[Skiboot] [PATCH 2/2] Document the device-tree entries of I2C.

[Neelesh Gupta]

Signed-off-by: Neelesh Gupta <neelegup at linux.vnet.ibm.com>
---
 doc/device-tree/ibm,opal/i2cm.txt |   51 +++++++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)
 create mode 100644 doc/device-tree/ibm,opal/i2cm.txt

diff --git a/doc/device-tree/ibm,opal/i2cm.txt b/doc/device-tree/ibm,opal/i2cm.txt
new file mode 100644
index 0000000..7c4044f
--- /dev/null
+++ b/doc/device-tree/ibm,opal/i2cm.txt
@@ -0,0 +1,51 @@
+I2C master
+----------
+
+There are multiple i2c masters present on the CEC hardware, the P8 systems host
+the i2c masters on their processor and centaur (memory buffer) chips. Each i2c
+master has multiple ports/busses where the physical bus connects to the i2c
+slave devices.
+
+i2cm proerties:
+- reg: xscom base address of the controller and length of memory mapped region.
+- chip-engine#: engine/master number on a given processor or centaur chip.
+- compatible: "ibm,power8-i2cm", "ibm,centaur-i2cm"
+- clock-frequency: Nest frequency for calculating the bit-rate-divisor that
+  decides the operating frequency of the i2c bus.
+
+i2c-bus properties:
+- reg: Port number the bus is connected to
+- bus-frequency: Operating frequency of the bus (typically 400 KHz)
+- compatible: "ibm,power8-i2c-port", "ibm,opal-i2c"
+- ibm,port-name: Firmware provided unique name to identify a specific bus
+
+Example:
+
+i2cm at a0004 {
+	reg = <0xa0004 0x20>;
+	chip-engine# = <0x0>;
+	compatible = "ibm,centaur-i2cm";
+	clock-frequency = <0x23c34600>;
+	#address-cells = <0x1>;
+	phandle = <0x1000003f>;
+	#size-cells = <0x0>;
+	linux,phandle = <0x1000003f>;
+
+	i2c-bus at 0 {
+		reg = <0x0>;
+		bus-frequency = <0x61a80>;
+		compatible = "ibm,power8-i2c-port", "ibm,opal-i2c";
+		ibm,port-name = "cen_80000001_e0p0";
+		#address-cells = <0x1>;
+		phandle = <0x10000040>;
+		#size-cells = <0x0>;
+		linux,phandle = <0x10000040>;
+
+		eeprom at 52 {
+			reg = <0x52>;
+			label = "dimm-spd-8";
+			phandle = <0x10000041>;
+			linux,phandle = <0x10000041>;
+		}
+	}
+}