xref: /kernel/linux/linux-5.10/Documentation/devicetree/bindings/mtd/mtd-physmap.txt

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.
 - addr-gpios : (optional) List of GPIO descriptors that will be used to
   address the MSBs address lines. The order goes from LSB to MSB.

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>;
	};

An example using gpio-addrs

	flash@20000000 {
		#address-cells = <1>;
		#size-cells = <1>;
		compatible = "cfi-flash", "jedec-flash";
		reg = <0x20000000 0x02000000>;
		ranges = <0 0x00000000 0x02000000
		          1 0x02000000 0x02000000>;
		bank-width = <2>;
		addr-gpios = <&gpio1 2 GPIO_ACTIVE_HIGH>;
		partition@0 {
			label = "test-part1";
			reg = <0 0x04000000>;
		};
	};