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CFI or JEDEC memory-mapped NOR flash, MTD-RAM (NVRAM...)
Flash chips (Memory Technology Devices) are often used for solid state
file systems on embedded devices.
- compatible : should contain the specific model of mtd chip(s)
used, if known, followed by either "cfi-flash", "jedec-flash",
"mtd-ram" or "mtd-rom".
- reg : Address range(s) of the mtd chip(s)
It's possible to (optionally) define multiple "reg" tuples so that
non-identical chips can be described in one node.
- bank-width : Width (in bytes) of the bank. Equal to the
device width times the number of interleaved chips.
- device-width : (optional) Width of a single mtd chip. If
omitted, assumed to be equal to 'bank-width'.
- #address-cells, #size-cells : Must be present if the device has
sub-nodes representing partitions (see below). In this case
both #address-cells and #size-cells must be equal to 1.
- no-unaligned-direct-access: boolean to disable the default direct
mapping of the flash.
On some platforms (e.g. MPC5200) a direct 1:1 mapping may cause
problems with JFFS2 usage, as the local bus (LPB) doesn't support
unaligned accesses as implemented in the JFFS2 code via memcpy().
By defining "no-unaligned-direct-access", the flash will not be
exposed directly to the MTD users (e.g. JFFS2) any more.
- linux,mtd-name: allow to specify the mtd name for retro capability with
physmap-flash drivers as boot loader pass the mtd partition via the old
device name physmap-flash.
- use-advanced-sector-protection: boolean to enable support for the
advanced sector protection (Spansion: PPB - Persistent Protection
Bits) locking.
For JEDEC compatible devices, the following additional properties
are defined:
- vendor-id : Contains the flash chip's vendor id (1 byte).
- device-id : Contains the flash chip's device id (1 byte).
For ROM compatible devices (and ROM fallback from cfi-flash), the following
additional (optional) property is defined:
- erase-size : The chip's physical erase block size in bytes.
The device tree may optionally contain endianness property.
little-endian or big-endian : It Represents the endianness that should be used
by the controller to properly read/write data
from/to the flash. If this property is missing,
the endianness is chosen by the system
(potentially based on extra configuration options).
The device tree may optionally contain sub-nodes describing partitions of the
address space. See partition.txt for more detail.
Example:
flash@ff000000 {
compatible = "amd,am29lv128ml", "cfi-flash";
reg = <ff000000 01000000>;
bank-width = <4>;
device-width = <1>;
#address-cells = <1>;
#size-cells = <1>;
fs@0 {
label = "fs";
reg = <0 f80000>;
};
firmware@f80000 {
label ="firmware";
reg = <f80000 80000>;
read-only;
};
};
Here an example with multiple "reg" tuples:
flash@f0000000,0 {
#address-cells = <1>;
#size-cells = <1>;
compatible = "intel,PC48F4400P0VB", "cfi-flash";
reg = <0 0x00000000 0x02000000
0 0x02000000 0x02000000>;
bank-width = <2>;
partition@0 {
label = "test-part1";
reg = <0 0x04000000>;
};
};
An example using SRAM:
sram@2,0 {
compatible = "samsung,k6f1616u6a", "mtd-ram";
reg = <2 0 0x00200000>;
bank-width = <2>;
};
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