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regmap: fix documentation to match code

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The regmap binding talks about one thing, which is register
endianess, and it gets almost every aspect of it wrong.

This replaces the current text of the file with a version
that makes more sense and that matches what we implement
now.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: a06c488da0 ("regmap: Add explict native endian flag to DT bindings")
Fixes: 275876e208 ("regmap: Add the DT binding documentation for endianness")
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Arnd Bergmann 2016-03-17 18:23:40 +01:00 committed by Mark Brown
parent d25263d917
commit 2596e07a3e
1 changed files with 20 additions and 41 deletions
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61
Documentation/devicetree/bindings/regmap/regmap.txt
View file

@ -1,50 +1,29 @@
Device-Tree binding for regmap
The endianness mode of CPU & Device scenarios:
Index Device Endianness properties
---------------------------------------------------
1 BE 'big-endian'
2 LE 'little-endian'
3 Native 'native-endian'
For one device driver, which will run in different scenarios above
on different SoCs using the devicetree, we need one way to simplify
this.
Devicetree binding for regmap
Optional properties:
- {big,little,native}-endian: these are boolean properties, if absent
then the implementation will choose a default based on the device
being controlled. These properties are for register values and all
the buffers only. Native endian means that the CPU and device have
the same endianness.
little-endian,
big-endian,
native-endian: See common-properties.txt for a definition
Note:
Regmap defaults to little-endian register access on MMIO based
devices, this is by far the most common setting. On CPU
architectures that typically run big-endian operating systems
(e.g. PowerPC), registers can be defined as big-endian and must
be marked that way in the devicetree.
On SoCs that can be operated in both big-endian and little-endian
modes, with a single hardware switch controlling both the endianess
of the CPU and a byteswap for MMIO registers (e.g. many Broadcom MIPS
chips), "native-endian" is used to allow using the same device tree
blob in both cases.
Examples:
Scenario 1 : CPU in LE mode & device in LE mode.
Scenario 1 : a register set in big-endian mode.
dev: dev@40031000 {
compatible = "name";
compatible = "syscon";
reg = <0x40031000 0x1000>;
...
};
Scenario 2 : CPU in LE mode & device in BE mode.
dev: dev@40031000 {
compatible = "name";
reg = <0x40031000 0x1000>;
...
big-endian;
};
Scenario 3 : CPU in BE mode & device in BE mode.
dev: dev@40031000 {
compatible = "name";
reg = <0x40031000 0x1000>;
...
};
Scenario 4 : CPU in BE mode & device in LE mode.
dev: dev@40031000 {
compatible = "name";
reg = <0x40031000 0x1000>;
...
little-endian;
};