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1 | CFI or JEDEC memory-mapped NOR flash | ||
2 | |||
3 | Flash chips (Memory Technology Devices) are often used for solid state | ||
4 | file systems on embedded devices. | ||
5 | |||
6 | - compatible : should contain the specific model of flash chip(s) | ||
7 | used, if known, followed by either "cfi-flash" or "jedec-flash" | ||
8 | - reg : Address range(s) of the flash chip(s) | ||
9 | It's possible to (optionally) define multiple "reg" tuples so that | ||
10 | non-identical NOR chips can be described in one flash node. | ||
11 | - bank-width : Width (in bytes) of the flash bank. Equal to the | ||
12 | device width times the number of interleaved chips. | ||
13 | - device-width : (optional) Width of a single flash chip. If | ||
14 | omitted, assumed to be equal to 'bank-width'. | ||
15 | - #address-cells, #size-cells : Must be present if the flash has | ||
16 | sub-nodes representing partitions (see below). In this case | ||
17 | both #address-cells and #size-cells must be equal to 1. | ||
18 | |||
19 | For JEDEC compatible devices, the following additional properties | ||
20 | are defined: | ||
21 | |||
22 | - vendor-id : Contains the flash chip's vendor id (1 byte). | ||
23 | - device-id : Contains the flash chip's device id (1 byte). | ||
24 | |||
25 | In addition to the information on the flash bank itself, the | ||
26 | device tree may optionally contain additional information | ||
27 | describing partitions of the flash address space. This can be | ||
28 | used on platforms which have strong conventions about which | ||
29 | portions of the flash are used for what purposes, but which don't | ||
30 | use an on-flash partition table such as RedBoot. | ||
31 | |||
32 | Each partition is represented as a sub-node of the flash device. | ||
33 | Each node's name represents the name of the corresponding | ||
34 | partition of the flash device. | ||
35 | |||
36 | Flash partitions | ||
37 | - reg : The partition's offset and size within the flash bank. | ||
38 | - label : (optional) The label / name for this flash partition. | ||
39 | If omitted, the label is taken from the node name (excluding | ||
40 | the unit address). | ||
41 | - read-only : (optional) This parameter, if present, is a hint to | ||
42 | Linux that this flash partition should only be mounted | ||
43 | read-only. This is usually used for flash partitions | ||
44 | containing early-boot firmware images or data which should not | ||
45 | be clobbered. | ||
46 | |||
47 | Example: | ||
48 | |||
49 | flash@ff000000 { | ||
50 | compatible = "amd,am29lv128ml", "cfi-flash"; | ||
51 | reg = <ff000000 01000000>; | ||
52 | bank-width = <4>; | ||
53 | device-width = <1>; | ||
54 | #address-cells = <1>; | ||
55 | #size-cells = <1>; | ||
56 | fs@0 { | ||
57 | label = "fs"; | ||
58 | reg = <0 f80000>; | ||
59 | }; | ||
60 | firmware@f80000 { | ||
61 | label ="firmware"; | ||
62 | reg = <f80000 80000>; | ||
63 | read-only; | ||
64 | }; | ||
65 | }; | ||
66 | |||
67 | Here an example with multiple "reg" tuples: | ||
68 | |||
69 | flash@f0000000,0 { | ||
70 | #address-cells = <1>; | ||
71 | #size-cells = <1>; | ||
72 | compatible = "intel,PC48F4400P0VB", "cfi-flash"; | ||
73 | reg = <0 0x00000000 0x02000000 | ||
74 | 0 0x02000000 0x02000000>; | ||
75 | bank-width = <2>; | ||
76 | partition@0 { | ||
77 | label = "test-part1"; | ||
78 | reg = <0 0x04000000>; | ||
79 | }; | ||
80 | }; | ||