hwmon: Add support for Lineage Compact Power Line PEM devices

This patch adds support for hardware monitoring of Lineage Compact Power Line
Power Entry Modules.
Reviewed-by: Tom Grennan <tom.grennan@ericsson.com>
Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>

Documentation/hwmon/lineage-pem

+Kernel driver lineage-pem
+=========================
+
+Supported devices:
+  * Lineage Compact Power Line Power Entry Modules
+    Prefix: 'lineage-pem'
+    Addresses scanned: -
+    Documentation:
+        http://www.lineagepower.com/oem/pdf/CPLI2C.pdf
+
+Author: Guenter Roeck <guenter.roeck@ericsson.com>
+
+
+Description
+-----------
+
+This driver supports various Lineage Compact Power Line DC/DC and AC/DC
+converters such as CP1800, CP2000AC, CP2000DC, CP2100DC, and others.
+
+Lineage CPL power entry modules are nominally PMBus compliant. However, most
+standard PMBus commands are not supported. Specifically, all hardware monitoring
+and status reporting commands are non-standard. For this reason, a standard
+PMBus driver can not be used.
+
+
+Usage Notes
+-----------
+
+This driver does not probe for Lineage CPL devices, since there is no register
+which can be safely used to identify the chip. You will have to instantiate
+the devices explicitly.
+
+Example: the following will load the driver for a Lineage PEM at address 0x40
+on I2C bus #1:
+$ modprobe lineage-pem
+$ echo lineage-pem 0x40 > /sys/bus/i2c/devices/i2c-1/new_device
+
+All Lineage CPL power entry modules have a built-in I2C bus master selector
+(PCA9541). To ensure device access, this driver should only be used as client
+driver to the pca9541 I2C master selector driver.
+
+
+Sysfs entries
+-------------
+
+All Lineage CPL devices report output voltage and device temperature as well as
+alarms for output voltage, temperature, input voltage, input current, input power,
+and fan status.
+
+Input voltage, input current, input power, and fan speed measurement is only
+supported on newer devices. The driver detects if those attributes are supported,
+and only creates respective sysfs entries if they are.
+
+in1_input		Output voltage (mV)
+in1_min_alarm		Output undervoltage alarm
+in1_max_alarm		Output overvoltage alarm
+in1_crit		Output voltage critical alarm
+
+in2_input		Input voltage (mV, optional)
+in2_alarm		Input voltage alarm
+
+curr1_input		Input current (mA, optional)
+curr1_alarm		Input overcurrent alarm
+
+power1_input		Input power (uW, optional)
+power1_alarm		Input power alarm
+
+fan1_input		Fan 1 speed (rpm, optional)
+fan2_input		Fan 2 speed (rpm, optional)
+fan3_input		Fan 3 speed (rpm, optional)
+
+temp1_input
+temp1_max
+temp1_crit
+temp1_alarm
+temp1_crit_alarm
+temp1_fault

drivers/hwmon/Kconfig

@@ -467,6 +467,17 @@ config SENSORS_JC42
 	  This driver can also be built as a module.  If so, the module
 	  will be called jc42.
 
+config SENSORS_LINEAGE
+	tristate "Lineage Compact Power Line Power Entry Module"
+	depends on I2C && EXPERIMENTAL
+	help
+	  If you say yes here you get support for the Lineage Compact Power Line
+	  series of DC/DC and AC/DC converters such as CP1800, CP2000AC,
+	  CP2000DC, CP2725, and others.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called lineage-pem.
+
 config SENSORS_LM63
 	tristate "National Semiconductor LM63 and LM64"
 	depends on I2C

drivers/hwmon/Makefile

@@ -62,6 +62,7 @@ obj-$(CONFIG_SENSORS_JC42)	+= jc42.o
 obj-$(CONFIG_SENSORS_JZ4740)	+= jz4740-hwmon.o
 obj-$(CONFIG_SENSORS_K8TEMP)	+= k8temp.o
 obj-$(CONFIG_SENSORS_K10TEMP)	+= k10temp.o
+obj-$(CONFIG_SENSORS_LINEAGE)	+= lineage-pem.o
 obj-$(CONFIG_SENSORS_LIS3LV02D) += lis3lv02d.o hp_accel.o
 obj-$(CONFIG_SENSORS_LIS3_SPI)	+= lis3lv02d.o lis3lv02d_spi.o
 obj-$(CONFIG_SENSORS_LIS3_I2C)	+= lis3lv02d.o lis3lv02d_i2c.o