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authorMax Filippov <jcmvbkbc@gmail.com>2015-02-02 18:28:12 +0300
committerWolfram Sang <wsa@the-dreams.de>2015-02-05 22:29:15 +0100
commit3a33a85401ecdb0e2c01ea86d9e36a5711ce01d4 (patch)
treef94aad5c7f9ee69d07a81db4e3fcaa1214202eb8 /Documentation
parent8c340f6090e365ce5bac02eed07c1de3aa83f735 (diff)
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i2c: ocores: fix clock-frequency binding usage
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. Introduce new attribute, opencores,ip-clock-frequency, that specifies i2c controller clock frequency and make clock-frequency attribute compatible with other i2c drivers. Maintain backwards compatibility in case opencores,ip-clock-frequency attribute is missing. Signed-off-by: Max Filippov <jcmvbkbc@gmail.com> Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/devicetree/bindings/i2c/i2c-ocores.txt18
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 1637c298a1b3..5bef3adf2c35 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 */