hwmon: (aspeed-g6-pwm-tacho): Support for ASPEED g6 PWM/Fan tach

The driver support two functions: PWM and Tachometer. The PWM feature can
handle up to 16 output ports, while the Tachometer can monitor to up to 16
input ports as well. This driver implements them by exposing two kernel
subsystems: PWM and HWMON. The PWM subsystem can be utilized alongside
existing drivers for controlling elements such as fans (pwm-fan.c),
beepers (pwm-beeper.c) and so on. Through the HWMON subsystem, the driver
provides sysfs interfaces for fan.

Signed-off-by: Billy Tsai <billy_tsai@aspeedtech.com>
Link: https://lore.kernel.org/r/20240221104025.1306227-4-billy_tsai@aspeedtech.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Author: billy-tsai

Documentation/hwmon/aspeed-g6-pwm-tach.rst

@@ -0,0 +1,26 @@
+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+Kernel driver aspeed-g6-pwm-tach
+=================================
+
+Supported chips:
+	ASPEED AST2600
+
+Authors:
+	<billy_tsai@aspeedtech.com>
+
+Description:
+------------
+This driver implements support for ASPEED AST2600 Fan Tacho controller.
+The 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.
+fanX_div	rw	Fan divisor: Supported value are power of 4 (1, 4, 16
+                        64, ... 4194304)
+                        The larger divisor, the less rpm accuracy and the less
+                        affected by fan signal glitch.
+=============== ======= ======================================================

Documentation/hwmon/index.rst

@@ -44,6 +44,7 @@ Hardware Monitoring Kernel Drivers
    aquacomputer_d5next
    asb100
    asc7621
+   aspeed-g6-pwm-tach
    aspeed-pwm-tacho
    asus_ec_sensors
    asus_rog_ryujin

drivers/hwmon/Kconfig

@@ -422,6 +422,17 @@ config SENSORS_ASPEED
 	  This driver can also be built as a module. If so, the module
 	  will be called aspeed_pwm_tacho.
 
+config SENSORS_ASPEED_G6
+	tristate "ASPEED g6 PWM and Fan tach driver"
+	depends on ARCH_ASPEED || COMPILE_TEST
+	depends on PWM
+	help
+	  This driver provides support for ASPEED G6 PWM and Fan Tach
+	  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

@@ -55,6 +55,7 @@ obj-$(CONFIG_SENSORS_ARM_SCPI)	+= scpi-hwmon.o
 obj-$(CONFIG_SENSORS_AS370)	+= as370-hwmon.o
 obj-$(CONFIG_SENSORS_ASC7621)	+= asc7621.o
 obj-$(CONFIG_SENSORS_ASPEED)	+= aspeed-pwm-tacho.o
+obj-$(CONFIG_SENSORS_ASPEED_G6) += aspeed-g6-pwm-tach.o
 obj-$(CONFIG_SENSORS_ASUS_ROG_RYUJIN)	+= asus_rog_ryujin.o
 obj-$(CONFIG_SENSORS_ATXP1)	+= atxp1.o
 obj-$(CONFIG_SENSORS_AXI_FAN_CONTROL) += axi-fan-control.o