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dt-bindings: Remove Linuxisms from common-properties binding

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We shouldn't reference Linux kernel functions or Linux itself in proper
bindings. It's OK to reference functions in the kernel when explaining
examples, but otherwise we shouldn't reference functions to describe
what the binding means.

Cc: Hsin-Yi Wang <hsinyi@chromium.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Rob Herring <robh@kernel.org>
This commit is contained in:
Stephen Boyd 2019-05-14 13:40:51 -07:00 committed by Rob Herring
parent d698a38814
commit 253a41c6fb
1 changed files with 8 additions and 9 deletions
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17
Documentation/devicetree/bindings/common-properties.txt
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@ -5,30 +5,29 @@ Endianness
---------- ----------
The Devicetree Specification does not define any properties related to hardware The Devicetree Specification does not define any properties related to hardware
byteswapping, but endianness issues show up frequently in porting Linux to byte swapping, but endianness issues show up frequently in porting drivers to
different machine types. This document attempts to provide a consistent different machine types. This document attempts to provide a consistent
way of handling byteswapping across drivers. way of handling byte swapping across drivers.
Optional properties: Optional properties:
- big-endian: Boolean; force big endian register accesses - big-endian: Boolean; force big endian register accesses
unconditionally (e.g. ioread32be/iowrite32be). Use this if you unconditionally (e.g. ioread32be/iowrite32be). Use this if you
know the peripheral always needs to be accessed in BE mode. know the peripheral always needs to be accessed in big endian (BE) mode.
- little-endian: Boolean; force little endian register accesses - little-endian: Boolean; force little endian register accesses
unconditionally (e.g. readl/writel). Use this if you know the unconditionally (e.g. readl/writel). Use this if you know the
peripheral always needs to be accessed in LE mode. peripheral always needs to be accessed in little endian (LE) mode.
- native-endian: Boolean; always use register accesses matched to the - native-endian: Boolean; always use register accesses matched to the
endianness of the kernel binary (e.g. LE vmlinux -> readl/writel, endianness of the kernel binary (e.g. LE vmlinux -> readl/writel,
BE vmlinux -> ioread32be/iowrite32be). In this case no byteswaps BE vmlinux -> ioread32be/iowrite32be). In this case no byte swaps
will ever be performed. Use this if the hardware "self-adjusts" will ever be performed. Use this if the hardware "self-adjusts"
register endianness based on the CPU's configured endianness. register endianness based on the CPU's configured endianness.
If a binding supports these properties, then the binding should also If a binding supports these properties, then the binding should also
specify the default behavior if none of these properties are present. specify the default behavior if none of these properties are present.
In such cases, little-endian is the preferred default, but it is not In such cases, little-endian is the preferred default, but it is not
a requirement. The of_device_is_big_endian() and of_fdt_is_big_endian() a requirement. Some implementations assume that little-endian is
helper functions do assume that little-endian is the default, because the default, because most existing (PCI-based) drivers implicitly
most existing (PCI-based) drivers implicitly default to LE by using default to LE for their MMIO accesses.
readl/writel for MMIO accesses.
Examples: Examples:
Scenario 1 : CPU in LE mode & device in LE mode. Scenario 1 : CPU in LE mode & device in LE mode.