diff options
Diffstat (limited to 'Documentation/devicetree/bindings/i2c/i2c-ocores.txt')
| -rw-r--r-- | Documentation/devicetree/bindings/i2c/i2c-ocores.txt | 18 |
1 files changed, 16 insertions, 2 deletions
diff --git a/Documentation/devicetree/bindings/i2c/i2c-ocores.txt b/Documentation/devicetree/bindings/i2c/i2c-ocores.txt index 1637c298a1b..5bef3adf2c3 100644 --- a/Documentation/devicetree/bindings/i2c/i2c-ocores.txt +++ b/Documentation/devicetree/bindings/i2c/i2c-ocores.txt @@ -4,15 +4,29 @@ 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 +- opencores,ip-clock-frequency: frequency of the controller clock in Hz; + see the note below - #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 +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 opencores,ip-clock-frequency is not, + 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 opencores,ip-clock-frequency is present it specifies i2c controller + clock frequency. clock-frequency property specifies i2c bus frequency. + Example: i2c0: ocores@a0000000 { @@ -21,7 +35,7 @@ Example: compatible = "opencores,i2c-ocores"; reg = <0xa0000000 0x8>; interrupts = <10>; - clock-frequency = <20000000>; + opencores,ip-clock-frequency = <20000000>; reg-shift = <0>; /* 8 bit registers */ reg-io-width = <1>; /* 8 bit read/write */ |