[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 <[email protected]>
Acked-by: Segher Boessenkool <[email protected]>
Signed-off-by: Paul Mackerras <[email protected]>

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
 

arch/powerpc/boot/dts/ebony.dts

@@ -138,13 +138,16 @@
 				interrupt-parent = <&UIC1>;
 
 				small-flash@0,80000 {
-					device_type = "rom";
-					compatible = "direct-mapped";
-					probe-type = "JEDEC";
+					compatible = "jedec-flash";
 					bank-width = <1>;
-					partitions = <0 80000>;
-					partition-names = "OpenBIOS";
 					reg = <0 80000 80000>;
+					#address-cells = <1>;
+					#size-cells = <1>;
+					partition@0 {
+						label = "OpenBIOS";
+						reg = <0 80000>;
+						read-only;
+					};
 				};
 
 				ds1743@1,0 {
@@ -154,14 +157,19 @@
 				};
 
 				large-flash@2,0 {
-					device_type = "rom";
-					compatible = "direct-mapped";
-					probe-type = "JEDEC";
+					compatible = "jedec-flash";
 					bank-width = <1>;
-					partitions = <0 380000
-						      380000 80000>;
-					partition-names = "fs", "firmware";
 					reg = <2 0 400000>;
+					#address-cells = <1>;
+					#size-cells = <1>;
+					partition@0 {
+						label = "fs";
+						reg = <0 380000>;
+					};
+					partition@380000 {
+						label = "firmware";
+						reg = <380000 80000>;
+					};
 				};
 
 				ir@3,0 {