diff --git a/Documentation/devicetree/bindings/i2c/trivial-devices.txt b/Documentation/devicetree/bindings/i2c/trivial-devices.txt
index 1416c6a0d2cd..833fb9f133d3 100644
--- a/Documentation/devicetree/bindings/i2c/trivial-devices.txt
+++ b/Documentation/devicetree/bindings/i2c/trivial-devices.txt
@@ -122,6 +122,8 @@ microchip,mcp4662-502	Microchip 8-bit Dual I2C Digital Potentiometer with NV Mem
 microchip,mcp4662-103	Microchip 8-bit Dual I2C Digital Potentiometer with NV Memory (10k)
 microchip,mcp4662-503	Microchip 8-bit Dual I2C Digital Potentiometer with NV Memory (50k)
 microchip,mcp4662-104	Microchip 8-bit Dual I2C Digital Potentiometer with NV Memory (100k)
+microchip,tc654		PWM Fan Speed Controller With Fan Fault Detection
+microchip,tc655		PWM Fan Speed Controller With Fan Fault Detection
 national,lm63		Temperature sensor with integrated fan control
 national,lm75		I2C TEMP SENSOR
 national,lm80		Serial Interface ACPI-Compatible Microprocessor System Hardware Monitor
diff --git a/Documentation/hwmon/tc654 b/Documentation/hwmon/tc654
new file mode 100644
index 000000000000..91a2843f5f98
--- /dev/null
+++ b/Documentation/hwmon/tc654
@@ -0,0 +1,31 @@
+Kernel driver tc654
+===================
+
+Supported chips:
+  * Microship TC654 and TC655
+    Prefix: 'tc654'
+    Datasheet: http://ww1.microchip.com/downloads/en/DeviceDoc/20001734C.pdf
+
+Authors:
+        Chris Packham <chris.packham@alliedtelesis.co.nz>
+        Masahiko Iwamoto <iwamoto@allied-telesis.co.jp>
+
+Description
+-----------
+This driver implements support for the Microchip TC654 and TC655.
+
+The TC654 uses the 2-wire interface compatible with the SMBUS 2.0
+specification. The TC654 has two (2) inputs for measuring fan RPM and
+one (1) PWM output which can be used for fan control.
+
+Configuration Notes
+-------------------
+Ordinarily the pwm1_mode ABI is used for controlling the pwm output
+mode.  However, for this chip the output is always pwm, and the
+pwm1_mode determines if the pwm output is controlled via the pwm1 value
+or via the Vin analog input.
+
+
+Setting pwm1_mode to 1 will cause the pwm output to be driven based on
+the pwm1 value. Setting pwm1_mode to 0 will cause the pwm output to be
+driven based on the Vin input.
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 45cef3d2c75c..8681bc65cde5 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -907,6 +907,17 @@ config SENSORS_MCP3021
 	  This driver can also be built as a module.  If so, the module
 	  will be called mcp3021.
 
+config SENSORS_TC654
+	tristate "Microchip TC654/TC655 and compatibles"
+	depends on I2C
+	help
+	  If you say yes here you get support for TC654 and TC655.
+	  The TC654 and TC655 are PWM mode fan speed controllers with
+	  FanSense technology for use with brushless DC fans.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called tc654.
+
 config SENSORS_MENF21BMC_HWMON
 	tristate "MEN 14F021P00 BMC Hardware Monitoring"
 	depends on MFD_MENF21BMC
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index aecf4ba17460..c651f0f1d047 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -122,6 +122,7 @@ obj-$(CONFIG_SENSORS_MAX6697)	+= max6697.o
 obj-$(CONFIG_SENSORS_MAX31790)	+= max31790.o
 obj-$(CONFIG_SENSORS_MC13783_ADC)+= mc13783-adc.o
 obj-$(CONFIG_SENSORS_MCP3021)	+= mcp3021.o
+obj-$(CONFIG_SENSORS_TC654)	+= tc654.o
 obj-$(CONFIG_SENSORS_MENF21BMC_HWMON) += menf21bmc_hwmon.o
 obj-$(CONFIG_SENSORS_NCT6683)	+= nct6683.o
 obj-$(CONFIG_SENSORS_NCT6775)	+= nct6775.o
diff --git a/drivers/hwmon/tc654.c b/drivers/hwmon/tc654.c
new file mode 100644
index 000000000000..04485f6d6983
--- /dev/null
+++ b/drivers/hwmon/tc654.c
@@ -0,0 +1,514 @@
+/*
+ * tc654.c - Linux kernel modules for fan speed controller
+ *
+ * Copyright (C) 2016 Allied Telesis Labs NZ
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/bitops.h>
+#include <linux/err.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/jiffies.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/util_macros.h>
+
+enum tc654_regs {
+	TC654_REG_RPM1 = 0x00,	/* RPM Output 1 */
+	TC654_REG_RPM2 = 0x01,	/* RPM Output 2 */
+	TC654_REG_FAN_FAULT1 = 0x02,	/* Fan Fault 1 Threshold */
+	TC654_REG_FAN_FAULT2 = 0x03,	/* Fan Fault 2 Threshold */
+	TC654_REG_CONFIG = 0x04,	/* Configuration */
+	TC654_REG_STATUS = 0x05,	/* Status */
+	TC654_REG_DUTY_CYCLE = 0x06,	/* Fan Speed Duty Cycle */
+	TC654_REG_MFR_ID = 0x07,	/* Manufacturer Identification */
+	TC654_REG_VER_ID = 0x08,	/* Version Identification */
+};
+
+/* Macros to easily index the registers */
+#define TC654_REG_RPM(idx)		(TC654_REG_RPM1 + (idx))
+#define TC654_REG_FAN_FAULT(idx)	(TC654_REG_FAN_FAULT1 + (idx))
+
+/* Config register bits */
+#define TC654_REG_CONFIG_RES		BIT(6)	/* Resolution Selection */
+#define TC654_REG_CONFIG_DUTYC		BIT(5)	/* Duty Cycle Control */
+#define TC654_REG_CONFIG_SDM		BIT(0)	/* Shutdown Mode */
+
+/* Status register bits */
+#define TC654_REG_STATUS_F2F		BIT(1)	/* Fan 2 Fault */
+#define TC654_REG_STATUS_F1F		BIT(0)	/* Fan 1 Fault */
+
+/* RPM resolution for RPM Output registers */
+#define TC654_HIGH_RPM_RESOLUTION	25	/* 25 RPM resolution */
+#define TC654_LOW_RPM_RESOLUTION	50	/* 50 RPM resolution */
+
+/* Convert to the fan fault RPM threshold from register value */
+#define TC654_FAN_FAULT_FROM_REG(val)	((val) * 50)	/* 50 RPM resolution */
+
+/* Convert to register value from the fan fault RPM threshold */
+#define TC654_FAN_FAULT_TO_REG(val)	(((val) / 50) & 0xff)
+
+/* Register data is read (and cached) at most once per second. */
+#define TC654_UPDATE_INTERVAL		HZ
+
+struct tc654_data {
+	struct i2c_client *client;
+
+	/* update mutex */
+	struct mutex update_lock;
+
+	/* tc654 register cache */
+	bool valid;
+	unsigned long last_updated;	/* in jiffies */
+
+	u8 rpm_output[2];	/* The fan RPM data for fans 1 and 2 is then
+				 * written to registers RPM1 and RPM2
+				 */
+	u8 fan_fault[2];	/* The Fan Fault Threshold Registers are used to
+				 * set the fan fault threshold levels for fan 1
+				 * and fan 2
+				 */
+	u8 config;	/* The Configuration Register is an 8-bit read/
+			 * writable multi-function control register
+			 *   7: Fan Fault Clear
+			 *      1 = Clear Fan Fault
+			 *      0 = Normal Operation (default)
+			 *   6: Resolution Selection for RPM Output Registers
+			 *      RPM Output Registers (RPM1 and RPM2) will be
+			 *      set for
+			 *      1 = 25 RPM (9-bit) resolution
+			 *      0 = 50 RPM (8-bit) resolution (default)
+			 *   5: Duty Cycle Control Method
+			 *      The V OUT duty cycle will be controlled via
+			 *      1 = the SMBus interface.
+			 *      0 = via the V IN analog input pin. (default)
+			 * 4,3: Fan 2 Pulses Per Rotation
+			 *      00 = 1
+			 *      01 = 2 (default)
+			 *      10 = 4
+			 *      11 = 8
+			 * 2,1: Fan 1 Pulses Per Rotation
+			 *      00 = 1
+			 *      01 = 2 (default)
+			 *      10 = 4
+			 *      11 = 8
+			 *   0: Shutdown Mode
+			 *      1 = Shutdown mode.
+			 *      0 = Normal operation. (default)
+			 */
+	u8 status;	/* The Status register provides all the information
+			 * about what is going on within the TC654/TC655
+			 * devices.
+			 * 7,6: Unimplemented, Read as '0'
+			 *   5: Over-Temperature Fault Condition
+			 *      1 = Over-Temperature condition has occurred
+			 *      0 = Normal operation. V IN is less than 2.6V
+			 *   4: RPM2 Counter Overflow
+			 *      1 = Fault condition
+			 *      0 = Normal operation
+			 *   3: RPM1 Counter Overflow
+			 *      1 = Fault condition
+			 *      0 = Normal operation
+			 *   2: V IN Input Status
+			 *      1 = V IN is open
+			 *      0 = Normal operation. voltage present at V IN
+			 *   1: Fan 2 Fault
+			 *      1 = Fault condition
+			 *      0 = Normal operation
+			 *   0: Fan 1 Fault
+			 *      1 = Fault condition
+			 *      0 = Normal operation
+			 */
+	u8 duty_cycle;	/* The DUTY_CYCLE register is a 4-bit read/
+			 * writable register used to control the duty
+			 * cycle of the V OUT output.
+			 */
+};
+
+/* helper to grab and cache data, at most one time per second */
+static struct tc654_data *tc654_update_client(struct device *dev)
+{
+	struct tc654_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+	int ret = 0;
+
+	mutex_lock(&data->update_lock);
+	if (time_before(jiffies, data->last_updated + TC654_UPDATE_INTERVAL) &&
+	    likely(data->valid))
+		goto out;
+
+	ret = i2c_smbus_read_byte_data(client, TC654_REG_RPM(0));
+	if (ret < 0)
+		goto out;
+	data->rpm_output[0] = ret;
+
+	ret = i2c_smbus_read_byte_data(client, TC654_REG_RPM(1));
+	if (ret < 0)
+		goto out;
+	data->rpm_output[1] = ret;
+
+	ret = i2c_smbus_read_byte_data(client, TC654_REG_FAN_FAULT(0));
+	if (ret < 0)
+		goto out;
+	data->fan_fault[0] = ret;
+
+	ret = i2c_smbus_read_byte_data(client, TC654_REG_FAN_FAULT(1));
+	if (ret < 0)
+		goto out;
+	data->fan_fault[1] = ret;
+
+	ret = i2c_smbus_read_byte_data(client, TC654_REG_CONFIG);
+	if (ret < 0)
+		goto out;
+	data->config = ret;
+
+	ret = i2c_smbus_read_byte_data(client, TC654_REG_STATUS);
+	if (ret < 0)
+		goto out;
+	data->status = ret;
+
+	ret = i2c_smbus_read_byte_data(client, TC654_REG_DUTY_CYCLE);
+	if (ret < 0)
+		goto out;
+	data->duty_cycle = ret & 0x0f;
+
+	data->last_updated = jiffies;
+	data->valid = true;
+out:
+	mutex_unlock(&data->update_lock);
+
+	if (ret < 0)		/* upon error, encode it in return value */
+		data = ERR_PTR(ret);
+
+	return data;
+}
+
+/*
+ * sysfs attributes
+ */
+
+static ssize_t show_fan(struct device *dev, struct device_attribute *da,
+			char *buf)
+{
+	int nr = to_sensor_dev_attr(da)->index;
+	struct tc654_data *data = tc654_update_client(dev);
+	int val;
+
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+
+	if (data->config & TC654_REG_CONFIG_RES)
+		val = data->rpm_output[nr] * TC654_HIGH_RPM_RESOLUTION;
+	else
+		val = data->rpm_output[nr] * TC654_LOW_RPM_RESOLUTION;
+
+	return sprintf(buf, "%d\n", val);
+}
+
+static ssize_t show_fan_min(struct device *dev, struct device_attribute *da,
+			    char *buf)
+{
+	int nr = to_sensor_dev_attr(da)->index;
+	struct tc654_data *data = tc654_update_client(dev);
+
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+
+	return sprintf(buf, "%d\n",
+		       TC654_FAN_FAULT_FROM_REG(data->fan_fault[nr]));
+}
+
+static ssize_t set_fan_min(struct device *dev, struct device_attribute *da,
+			   const char *buf, size_t count)
+{
+	int nr = to_sensor_dev_attr(da)->index;
+	struct tc654_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+	unsigned long val;
+	int ret;
+
+	if (kstrtoul(buf, 10, &val))
+		return -EINVAL;
+
+	val = clamp_val(val, 0, 12750);
+
+	mutex_lock(&data->update_lock);
+
+	data->fan_fault[nr] = TC654_FAN_FAULT_TO_REG(val);
+	ret = i2c_smbus_write_byte_data(client, TC654_REG_FAN_FAULT(nr),
+					data->fan_fault[nr]);
+
+	mutex_unlock(&data->update_lock);
+	return ret < 0 ? ret : count;
+}
+
+static ssize_t show_fan_alarm(struct device *dev, struct device_attribute *da,
+			      char *buf)
+{
+	int nr = to_sensor_dev_attr(da)->index;
+	struct tc654_data *data = tc654_update_client(dev);
+	int val;
+
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+
+	if (nr == 0)
+		val = !!(data->status & TC654_REG_STATUS_F1F);
+	else
+		val = !!(data->status & TC654_REG_STATUS_F2F);
+
+	return sprintf(buf, "%d\n", val);
+}
+
+static const u8 TC654_FAN_PULSE_SHIFT[] = { 1, 3 };
+
+static ssize_t show_fan_pulses(struct device *dev, struct device_attribute *da,
+			      char *buf)
+{
+	int nr = to_sensor_dev_attr(da)->index;
+	struct tc654_data *data = tc654_update_client(dev);
+	u8 val;
+
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+
+	val = BIT((data->config >> TC654_FAN_PULSE_SHIFT[nr]) & 0x03);
+	return sprintf(buf, "%d\n", val);
+}
+
+static ssize_t set_fan_pulses(struct device *dev, struct device_attribute *da,
+			     const char *buf, size_t count)
+{
+	int nr = to_sensor_dev_attr(da)->index;
+	struct tc654_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+	u8 config;
+	unsigned long val;
+	int ret;
+
+	if (kstrtoul(buf, 10, &val))
+		return -EINVAL;
+
+	switch (val) {
+	case 1:
+		config = 0;
+		break;
+	case 2:
+		config = 1;
+		break;
+	case 4:
+		config = 2;
+		break;
+	case 8:
+		config = 3;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	mutex_lock(&data->update_lock);
+
+	data->config &= ~(0x03 << TC654_FAN_PULSE_SHIFT[nr]);
+	data->config |= (config << TC654_FAN_PULSE_SHIFT[nr]);
+	ret = i2c_smbus_write_byte_data(client, TC654_REG_CONFIG, data->config);
+
+	mutex_unlock(&data->update_lock);
+	return ret < 0 ? ret : count;
+}
+
+static ssize_t show_pwm_mode(struct device *dev,
+			     struct device_attribute *da, char *buf)
+{
+	struct tc654_data *data = tc654_update_client(dev);
+
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+
+	return sprintf(buf, "%d\n", !!(data->config & TC654_REG_CONFIG_DUTYC));
+}
+
+static ssize_t set_pwm_mode(struct device *dev,
+			    struct device_attribute *da,
+			    const char *buf, size_t count)
+{
+	struct tc654_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+	unsigned long val;
+	int ret;
+
+	if (kstrtoul(buf, 10, &val))
+		return -EINVAL;
+
+	if (val != 0 && val != 1)
+		return -EINVAL;
+
+	mutex_lock(&data->update_lock);
+
+	if (val)
+		data->config |= TC654_REG_CONFIG_DUTYC;
+	else
+		data->config &= ~TC654_REG_CONFIG_DUTYC;
+
+	ret = i2c_smbus_write_byte_data(client, TC654_REG_CONFIG, data->config);
+
+	mutex_unlock(&data->update_lock);
+	return ret < 0 ? ret : count;
+}
+
+static const int tc654_pwm_map[16] = { 77,  88, 102, 112, 124, 136, 148, 160,
+				      172, 184, 196, 207, 219, 231, 243, 255};
+
+static ssize_t show_pwm(struct device *dev, struct device_attribute *da,
+			       char *buf)
+{
+	struct tc654_data *data = tc654_update_client(dev);
+	int pwm;
+
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+
+	if (data->config & TC654_REG_CONFIG_SDM)
+		pwm = 0;
+	else
+		pwm = tc654_pwm_map[data->duty_cycle];
+
+	return sprintf(buf, "%d\n", pwm);
+}
+
+static ssize_t set_pwm(struct device *dev, struct device_attribute *da,
+			      const char *buf, size_t count)
+{
+	struct tc654_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+	unsigned long val;
+	int ret;
+
+	if (kstrtoul(buf, 10, &val))
+		return -EINVAL;
+	if (val > 255)
+		return -EINVAL;
+
+	mutex_lock(&data->update_lock);
+
+	if (val == 0)
+		data->config |= TC654_REG_CONFIG_SDM;
+	else
+		data->config &= ~TC654_REG_CONFIG_SDM;
+
+	data->duty_cycle = find_closest(val, tc654_pwm_map,
+					ARRAY_SIZE(tc654_pwm_map));
+
+	ret = i2c_smbus_write_byte_data(client, TC654_REG_CONFIG, data->config);
+	if (ret < 0)
+		goto out;
+
+	ret = i2c_smbus_write_byte_data(client, TC654_REG_DUTY_CYCLE,
+				  data->duty_cycle);
+
+out:
+	mutex_unlock(&data->update_lock);
+	return ret < 0 ? ret : count;
+}
+
+static SENSOR_DEVICE_ATTR(fan1_input, S_IRUGO, show_fan, NULL, 0);
+static SENSOR_DEVICE_ATTR(fan2_input, S_IRUGO, show_fan, NULL, 1);
+static SENSOR_DEVICE_ATTR(fan1_min, S_IWUSR | S_IRUGO, show_fan_min,
+			  set_fan_min, 0);
+static SENSOR_DEVICE_ATTR(fan2_min, S_IWUSR | S_IRUGO, show_fan_min,
+			  set_fan_min, 1);
+static SENSOR_DEVICE_ATTR(fan1_alarm, S_IRUGO, show_fan_alarm, NULL, 0);
+static SENSOR_DEVICE_ATTR(fan2_alarm, S_IRUGO, show_fan_alarm, NULL, 1);
+static SENSOR_DEVICE_ATTR(fan1_pulses, S_IWUSR | S_IRUGO, show_fan_pulses,
+			  set_fan_pulses, 0);
+static SENSOR_DEVICE_ATTR(fan2_pulses, S_IWUSR | S_IRUGO, show_fan_pulses,
+			  set_fan_pulses, 1);
+static SENSOR_DEVICE_ATTR(pwm1_mode, S_IWUSR | S_IRUGO,
+			  show_pwm_mode, set_pwm_mode, 0);
+static SENSOR_DEVICE_ATTR(pwm1, S_IWUSR | S_IRUGO, show_pwm,
+			  set_pwm, 0);
+
+/* Driver data */
+static struct attribute *tc654_attrs[] = {
+	&sensor_dev_attr_fan1_input.dev_attr.attr,
+	&sensor_dev_attr_fan2_input.dev_attr.attr,
+	&sensor_dev_attr_fan1_min.dev_attr.attr,
+	&sensor_dev_attr_fan2_min.dev_attr.attr,
+	&sensor_dev_attr_fan1_alarm.dev_attr.attr,
+	&sensor_dev_attr_fan2_alarm.dev_attr.attr,
+	&sensor_dev_attr_fan1_pulses.dev_attr.attr,
+	&sensor_dev_attr_fan2_pulses.dev_attr.attr,
+	&sensor_dev_attr_pwm1_mode.dev_attr.attr,
+	&sensor_dev_attr_pwm1.dev_attr.attr,
+	NULL
+};
+
+ATTRIBUTE_GROUPS(tc654);
+
+/*
+ * device probe and removal
+ */
+
+static int tc654_probe(struct i2c_client *client,
+		       const struct i2c_device_id *id)
+{
+	struct device *dev = &client->dev;
+	struct tc654_data *data;
+	struct device *hwmon_dev;
+	int ret;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_BYTE_DATA))
+		return -ENODEV;
+
+	data = devm_kzalloc(dev, sizeof(struct tc654_data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->client = client;
+	mutex_init(&data->update_lock);
+
+	ret = i2c_smbus_read_byte_data(client, TC654_REG_CONFIG);
+	if (ret < 0)
+		return ret;
+
+	data->config = ret;
+
+	hwmon_dev =
+	    devm_hwmon_device_register_with_groups(dev, client->name, data,
+						   tc654_groups);
+	return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+static const struct i2c_device_id tc654_id[] = {
+	{"tc654", 0},
+	{"tc655", 0},
+	{}
+};
+
+MODULE_DEVICE_TABLE(i2c, tc654_id);
+
+static struct i2c_driver tc654_driver = {
+	.driver = {
+		   .name = "tc654",
+		   },
+	.probe = tc654_probe,
+	.id_table = tc654_id,
+};
+
+module_i2c_driver(tc654_driver);
+
+MODULE_AUTHOR("Allied Telesis Labs");
+MODULE_DESCRIPTION("Microchip TC654/TC655 driver");
+MODULE_LICENSE("GPL");
