| Stefan Roese | efcc2da | 2009-04-16 15:11:54 -0600 | [diff] [blame^] | 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 of the flash chip |
| 9 | - bank-width : Width (in bytes) of the flash bank. Equal to the |
| 10 | device width times the number of interleaved chips. |
| 11 | - device-width : (optional) Width of a single flash chip. If |
| 12 | omitted, assumed to be equal to 'bank-width'. |
| 13 | - #address-cells, #size-cells : Must be present if the flash has |
| 14 | sub-nodes representing partitions (see below). In this case |
| 15 | both #address-cells and #size-cells must be equal to 1. |
| 16 | |
| 17 | For JEDEC compatible devices, the following additional properties |
| 18 | are defined: |
| 19 | |
| 20 | - vendor-id : Contains the flash chip's vendor id (1 byte). |
| 21 | - device-id : Contains the flash chip's device id (1 byte). |
| 22 | |
| 23 | In addition to the information on the flash bank itself, the |
| 24 | device tree may optionally contain additional information |
| 25 | describing partitions of the flash address space. This can be |
| 26 | used on platforms which have strong conventions about which |
| 27 | portions of the flash are used for what purposes, but which don't |
| 28 | use an on-flash partition table such as RedBoot. |
| 29 | |
| 30 | Each partition is represented as a sub-node of the flash device. |
| 31 | Each node's name represents the name of the corresponding |
| 32 | partition of the flash device. |
| 33 | |
| 34 | Flash partitions |
| 35 | - reg : The partition's offset and size within the flash bank. |
| 36 | - label : (optional) The label / name for this flash partition. |
| 37 | If omitted, the label is taken from the node name (excluding |
| 38 | the unit address). |
| 39 | - read-only : (optional) This parameter, if present, is a hint to |
| 40 | Linux that this flash partition should only be mounted |
| 41 | read-only. This is usually used for flash partitions |
| 42 | containing early-boot firmware images or data which should not |
| 43 | be clobbered. |
| 44 | |
| 45 | Example: |
| 46 | |
| 47 | flash@ff000000 { |
| 48 | compatible = "amd,am29lv128ml", "cfi-flash"; |
| 49 | reg = <ff000000 01000000>; |
| 50 | bank-width = <4>; |
| 51 | device-width = <1>; |
| 52 | #address-cells = <1>; |
| 53 | #size-cells = <1>; |
| 54 | fs@0 { |
| 55 | label = "fs"; |
| 56 | reg = <0 f80000>; |
| 57 | }; |
| 58 | firmware@f80000 { |
| 59 | label ="firmware"; |
| 60 | reg = <f80000 80000>; |
| 61 | read-only; |
| 62 | }; |
| 63 | }; |