_BD9571MWV)	+= bd9571mwv.o
 obj-$(CONFIG_MFD_CROS_EC_DEV)	+= cros_ec_dev.o
 obj-$(CONFIG_MFD_EXYNOS_LPASS)	+= exynos-lpass.o
+obj-$(CONFIG_MFD_GATEWORKS_GSC)	+= gateworks-gsc.o
 
 obj-$(CONFIG_HTC_PASIC3)	+= htc-pasic3.o
 obj-$(CONFIG_HTC_I2CPLD)	+= htc-i2cpld.o
diff --git a/drivers/mfd/gateworks-gsc.c b/drivers/mfd/gateworks-gsc.c
new file mode 100644
index 000000000000..576da62fbb0c
--- /dev/null
+++ b/drivers/mfd/gateworks-gsc.c
@@ -0,0 +1,277 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * The Gateworks System Controller (GSC) is a multi-function
+ * device designed for use in Gateworks Single Board Computers.
+ * The control interface is I2C, with an interrupt. The device supports
+ * system functions such as push-button monitoring, multiple ADC's for
+ * voltage and temperature monitoring, fan controller and watchdog monitor.
+ *
+ * Copyright (C) 2020 Gateworks Corporation
+ */
+
+#include <linux/device.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/mfd/gsc.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#include <asm/unaligned.h>
+
+/*
+ * The GSC suffers from an errata where occasionally during
+ * ADC cycles the chip can NAK I2C transactions. To ensure we have reliable
+ * register access we place retries around register access.
+ */
+#define I2C_RETRIES	3
+
+int gsc_write(void *context, unsigned int reg, unsigned int val)
+{
+	struct i2c_client *client = context;
+	int retry, ret;
+
+	for (retry = 0; retry < I2C_RETRIES; retry++) {
+		ret = i2c_smbus_write_byte_data(client, reg, val);
+		/*
+		 * -EAGAIN returned when the i2c host controller is busy
+		 * -EIO returned when i2c device is busy
+		 */
+		if (ret != -EAGAIN && ret != -EIO)
+			break;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(gsc_write);
+
+int gsc_read(void *context, unsigned int reg, unsigned int *val)
+{
+	struct i2c_client *client = context;
+	int retry, ret;
+
+	for (retry = 0; retry < I2C_RETRIES; retry++) {
+		ret = i2c_smbus_read_byte_data(client, reg);
+		/*
+		 * -EAGAIN returned when the i2c host controller is busy
+		 * -EIO returned when i2c device is busy
+		 */
+		if (ret != -EAGAIN && ret != -EIO)
+			break;
+	}
+	*val = ret & 0xff;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(gsc_read);
+
+/*
+ * gsc_powerdown - API to use GSC to power down board for a specific time
+ *
+ * secs - number of seconds to remain powered off
+ */
+static int gsc_powerdown(struct gsc_dev *gsc, unsigned long secs)
+{
+	int ret;
+	unsigned char regs[4];
+
+	dev_info(&gsc->i2c->dev, "GSC powerdown for %ld seconds\n",
+		 secs);
+
+	put_unaligned_le32(secs, regs);
+	ret = regmap_bulk_write(gsc->regmap, GSC_TIME_ADD, regs, 4);
+	if (ret)
+		return ret;
+
+	ret = regmap_update_bits(gsc->regmap, GSC_CTRL_1,
+				 BIT(GSC_CTRL_1_SLEEP_ADD),
+				 BIT(GSC_CTRL_1_SLEEP_ADD));
+	if (ret)
+		return ret;
+
+	ret = regmap_update_bits(gsc->regmap, GSC_CTRL_1,
+				 BIT(GSC_CTRL_1_SLEEP_ACTIVATE) |
+				 BIT(GSC_CTRL_1_SLEEP_ENABLE),
+				 BIT(GSC_CTRL_1_SLEEP_ACTIVATE) |
+				 BIT(GSC_CTRL_1_SLEEP_ENABLE));
+
+
+	return ret;
+}
+
+static ssize_t gsc_show(struct device *dev, struct device_attribute *attr,
+			char *buf)
+{
+	struct gsc_dev *gsc = dev_get_drvdata(dev);
+	const char *name = attr->attr.name;
+	int rz = 0;
+
+	if (strcasecmp(name, "fw_version") == 0)
+		rz = sprintf(buf, "%d\n", gsc->fwver);
+	else if (strcasecmp(name, "fw_crc") == 0)
+		rz = sprintf(buf, "0x%04x\n", gsc->fwcrc);
+	else
+		dev_err(dev, "invalid command: '%s'\n", name);
+
+	return rz;
+}
+
+static ssize_t gsc_store(struct device *dev, struct device_attribute *attr,
+			 const char *buf, size_t count)
+{
+	struct gsc_dev *gsc = dev_get_drvdata(dev);
+	const char *name = attr->attr.name;
+	long value;
+
+	if (strcasecmp(name, "powerdown") == 0) {
+		if (kstrtol(buf, 0, &value) == 0)
+			gsc_powerdown(gsc, value);
+	} else {
+		dev_err(dev, "invalid command: '%s\n", name);
+	}
+
+	return count;
+}
+
+static struct device_attribute attr_fwver =
+	__ATTR(fw_version, 0440, gsc_show, NULL);
+static struct device_attribute attr_fwcrc =
+	__ATTR(fw_crc, 0440, gsc_show, NULL);
+static struct device_attribute attr_pwrdown =
+	__ATTR(powerdown, 0220, NULL, gsc_store);
+
+static struct attribute *gsc_attrs[] = {
+	&attr_fwver.attr,
+	&attr_fwcrc.attr,
+	&attr_pwrdown.attr,
+	NULL,
+};
+
+static struct attribute_group attr_group = {
+	.attrs = gsc_attrs,
+};
+
+static const struct of_device_id gsc_of_match[] = {
+	{ .compatible = "gw,gsc", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, gsc_of_match);
+
+static struct regmap_bus gsc_regmap_bus = {
+	.reg_read = gsc_read,
+	.reg_write = gsc_write,
+};
+
+static const struct regmap_config gsc_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.cache_type = REGCACHE_NONE,
+	.max_register = GSC_WP,
+};
+
+static const struct regmap_irq gsc_irqs[] = {
+	REGMAP_IRQ_REG(GSC_IRQ_PB, 0, BIT(GSC_IRQ_PB)),
+	REGMAP_IRQ_REG(GSC_IRQ_KEY_ERASED, 0, BIT(GSC_IRQ_KEY_ERASED)),
+	REGMAP_IRQ_REG(GSC_IRQ_EEPROM_WP, 0, BIT(GSC_IRQ_EEPROM_WP)),
+	REGMAP_IRQ_REG(GSC_IRQ_RESV, 0, BIT(GSC_IRQ_RESV)),
+	REGMAP_IRQ_REG(GSC_IRQ_GPIO, 0, BIT(GSC_IRQ_GPIO)),
+	REGMAP_IRQ_REG(GSC_IRQ_TAMPER, 0, BIT(GSC_IRQ_TAMPER)),
+	REGMAP_IRQ_REG(GSC_IRQ_WDT_TIMEOUT, 0, BIT(GSC_IRQ_WDT_TIMEOUT)),
+	REGMAP_IRQ_REG(GSC_IRQ_SWITCH_HOLD, 0, BIT(GSC_IRQ_SWITCH_HOLD)),
+};
+
+static const struct regmap_irq_chip gsc_irq_chip = {
+	.name = "gateworks-gsc",
+	.irqs = gsc_irqs,
+	.num_irqs = ARRAY_SIZE(gsc_irqs),
+	.num_regs = 1,
+	.status_base = GSC_IRQ_STATUS,
+	.mask_base = GSC_IRQ_ENABLE,
+	.mask_invert = true,
+	.ack_base = GSC_IRQ_STATUS,
+	.ack_invert = true,
+};
+
+static int gsc_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct gsc_dev *gsc;
+	struct regmap_irq_chip_data *irq_data;
+	int ret;
+	unsigned int reg;
+
+	gsc = devm_kzalloc(dev, sizeof(*gsc), GFP_KERNEL);
+	if (!gsc)
+		return -ENOMEM;
+
+	gsc->dev = &client->dev;
+	gsc->i2c = client;
+	i2c_set_clientdata(client, gsc);
+
+	gsc->regmap = devm_regmap_init(dev, &gsc_regmap_bus, client,
+				       &gsc_regmap_config);
+	if (IS_ERR(gsc->regmap))
+		return PTR_ERR(gsc->regmap);
+
+	if (regmap_read(gsc->regmap, GSC_FW_VER, &reg))
+		return -EIO;
+	gsc->fwver = reg;
+
+	regmap_read(gsc->regmap, GSC_FW_CRC, &reg);
+	gsc->fwcrc = reg;
+	regmap_read(gsc->regmap, GSC_FW_CRC + 1, &reg);
+	gsc->fwcrc |= reg << 8;
+
+	gsc->i2c_hwmon = devm_i2c_new_dummy_device(dev, client->adapter,
+						   GSC_HWMON);
+	if (IS_ERR(gsc->i2c_hwmon)) {
+		dev_err(dev, "Failed to allocate I2C device for HWMON\n");
+		return PTR_ERR(gsc->i2c_hwmon);
+	}
+
+	ret = devm_regmap_add_irq_chip(dev, gsc->regmap, client->irq,
+				       IRQF_ONESHOT | IRQF_SHARED |
+				       IRQF_TRIGGER_FALLING, 0,
+				       &gsc_irq_chip, &irq_data);
+	if (ret)
+		return ret;
+
+	dev_info(dev, "Gateworks System Controller v%d: fw 0x%04x\n",
+		 gsc->fwver, gsc->fwcrc);
+
+	ret = sysfs_create_group(&dev->kobj, &attr_group);
+	if (ret)
+		dev_err(dev, "failed to create sysfs attrs\n");
+
+	ret = devm_of_platform_populate(dev);
+	if (ret) {
+		sysfs_remove_group(&dev->kobj, &attr_group);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int gsc_remove(struct i2c_client *client)
+{
+	sysfs_remove_group(&client->dev.kobj, &attr_group);
+
+	return 0;
+}
+
+static struct i2c_driver gsc_driver = {
+	.driver = {
+		.name	= "gateworks-gsc",
+		.of_match_table = gsc_of_match,
+	},
+	.probe_new	= gsc_probe,
+	.remove		= gsc_remove,
+};
+module_i2c_driver(gsc_driver);
+
+MODULE_AUTHOR("Tim Harvey <tharvey@gateworks.com>");
+MODULE_DESCRIPTION("I2C Core interface for GSC");
+MODULE_LICENSE("GPL v2");
diff --git a/include/linux/mfd/gsc.h b/include/linux/mfd/gsc.h
new file mode 100644
index 000000000000..6bd639c285b4
--- /dev/null
+++ b/include/linux/mfd/gsc.h
@@ -0,0 +1,76 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2020 Gateworks Corporation
+ */
+#ifndef __LINUX_MFD_GSC_H_
+#define __LINUX_MFD_GSC_H_
+
+#include <linux/regmap.h>
+
+/* Device Addresses */
+#define GSC_MISC	0x20
+#define GSC_UPDATE	0x21
+#define GSC_GPIO	0x23
+#define GSC_HWMON	0x29
+#define GSC_EEPROM0	0x50
+#define GSC_EEPROM1	0x51
+#define GSC_EEPROM2	0x52
+#define GSC_EEPROM3	0x53
+#define GSC_RTC		0x68
+
+/* Register offsets */
+enum {
+	GSC_CTRL_0	= 0x00,
+	GSC_CTRL_1	= 0x01,
+	GSC_TIME	= 0x02,
+	GSC_TIME_ADD	= 0x06,
+	GSC_IRQ_STATUS	= 0x0A,
+	GSC_IRQ_ENABLE	= 0x0B,
+	GSC_FW_CRC	= 0x0C,
+	GSC_FW_VER	= 0x0E,
+	GSC_WP		= 0x0F,
+};
+
+/* Bit definitions */
+#define GSC_CTRL_0_PB_HARD_RESET	0
+#define GSC_CTRL_0_PB_CLEAR_SECURE_KEY	1
+#define GSC_CTRL_0_PB_SOFT_POWER_DOWN	2
+#define GSC_CTRL_0_PB_BOOT_ALTERNATE	3
+#define GSC_CTRL_0_PERFORM_CRC		4
+#define GSC_CTRL_0_TAMPER_DETECT	5
+#define GSC_CTRL_0_SWITCH_HOLD		6
+
+#define GSC_CTRL_1_SLEEP_ENABLE		0
+#define GSC_CTRL_1_SLEEP_ACTIVATE	1
+#define GSC_CTRL_1_SLEEP_ADD		2
+#define GSC_CTRL_1_SLEEP_NOWAKEPB	3
+#define GSC_CTRL_1_WDT_TIME		4
+#define GSC_CTRL_1_WDT_ENABLE		5
+#define GSC_CTRL_1_SWITCH_BOOT_ENABLE	6
+#define GSC_CTRL_1_SWITCH_BOOT_CLEAR	7
+
+#define GSC_IRQ_PB			0
+#define GSC_IRQ_KEY_ERASED		1
+#define GSC_IRQ_EEPROM_WP		2
+#define GSC_IRQ_RESV			3
+#define GSC_IRQ_GPIO			4
+#define GSC_IRQ_TAMPER			5
+#define GSC_IRQ_WDT_TIMEOUT		6
+#define GSC_IRQ_SWITCH_HOLD		7
+
+int gsc_read(void *context, unsigned int reg, unsigned int *val);
+int gsc_write(void *context, unsigned int reg, unsigned int val);
+
+struct gsc_dev {
+	struct device *dev;
+
+	struct i2c_client *i2c;		/* 0x20: interrupt controller, WDT */
+	struct i2c_client *i2c_hwmon;	/* 0x29: hwmon, fan controller */
+
+	struct regmap *regmap;
+
+	unsigned int fwver;
+	unsigned short fwcrc;
+};
+
+#endif /* __LINUX_MFD_GSC_H_ */
diff --git a/include/linux/platform_data/gsc_hwmon.h b/include/linux/platform_data/gsc_hwmon.h
new file mode 100644
index 000000000000..ec1611aff863
--- /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