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>
91 lines
2.8 KiB
Plaintext
91 lines
2.8 KiB
Plaintext
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"
|
|
or "mtd-ram".
|
|
- 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.
|
|
|
|
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).
|
|
|
|
In addition to the information on the mtd bank itself, the
|
|
device tree may optionally contain additional information
|
|
describing partitions of the address space. 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.
|
|
|
|
Each partition is represented as a sub-node of the mtd device.
|
|
Each node's name represents the name of the corresponding
|
|
partition of the mtd device.
|
|
|
|
Flash partitions
|
|
- reg : The partition's offset and size within the mtd bank.
|
|
- label : (optional) The label / name for this partition.
|
|
If omitted, the label is taken from the node name (excluding
|
|
the unit address).
|
|
- read-only : (optional) 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.
|
|
|
|
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>;
|
|
};
|
|
|