[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>

1 files changed, 58 insertions, 34 deletions

diff --git a/Documentation/powerpc/booting-without-of.txt b/Documentation/powerpc/booting-without-of.txt
index 76733a3962f0..20e0e6cb0347 100644
--- a/Documentation/powerpc/booting-without-of.txt
+++ b/Documentation/powerpc/booting-without-of.txt
@@ -50,7 +50,7 @@ Table of Contents
       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 @@ platforms are moved over to use the flattened-device-tree model.
                 };
         };
 
-    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.
+
+    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 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.
+
+    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 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.
 
-     - 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.
-
-    Recommended properties :
-
-     - 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.
-
-   Example:
+    Example:
 
-        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@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