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fc28c39f0e
Use physmap_of to access RAMs as mtd and add documenation for it. This approach is a lot less intrusive as adding an of-wrapper around plat-ram.c. As most extensions of plat-ram.c (e.g. custom map-functions) can't be mapped to the device tree anyhow, extending physmap_of seems to be the cleanest approach. Tested with a phyCORE-MPC5121e. Signed-off-by: Wolfram Sang <w.sang@pengutronix.de> Cc: Vitaly Wool <vwool@ru.mvista.com> Cc: Artem Bityutskiy <dedekind@infradead.org> Cc: Ken MacLeod <ken@bitsko.slc.ut.us> Cc: Albrecht Dreß <albrecht.dress@arcor.de> Acked-by: Grant Likely <grant.likely@secretlab.ca> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
90 lines
2.8 KiB
Text
90 lines
2.8 KiB
Text
CFI or JEDEC memory-mapped NOR flash, MTD-RAM (NVRAM...)
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Flash chips (Memory Technology Devices) are often used for solid state
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file systems on embedded devices.
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- compatible : should contain the specific model of mtd chip(s)
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used, if known, followed by either "cfi-flash", "jedec-flash"
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or "mtd-ram".
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- reg : Address range(s) of the mtd chip(s)
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It's possible to (optionally) define multiple "reg" tuples so that
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non-identical chips can be described in one node.
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- bank-width : Width (in bytes) of the bank. Equal to the
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device width times the number of interleaved chips.
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- device-width : (optional) Width of a single mtd chip. If
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omitted, assumed to be equal to 'bank-width'.
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- #address-cells, #size-cells : Must be present if the device has
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sub-nodes representing partitions (see below). In this case
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both #address-cells and #size-cells must be equal to 1.
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For JEDEC compatible devices, the following additional properties
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are defined:
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- vendor-id : Contains the flash chip's vendor id (1 byte).
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- device-id : Contains the flash chip's device id (1 byte).
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In addition to the information on the mtd bank itself, the
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device tree may optionally contain additional information
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describing partitions of the address space. This can be
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used on platforms which have strong conventions about which
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portions of a flash are used for what purposes, but which don't
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use an on-flash partition table such as RedBoot.
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Each partition is represented as a sub-node of the mtd device.
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Each node's name represents the name of the corresponding
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partition of the mtd device.
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Flash partitions
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- reg : The partition's offset and size within the mtd bank.
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- label : (optional) The label / name for this partition.
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If omitted, the label is taken from the node name (excluding
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the unit address).
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- read-only : (optional) This parameter, if present, is a hint to
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Linux that this partition should only be mounted
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read-only. This is usually used for flash partitions
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containing early-boot firmware images or data which should not
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be clobbered.
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Example:
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flash@ff000000 {
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compatible = "amd,am29lv128ml", "cfi-flash";
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reg = <ff000000 01000000>;
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bank-width = <4>;
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device-width = <1>;
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#address-cells = <1>;
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#size-cells = <1>;
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fs@0 {
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label = "fs";
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reg = <0 f80000>;
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};
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firmware@f80000 {
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label ="firmware";
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reg = <f80000 80000>;
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read-only;
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};
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};
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Here an example with multiple "reg" tuples:
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flash@f0000000,0 {
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#address-cells = <1>;
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#size-cells = <1>;
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compatible = "intel,PC48F4400P0VB", "cfi-flash";
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reg = <0 0x00000000 0x02000000
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0 0x02000000 0x02000000>;
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bank-width = <2>;
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partition@0 {
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label = "test-part1";
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reg = <0 0x04000000>;
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};
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};
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An example using SRAM:
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sram@2,0 {
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compatible = "samsung,k6f1616u6a", "mtd-ram";
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reg = <2 0 0x00200000>;
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bank-width = <2>;
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};
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