hwmon: add driver for the Microchip LAN966x SoC

Add support for the temperatur sensor and the fan controller on the
Microchip LAN966x SoC. Apparently, an Analog Bits PVT sensor is used
which can measure temperature and process voltages. But only a forumlae
for the temperature sensor is known. Additionally, the SoC support a fan
tacho input as well as a PWM signal to control the fan.
Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20220401214032.3738095-5-michael@walle.cc
[groeck: Added missing reference in Documentation/hwmon/index.rst]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/hwmon/index.rst

@@ -90,6 +90,7 @@ Hardware Monitoring Kernel Drivers
    jc42
    k10temp
    k8temp
+   lan966x
    lineage-pem
    lm25066
    lm63

Documentation/hwmon/lan966x.rst

+.. SPDX-License-Identifier: GPL-2.0
+
+Kernel driver lan966x-hwmon
+===========================
+
+Supported chips:
+
+  * Microchip LAN9668 (sensor in SoC)
+
+    Prefix: 'lan9668-hwmon'
+
+    Datasheet: https://microchip-ung.github.io/lan9668_reginfo
+
+Authors:
+
+	Michael Walle <michael@walle.cc>
+
+Description
+-----------
+
+This driver implements support for the Microchip LAN9668 on-chip
+temperature sensor as well as its fan controller. It provides one
+temperature sensor and one fan controller. The temperature range
+of the sensor is specified from -40 to +125 degrees Celsius and
+its accuracy is +/- 5 degrees Celsius. The fan controller has a
+tacho input and a PWM output with a customizable PWM output
+frequency ranging from ~20Hz to ~650kHz.
+
+No alarms are supported by the SoC.
+
+The driver exports temperature values, fan tacho input and PWM
+settings via the following sysfs files:
+
+**temp1_input**
+
+**fan1_input**
+
+**pwm1**
+
+**pwm1_freq**

drivers/hwmon/Kconfig

@@ -819,6 +819,18 @@ config SENSORS_POWR1220
 	  This driver can also be built as a module. If so, the module
 	  will be called powr1220.
 
+config SENSORS_LAN966X
+	tristate "Microchip LAN966x Hardware Monitoring"
+	depends on SOC_LAN966 || COMPILE_TEST
+	select REGMAP
+	select POLYNOMIAL
+	help
+	  If you say yes here you get support for temperature monitoring
+	  on the Microchip LAN966x SoC.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called lan966x-hwmon.
+
 config SENSORS_LINEAGE
 	tristate "Lineage Compact Power Line Power Entry Module"
 	depends on I2C

drivers/hwmon/Makefile

@@ -100,6 +100,7 @@ obj-$(CONFIG_SENSORS_IT87)	+= it87.o
 obj-$(CONFIG_SENSORS_JC42)	+= jc42.o
 obj-$(CONFIG_SENSORS_K8TEMP)	+= k8temp.o
 obj-$(CONFIG_SENSORS_K10TEMP)	+= k10temp.o
+obj-$(CONFIG_SENSORS_LAN966X)	+= lan966x-hwmon.o
 obj-$(CONFIG_SENSORS_LINEAGE)	+= lineage-pem.o
 obj-$(CONFIG_SENSORS_LOCHNAGAR)	+= lochnagar-hwmon.o
 obj-$(CONFIG_SENSORS_LM63)	+= lm63.o