drivers: hwmon: Support for ASPEED PWM/Fan tach

The ASPEED AST2400/2500 PWM controller supports 8 PWM output ports.
The ASPEED AST2400/2500 Fan tach controller supports 16 tachometer
inputs.
The device driver matches on the device tree node. The configuration
values are read from the device tree and written to the respective
registers.
The driver provides a sysfs entries through which the user can
configure the duty-cycle value (ranging from 0 to 100 percent) and read
the fan tach rpm value.

Signed-off-by: Jaghathiswari Rankappagounder Natarajan <jaghu@google.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/hwmon/aspeed-pwm-tacho

@@ -0,0 +1,22 @@
+Kernel driver aspeed-pwm-tacho
+==============================
+
+Supported chips:
+	ASPEED AST2400/2500
+
+Authors:
+	<jaghu@google.com>
+
+Description:
+------------
+This driver implements support for ASPEED AST2400/2500 PWM and Fan Tacho
+controller. The PWM controller supports upto 8 PWM outputs. The Fan tacho
+controller supports up to 16 tachometer inputs.
+
+The driver provides the following sensor accesses in sysfs:
+
+fanX_input	ro	provide current fan rotation value in RPM as reported
+			by the fan to the device.
+
+pwmX		rw	get or set PWM fan control value. This is an integer
+			value between 0(off) and 255(full speed).

drivers/hwmon/Kconfig

@@ -341,6 +341,15 @@ config SENSORS_ASB100
 	  This driver can also be built as a module.  If so, the module
 	  will be called asb100.
 
+config SENSORS_ASPEED
+	tristate "ASPEED AST2400/AST2500 PWM and Fan tach driver"
+	help
+	  This driver provides support for ASPEED AST2400/AST2500 PWM
+	  and Fan Tacho controllers.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called aspeed_pwm_tacho.
+
 config SENSORS_ATXP1
 	tristate "Attansic ATXP1 VID controller"
 	depends on I2C

drivers/hwmon/Makefile

@@ -46,6 +46,7 @@ obj-$(CONFIG_SENSORS_ADT7475)	+= adt7475.o
 obj-$(CONFIG_SENSORS_APPLESMC)	+= applesmc.o
 obj-$(CONFIG_SENSORS_ARM_SCPI)	+= scpi-hwmon.o
 obj-$(CONFIG_SENSORS_ASC7621)	+= asc7621.o
+obj-$(CONFIG_SENSORS_ASPEED)	+= aspeed-pwm-tacho.o
 obj-$(CONFIG_SENSORS_ATXP1)	+= atxp1.o
 obj-$(CONFIG_SENSORS_CORETEMP)	+= coretemp.o
 obj-$(CONFIG_SENSORS_DA9052_ADC)+= da9052-hwmon.o