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| -rw-r--r-- | Documentation/devicetree/bindings/mtd/partition.txt | 160 |
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diff --git a/Documentation/devicetree/bindings/mtd/partition.txt b/Documentation/devicetree/bindings/mtd/partition.txt new file mode 100644 index 000000000..4a3969822 --- /dev/null +++ b/Documentation/devicetree/bindings/mtd/partition.txt @@ -0,0 +1,160 @@ +Flash partitions in device tree +=============================== + +Flash devices can be partitioned into one or more functional ranges (e.g. "boot +code", "nvram", "kernel"). + +Different devices may be partitioned in a different ways. Some may use a fixed +flash layout set at production time. Some may use on-flash table that describes +the geometry and naming/purpose of each functional region. It is also possible +to see these methods mixed. + +To assist system software in locating partitions, we allow describing which +method is used for a given flash device. To describe the method there should be +a subnode of the flash device that is named 'partitions'. It must have a +'compatible' property, which is used to identify the method to use. + +When a single partition is represented with a DT node (it depends on a used +format) it may also be described using above rules ('compatible' and optionally +some extra properties / subnodes). It allows describing more complex, +hierarchical (multi-level) layouts and should be used if there is some +significant relation between partitions or some partition internally uses +another partitioning method. + +Available bindings are listed in the "partitions" subdirectory. + + +Fixed Partitions +================ + +Partitions can be represented by sub-nodes of a flash device. This can be used +on platforms which have strong conventions about which portions of a flash are +used for what purposes, but which don't use an on-flash partition table such +as RedBoot. + +The partition table should be a subnode of the flash node and should be named +'partitions'. This node should have the following property: +- compatible : (required) must be "fixed-partitions" +Partitions are then defined in subnodes of the partitions node. + +For backwards compatibility partitions as direct subnodes of the flash device are +supported. This use is discouraged. +NOTE: also for backwards compatibility, direct subnodes that have a compatible +string are not considered partitions, as they may be used for other bindings. + +#address-cells & #size-cells must both be present in the partitions subnode of the +flash device. There are two valid values for both: +<1>: for partitions that require a single 32-bit cell to represent their + size/address (aka the value is below 4 GiB) +<2>: for partitions that require two 32-bit cells to represent their + size/address (aka the value is 4 GiB or greater). + +Required properties: +- reg : The partition's offset and size within the flash + +Optional properties: +- label : The label / name for this partition. If omitted, the label is taken + from the node name (excluding the unit address). +- read-only : This parameter, if present, is a hint to Linux that this + partition should only be mounted read-only. This is usually used for flash + partitions containing early-boot firmware images or data which should not be + clobbered. +- lock : Do not unlock the partition at initialization time (not supported on + all devices) +- slc-mode: This parameter, if present, allows one to emulate SLC mode on a + partition attached to an MLC NAND thus making this partition immune to + paired-pages corruptions + +Examples: + + +flash@0 { + partitions { + compatible = "fixed-partitions"; + #address-cells = <1>; + #size-cells = <1>; + + partition@0 { + label = "u-boot"; + reg = <0x0000000 0x100000>; + read-only; + }; + + uimage@100000 { + reg = <0x0100000 0x200000>; + }; + }; +}; + +flash@1 { + partitions { + compatible = "fixed-partitions"; + #address-cells = <1>; + #size-cells = <2>; + + /* a 4 GiB partition */ + partition@0 { + label = "filesystem"; + reg = <0x00000000 0x1 0x00000000>; + }; + }; +}; + +flash@2 { + partitions { + compatible = "fixed-partitions"; + #address-cells = <2>; + #size-cells = <2>; + + /* an 8 GiB partition */ + partition@0 { + label = "filesystem #1"; + reg = <0x0 0x00000000 0x2 0x00000000>; + }; + + /* a 4 GiB partition */ + partition@200000000 { + label = "filesystem #2"; + reg = <0x2 0x00000000 0x1 0x00000000>; + }; + }; +}; + +flash@3 { + partitions { + compatible = "fixed-partitions"; + #address-cells = <1>; + #size-cells = <1>; + + partition@0 { + label = "bootloader"; + reg = <0x000000 0x100000>; + read-only; + }; + + firmware@100000 { + label = "firmware"; + reg = <0x100000 0xe00000>; + compatible = "brcm,trx"; + }; + + calibration@f00000 { + label = "calibration"; + reg = <0xf00000 0x100000>; + compatible = "fixed-partitions"; + ranges = <0 0xf00000 0x100000>; + #address-cells = <1>; + #size-cells = <1>; + + partition@0 { + label = "wifi0"; + reg = <0x000000 0x080000>; + }; + + partition@80000 { + label = "wifi1"; + reg = <0x080000 0x080000>; + }; + }; + }; +}; |