i2c: axxia: Add I2C driver for AXM55xx

Add I2C bus driver for the controller found in the LSI Axxia family SoCs. The
driver implements 10-bit addressing and SMBus transfer modes via emulation
(including SMBus block data read).
Signed-off-by: Anders Berg <anders.berg@avagotech.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Documentation/devicetree/bindings/i2c/i2c-axxia.txt

+LSI Axxia I2C
+
+Required properties :
+- compatible : Must be "lsi,api2c"
+- reg : Offset and length of the register set for the device
+- interrupts : the interrupt specifier
+- #address-cells : Must be <1>;
+- #size-cells : Must be <0>;
+- clock-names : Must contain "i2c".
+- clocks: Must contain an entry for each name in clock-names. See the common
+  clock bindings.
+
+Optional properties :
+- clock-frequency : Desired I2C bus clock frequency in Hz. If not specified,
+  the default 100 kHz frequency will be used. As only Normal and Fast modes
+  are supported, possible values are 100000 and 400000.
+
+Example :
+
+i2c@02010084000 {
+	compatible = "lsi,api2c";
+	device_type = "i2c";
+	#address-cells = <1>;
+	#size-cells = <0>;
+	reg = <0x20 0x10084000 0x00 0x1000>;
+	interrupts = <0 19 4>;
+	clocks = <&clk_per>;
+	clock-names = "i2c";
+	clock-frequency = <400000>;
+};

drivers/i2c/busses/Kconfig

@@ -337,6 +337,17 @@ config I2C_AU1550
 	  This driver can also be built as a module.  If so, the module
 	  will be called i2c-au1550.
 
+config I2C_AXXIA
+	tristate "Axxia I2C controller"
+	depends on ARCH_AXXIA || COMPILE_TEST
+	default ARCH_AXXIA
+	help
+	  Say yes if you want to support the I2C bus on Axxia platforms.
+
+	  Please note that this controller is limited to transfers of maximum
+	  255 bytes in length. Any attempt to to a larger transfer will return
+	  an error.
+
 config I2C_BCM2835
 	tristate "Broadcom BCM2835 I2C controller"
 	depends on ARCH_BCM2835

drivers/i2c/busses/Makefile

@@ -31,6 +31,7 @@ obj-$(CONFIG_I2C_POWERMAC)	+= i2c-powermac.o
 # Embedded system I2C/SMBus host controller drivers
 obj-$(CONFIG_I2C_AT91)		+= i2c-at91.o
 obj-$(CONFIG_I2C_AU1550)	+= i2c-au1550.o
+obj-$(CONFIG_I2C_AXXIA)		+= i2c-axxia.o
 obj-$(CONFIG_I2C_BCM2835)	+= i2c-bcm2835.o
 obj-$(CONFIG_I2C_BLACKFIN_TWI)	+= i2c-bfin-twi.o
 obj-$(CONFIG_I2C_CADENCE)	+= i2c-cadence.o