rtc: rv3028: add new driver

upstream commit e6e7376.

Add a driver for the MicroCrystal RV-3028. It is a SMT Real-Time Clock
Module that incorporates an integrated CMOS circuit together with an XTAL.
It has an i2c interface.

The driver handles date/time, alarms, trickle charging, timestamping,
frequency offset correction, EEPROM and NVRAM.

Signed-off-by: Alexandre Belloni <[email protected]>

Author: alexandrebelloni

Documentation/devicetree/bindings/rtc/rtc.txt

@@ -0,0 +1,69 @@
+Generic device tree bindings for Real Time Clock devices
+========================================================
+
+This document describes generic bindings which can be used to describe Real Time
+Clock devices in a device tree.
+
+Required properties
+-------------------
+
+- compatible : name of RTC device following generic names recommended practice.
+
+For other required properties e.g. to describe register sets,
+clocks, etc. check the binding documentation of the specific driver.
+
+Optional properties
+-------------------
+
+- start-year : if provided, the default hardware range supported by the RTC is
+               shifted so the first usable year is the specified one.
+
+The following properties may not be supported by all drivers. However, if a
+driver wants to support one of the below features, it should adapt the bindings
+below.
+- trickle-resistor-ohms :   Selected resistor for trickle charger. Should be given
+                            if trickle charger should be enabled
+- trickle-diode-disable :   Do not use internal trickle charger diode Should be
+                            given if internal trickle charger diode should be
+                            disabled
+- wakeup-source :           Enables wake up of host system on alarm
+- quartz-load-femtofarads : The capacitive load of the quartz(x-tal),
+                            expressed in femto Farad (fF).
+                            The default value shall be listed (if optional),
+                            and likewise all valid values.
+
+Trivial RTCs
+------------
+
+This is a list of trivial RTC devices that have simple device tree
+bindings, consisting only of a compatible field, an address and
+possibly an interrupt line.
+
+
+Compatible		Vendor / Chip
+==========		=============
+abracon,abb5zes3	AB-RTCMC-32.768kHz-B5ZE-S3: Real Time Clock/Calendar Module with I2C Interface
+dallas,ds1374		I2C, 32-Bit Binary Counter Watchdog RTC with Trickle Charger and Reset Input/Output
+dallas,ds1672		Dallas DS1672 Real-time Clock
+dallas,ds3232		Extremely Accurate I²C RTC with Integrated Crystal and SRAM
+epson,rx8010		I2C-BUS INTERFACE REAL TIME CLOCK MODULE
+epson,rx8581		I2C-BUS INTERFACE REAL TIME CLOCK MODULE
+emmicro,em3027		EM Microelectronic EM3027 Real-time Clock
+isil,isl1208		Intersil ISL1208 Low Power RTC with Battery Backed SRAM
+isil,isl1218		Intersil ISL1218 Low Power RTC with Battery Backed SRAM
+isil,isl12022		Intersil ISL12022 Real-time Clock
+microcrystal,rv3028	Real Time Clock Module with I2C-Bus
+microcrystal,rv3029	Real Time Clock Module with I2C-Bus
+microcrystal,rv8523	Real Time Clock
+nxp,pcf2127		Real-time clock
+nxp,pcf2129		Real-time clock
+nxp,pcf8563		Real-time clock/calendar
+pericom,pt7c4338	Real-time Clock Module
+ricoh,r2025sd		I2C bus SERIAL INTERFACE REAL-TIME CLOCK IC
+ricoh,r2221tl		I2C bus SERIAL INTERFACE REAL-TIME CLOCK IC
+ricoh,rs5c372a		I2C bus SERIAL INTERFACE REAL-TIME CLOCK IC
+ricoh,rs5c372b		I2C bus SERIAL INTERFACE REAL-TIME CLOCK IC
+ricoh,rv5c386		I2C bus SERIAL INTERFACE REAL-TIME CLOCK IC
+ricoh,rv5c387a		I2C bus SERIAL INTERFACE REAL-TIME CLOCK IC
+sii,s35390a		2-wire CMOS real-time clock
+whwave,sd3078		I2C bus SERIAL INTERFACE REAL-TIME CLOCK IC

drivers/rtc/Kconfig

@@ -625,6 +625,15 @@ config RTC_DRV_EM3027
 	  This driver can also be built as a module. If so, the module
 	  will be called rtc-em3027.
 
+config RTC_DRV_RV3028
+	tristate "Micro Crystal RV3028"
+	help
+	  If you say yes here you get support for the Micro Crystal
+	  RV3028.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called rtc-rv3028.
+
 config RTC_DRV_RV8803
 	tristate "Micro Crystal RV8803, Epson RX8900"
 	help

drivers/rtc/Makefile

@@ -136,6 +136,7 @@ obj-$(CONFIG_RTC_DRV_RS5C313)	+= rtc-rs5c313.o
 obj-$(CONFIG_RTC_DRV_RS5C348)	+= rtc-rs5c348.o
 obj-$(CONFIG_RTC_DRV_RS5C372)	+= rtc-rs5c372.o
 obj-$(CONFIG_RTC_DRV_RTD119X)	+= rtc-rtd119x.o
+obj-$(CONFIG_RTC_DRV_RV3028)	+= rtc-rv3028.o
 obj-$(CONFIG_RTC_DRV_RV3029C2)	+= rtc-rv3029c2.o
 obj-$(CONFIG_RTC_DRV_RV8803)	+= rtc-rv8803.o
 obj-$(CONFIG_RTC_DRV_RX4581)	+= rtc-rx4581.o