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author | Andrew Turner <andrew@FreeBSD.org> | 2016-01-28 20:21:15 +0000 |
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committer | Andrew Turner <andrew@FreeBSD.org> | 2016-01-28 20:21:15 +0000 |
commit | 235ad806ee815395bce54dc1b0ce1c06cd29b44a (patch) | |
tree | 41cbd9055ad0d6dfa04377df1bb51f3c3f3948e2 /Bindings/common-properties.txt | |
parent | da75c2cc5808a45edc76752ba495dcc5dcd4346c (diff) | |
download | src-235ad806ee815395bce54dc1b0ce1c06cd29b44a.tar.gz src-235ad806ee815395bce54dc1b0ce1c06cd29b44a.zip |
Import updated device-tree files from:vendor/device-tree/ianc-afaecb70
git://xenbits.xen.org/people/ianc/device-tree-rebasing.git
@afaecb70e7ebb983c86d5eb45ff952e9af79c462
Notes
Notes:
svn path=/vendor/device-tree/dist/; revision=295011
svn path=/vendor/device-tree/ianc-afaecb70/; revision=295013; tag=vendor/device-tree/ianc-afaecb70
Diffstat (limited to 'Bindings/common-properties.txt')
-rw-r--r-- | Bindings/common-properties.txt | 60 |
1 files changed, 60 insertions, 0 deletions
diff --git a/Bindings/common-properties.txt b/Bindings/common-properties.txt new file mode 100644 index 000000000000..3193979b1d05 --- /dev/null +++ b/Bindings/common-properties.txt @@ -0,0 +1,60 @@ +Common properties + +The ePAPR specification does not define any properties related to hardware +byteswapping, but endianness issues show up frequently in porting Linux to +different machine types. This document attempts to provide a consistent +way of handling byteswapping across drivers. + +Optional properties: + - big-endian: Boolean; force big endian register accesses + unconditionally (e.g. ioread32be/iowrite32be). Use this if you + know the peripheral always needs to be accessed in BE mode. + - little-endian: Boolean; force little endian register accesses + unconditionally (e.g. readl/writel). Use this if you know the + peripheral always needs to be accessed in LE mode. + - native-endian: Boolean; always use register accesses matched to the + endianness of the kernel binary (e.g. LE vmlinux -> readl/writel, + BE vmlinux -> ioread32be/iowrite32be). In this case no byteswaps + will ever be performed. Use this if the hardware "self-adjusts" + register endianness based on the CPU's configured endianness. + +If a binding supports these properties, then the binding should also +specify the default behavior if none of these properties are present. +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() +helper functions do assume that little-endian is the default, because +most existing (PCI-based) drivers implicitly default to LE by using +readl/writel for MMIO accesses. + +Examples: +Scenario 1 : CPU in LE mode & device in LE mode. +dev: dev@40031000 { + compatible = "name"; + reg = <0x40031000 0x1000>; + ... + native-endian; +}; + +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>; + ... + native-endian; +}; + +Scenario 4 : CPU in BE mode & device in LE mode. +dev: dev@40031000 { + compatible = "name"; + reg = <0x40031000 0x1000>; + ... + little-endian; +}; |