1 files changed, 39 insertions, 3 deletions

diff --git a/Documentation/devicetree/bindings/i2c/i2c-ocores.txt b/Documentation/devicetree/bindings/i2c/i2c-ocores.txt
index 1637c298a1b3..17bef9a34e50 100644
--- a/Documentation/devicetree/bindings/i2c/i2c-ocores.txt
+++ b/Documentation/devicetree/bindings/i2c/i2c-ocores.txt
@@ -4,24 +4,60 @@ Required properties:
 - compatible      : "opencores,i2c-ocores" or "aeroflexgaisler,i2cmst"
 - reg             : bus address start and address range size of device
 - interrupts      : interrupt number
-- clock-frequency : frequency of bus clock in Hz
+- clocks          : handle to the controller clock; see the note below.
+                    Mutually exclusive with opencores,ip-clock-frequency
+- opencores,ip-clock-frequency: frequency of the controller clock in Hz;
+                    see the note below. Mutually exclusive with clocks
 - #address-cells  : should be <1>
 - #size-cells     : should be <0>
 
 Optional properties:
+- clock-frequency : frequency of bus clock in Hz; see the note below.
+                    Defaults to 100 KHz when the property is not specified
 - reg-shift       : device register offsets are shifted by this value
 - reg-io-width    : io register width in bytes (1, 2 or 4)
 - regstep         : deprecated, use reg-shift above
 
-Example:
+Note
+clock-frequency property is meant to control the bus frequency for i2c bus
+drivers, but it was incorrectly used to specify i2c controller input clock
+frequency. So the following rules are set to fix this situation:
+- if clock-frequency is present and neither opencores,ip-clock-frequency nor
+  clocks are, then clock-frequency specifies i2c controller clock frequency.
+  This is to keep backwards compatibility with setups using old DTB. i2c bus
+  frequency is fixed at 100 KHz.
+- if clocks is present it specifies i2c controller clock. clock-frequency
+  property specifies i2c bus frequency.
+- if opencores,ip-clock-frequency is present it specifies i2c controller
+  clock frequency. clock-frequency property specifies i2c bus frequency.
 
+Examples:
+
+        i2c0: ocores@a0000000 {
+                #address-cells = <1>;
+                #size-cells = <0>;
+                compatible = "opencores,i2c-ocores";
+                reg = <0xa0000000 0x8>;
+                interrupts = <10>;
+                opencores,ip-clock-frequency = <20000000>;
+
+                reg-shift = <0>;        /* 8 bit registers */
+                reg-io-width = <1>;     /* 8 bit read/write */
+
+                dummy@60 {
+                        compatible = "dummy";
+                        reg = <0x60>;
+                };
+        };
+or
         i2c0: ocores@a0000000 {
                 #address-cells = <1>;
                 #size-cells = <0>;
                 compatible = "opencores,i2c-ocores";
                 reg = <0xa0000000 0x8>;
                 interrupts = <10>;
-                clock-frequency = <20000000>;
+                clocks = <&osc>;
+                clock-frequency = <400000>; /* i2c bus frequency 400 KHz */
 
                 reg-shift = <0>;        /* 8 bit registers */
                 reg-io-width = <1>;     /* 8 bit read/write */