[POWERPC] Document and implement an improved flash device binding for powerpc
This replaces the binding for flash chips in booting-without-of.txt
with an clarified and improved version. It also makes
drivers/mtd/maps/physmap_of.c recognize this new binding. Finally it
revises the Ebony device tree source to use the new binding as an
example.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Acked-by: Segher Boessenkool <segher@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/Documentation/powerpc/booting-without-of.txt b/Documentation/powerpc/booting-without-of.txt
index 76733a3..20e0e6c 100644
--- a/Documentation/powerpc/booting-without-of.txt
+++ b/Documentation/powerpc/booting-without-of.txt
@@ -50,7 +50,7 @@
g) Freescale SOC SEC Security Engines
h) Board Control and Status (BCSR)
i) Freescale QUICC Engine module (QE)
- j) Flash chip nodes
+ j) CFI or JEDEC memory-mapped NOR flash
k) Global Utilities Block
VII - Specifying interrupt information for devices
@@ -1757,45 +1757,69 @@
};
};
- j) Flash chip nodes
+ j) CFI or JEDEC memory-mapped NOR flash
Flash chips (Memory Technology Devices) are often used for solid state
file systems on embedded devices.
- Required properties:
+ - compatible : should contain the specific model of flash chip(s)
+ used, if known, followed by either "cfi-flash" or "jedec-flash"
+ - reg : Address range of the flash chip
+ - bank-width : Width (in bytes) of the flash bank. Equal to the
+ device width times the number of interleaved chips.
+ - device-width : (optional) Width of a single flash chip. If
+ omitted, assumed to be equal to 'bank-width'.
+ - #address-cells, #size-cells : Must be present if the flash has
+ sub-nodes representing partitions (see below). In this case
+ both #address-cells and #size-cells must be equal to 1.
- - device_type : has to be "rom"
- - compatible : Should specify what this flash device is compatible with.
- Currently, this is most likely to be "direct-mapped" (which
- corresponds to the MTD physmap mapping driver).
- - reg : Offset and length of the register set (or memory mapping) for
- the device.
- - bank-width : Width of the flash data bus in bytes. Required
- for the NOR flashes (compatible == "direct-mapped" and others) ONLY.
+ For JEDEC compatible devices, the following additional properties
+ are defined:
- Recommended properties :
+ - vendor-id : Contains the flash chip's vendor id (1 byte).
+ - device-id : Contains the flash chip's device id (1 byte).
- - partitions : Several pairs of 32-bit values where the first value is
- partition's offset from the start of the device and the second one is
- partition size in bytes with LSB used to signify a read only
- partition (so, the partition size should always be an even number).
- - partition-names : The list of concatenated zero terminated strings
- representing the partition names.
- - probe-type : The type of probe which should be done for the chip
- (JEDEC vs CFI actually). Valid ONLY for NOR flashes.
+ In addition to the information on the flash bank itself, the
+ device tree may optionally contain additional information
+ describing partitions of the flash address space. This can be
+ used on platforms which have strong conventions about which
+ portions of the flash are used for what purposes, but which don't
+ use an on-flash partition table such as RedBoot.
- Example:
+ Each partition is represented as a sub-node of the flash device.
+ Each node's name represents the name of the corresponding
+ partition of the flash device.
- flash@ff000000 {
- device_type = "rom";
- compatible = "direct-mapped";
- probe-type = "CFI";
- reg = <ff000000 01000000>;
- bank-width = <4>;
- partitions = <00000000 00f80000
- 00f80000 00080001>;
- partition-names = "fs\0firmware";
- };
+ Flash partitions
+ - reg : The partition's offset and size within the flash bank.
+ - label : (optional) The label / name for this flash 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 flash 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;
+ };
+ };
k) Global Utilities Block