driver for the hardware monitoring chip in the Zyxel NSA320

new file mode 100644
index 0000000..7b346d4
@@ -0,0 +1,21 @@
+Bindings for the fan / temperature monitor microcontroller used on
+the Zyxel NSA 320 and several subsequent models.
+
+Required properties:
+- compatible	: "zyxel,nsa320-mcu"
+- data-gpios	: The GPIO pin connected to the data line on the MCU
+- clk-gpios	: The GPIO pin connected to the clock line on the MCU
+- act-gpios	: The GPIO pin connected to the active line on the MCU
+
+Example:
+
+	hwmon {
+		compatible = "zyxel,nsa320-mcu";
+		pinctrl-0 = <&pmx_mcu_data &pmx_mcu_clk &pmx_mcu_act>;
+		pinctrl-names = "default";
+
+		data-gpios = <&gpio0 14 GPIO_ACTIVE_HIGH>;
+		clk-gpios = <&gpio0 16 GPIO_ACTIVE_HIGH>;
+		act-gpios = <&gpio0 17 GPIO_ACTIVE_LOW>;
+	};
+

new file mode 100644
index 0000000..fdbd694
@@ -0,0 +1,53 @@
+Kernel driver nsa320_hwmon
+==========================
+
+Supported chips:
+  * Holtek HT46R065 microcontroller with onboard firmware that configures
+	it to act as a hardware monitor.
+    Prefix: 'nsa320'
+    Addresses scanned: none
+    Datasheet: Not available, driver was reverse engineered based upon the
+	Zyxel kernel source
+
+Author:
+  Adam Baker <[email protected]>
+
+Description
+-----------
+
+This chip is known to be used in the Zyxel NSA320 and NSA325 NAS Units and
+also in some variants of the NSA310 but the driver has only been tested
+on the NSA320. In all of these devices it is connected to the same 3 GPIO
+lines which are used to provide chip select, clock and data lines. The
+interface behaves similarly to SPI but at much lower speeds than are normally
+used for SPI.
+
+Following each chip select pulse the chip will generate a single 32 bit word
+that contains 0x55 as a marker to indicate that data is being read correctly,
+followed by an 8 bit fan speed in 100s of RPM and a 16 bit temperature in
+tenths of a degree.
+
+
+sysfs-Interface
+---------------
+
+temp1_input - temperature input
+fan1_input - fan speed
+
+Notes
+-----
+
+The access timings used in the driver are the same as used in the Zyxel
+provided kernel. Testing has shown that if the delay between chip select and
+the first clock pulse is reduced from 100 ms to just under 10ms then the chip
+will not produce any output. If the duration of either phase of the clock
+is reduced from 100 us to less than 15 us then data pulses are likely to be
+read twice corrupting the output. The above analysis is based upon a sample
+of one unit but suggests that the Zyxel provided delay values include a
+reasonable tolerance.
+
+The driver incorporates a limit that it will not check for updated values
+faster than once a second. This is because the hardware takes a relatively long
+time to read the data from the device and when it does it reads both temp and
+fan speed. As the most likely case for two accesses in quick succession is
+to read both of these values avoiding a second read delay is desirable.

index 80a73bf..08fd7f5 100644
@@ -1186,6 +1186,21 @@ config SENSORS_NCT7904
 	  This driver can also be built as a module.  If so, the module
 	  will be called nct7904.
 
+config SENSORS_NSA320
+	tristate "ZyXEL NSA320 and compatible fan speed and temperature sensors"
+	depends on GPIOLIB && OF
+	depends on MACH_KIRKWOOD || COMPILE_TEST
+	help
+	  If you say yes here you get support for hardware monitoring
+	  for the ZyXEL NSA320 Media Server and other compatible devices
+	  (probably the NSA325 and some NSA310 variants).
+
+	  The sensor data is taken from a Holtek HT46R065 microcontroller
+	  connected to GPIO lines.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called nsa320-hwmon.
+
 config SENSORS_PCF8591
 	tristate "Philips PCF8591 ADC/DAC"
 	depends on I2C

index 12a3239..9e22cf7 100644
@@ -124,6 +124,7 @@ obj-$(CONFIG_SENSORS_NCT6683)	+= nct6683.o
 obj-$(CONFIG_SENSORS_NCT6775)	+= nct6775.o
 obj-$(CONFIG_SENSORS_NCT7802)	+= nct7802.o
 obj-$(CONFIG_SENSORS_NCT7904)	+= nct7904.o
+obj-$(CONFIG_SENSORS_NSA320)	+= nsa320-hwmon.o
 obj-$(CONFIG_SENSORS_NTC_THERMISTOR)	+= ntc_thermistor.o
 obj-$(CONFIG_SENSORS_PC87360)	+= pc87360.o
 obj-$(CONFIG_SENSORS_PC87427)	+= pc87427.o

index 24f686d..2a935e9 100644
@@ -193,10 +193,19 @@
 		};
 	};
 
+	hwmon {
+		compatible = "zyxel,nsa320-mcu";
+		pinctrl-0 = <&pmx_mcu_data &pmx_mcu_clk &pmx_mcu_act>;
+		pinctrl-names = "default";
+
+		data-gpios = <&gpio0 14 GPIO_ACTIVE_HIGH>;
+		clk-gpios = <&gpio0 16 GPIO_ACTIVE_HIGH>;
+		act-gpios = <&gpio0 17 GPIO_ACTIVE_LOW>;
+	};
+
 	/* The following pins are currently not assigned to a driver,
 	   some of them should be configured as inputs.
-	pinctrl-0 = <&pmx_mcu_data &pmx_mcu_clk &pmx_mcu_act
-		     &pmx_htp &pmx_vid_b1
+	pinctrl-0 = <&pmx_htp &pmx_vid_b1
 		     &pmx_power_resume_data &pmx_power_resume_clk>; */
 };