Kernel-3.10.0-957.el7_mtd-physmap

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.
  • 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).

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>;
};