Booting the Linux/ppc kernel without Open Firmware
--------------------------------------------------
-
(c) 2005 Benjamin Herrenschmidt <benh at kernel.crashing.org>,
IBM Corp.
(c) 2005 Becky Bruce <becky.bruce at freescale.com>,
(c) 2006 MontaVista Software, Inc.
Flash chip node definition
+Table of Contents
+=================
+
+ I - Introduction
+ 1) Entry point for arch/powerpc
+ 2) Board support
+
+ II - The DT block format
+ 1) Header
+ 2) Device tree generalities
+ 3) Device tree "structure" block
+ 4) Device tree "strings" block
+
+ III - Required content of the device tree
+ 1) Note about cells and address representation
+ 2) Note about "compatible" properties
+ 3) Note about "name" properties
+ 4) Note about node and property names and character set
+ 5) Required nodes and properties
+ a) The root node
+ b) The /cpus node
+ c) The /cpus/* nodes
+ d) the /memory node(s)
+ e) The /chosen node
+ f) the /soc<SOCname> node
+
+ IV - "dtc", the device tree compiler
+
+ V - Recommendations for a bootloader
+
+ VI - System-on-a-chip devices and nodes
+ 1) Defining child nodes of an SOC
+ 2) Representing devices without a current OF specification
+ a) MDIO IO device
+ b) Gianfar-compatible ethernet nodes
+ c) PHY nodes
+ d) Interrupt controllers
+ e) I2C
+ f) Freescale SOC USB controllers
+ g) Freescale SOC SEC Security Engines
+ h) Board Control and Status (BCSR)
+ i) Freescale QUICC Engine module (QE)
+ j) CFI or JEDEC memory-mapped NOR flash
+ k) Global Utilities Block
+
+ VII - Specifying interrupt information for devices
+ 1) interrupts property
+ 2) interrupt-parent property
+ 3) OpenPIC Interrupt Controllers
+ 4) ISA Interrupt Controllers
+
+ Appendix A - Sample SOC node for MPC8540
+
+
+Revision Information
+====================
+
May 18, 2005: Rev 0.1 - Initial draft, no chapter III yet.
May 19, 2005: Rev 0.2 - Add chapter III and bits & pieces here or
a list of properties, a list of child nodes, and an end token. Every
child node is a full node structure itself as defined above.
+NOTE: The above definition requires that all property definitions for
+a particular node MUST precede any subnode definitions for that node.
+Although the structure would not be ambiguous if properties and
+subnodes were intermingled, the kernel parser requires that the
+properties come first (up until at least 2.6.22). Any tools
+manipulating a flattened tree must take care to preserve this
+constraint.
+
4) Device tree "strings" block
In order to save space, property names, which are generally redundant,
network device. This is used by the bootwrapper to interpret
MAC addresses passed by the firmware when no information other
than indices is available to associate an address with a device.
+ - phy-connection-type : a string naming the controller/PHY interface type,
+ i.e., "mii" (default), "rmii", "gmii", "rgmii", "rgmii-id", "sgmii",
+ "tbi", or "rtbi". This property is only really needed if the connection
+ is of type "rgmii-id", as all other connection types are detected by
+ hardware.
+
Example:
Basically, it is a bus of devices, that could act more or less
as a complete entity (UCC, USB etc ). All of them should be siblings on
the "root" qe node, using the common properties from there.
- The description below applies to the the qe of MPC8360 and
+ The description below applies to the qe of MPC8360 and
more nodes and properties would be extended in the future.
i) Root QE device
- assignment : function number of the pin according to the Pin Assignment
tables in User Manual. Each pin can have up to 4 possible functions in
QE and two options for CPM.
- - has_irq : indicates if the pin is used as source of exteral
+ - has_irq : indicates if the pin is used as source of external
interrupts.
Example:
};
};
- g) 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.
+
+ 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
- - 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.
+ The global utilities block controls power management, I/O device
+ enabling, power-on-reset configuration monitoring, general-purpose
+ I/O signal configuration, alternate function selection for multiplexed
+ signals, and clock control.
- Recommended properties :
+ Required 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.
+ - compatible : Should define the compatible device type for
+ global-utilities.
+ - reg : Offset and length of the register set for the device.
- Example:
+ Recommended properties:
+
+ - fsl,has-rstcr : Indicates that the global utilities register set
+ contains a functioning "reset control register" (i.e. the board
+ is wired to reset upon setting the HRESET_REQ bit in this register).
- 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";
- };
+ Example:
+
+ global-utilities@e0000 { /* global utilities block */
+ compatible = "fsl,mpc8548-guts";
+ reg = <e0000 1000>;
+ fsl,has-rstcr;
+ };
More devices will be defined as this spec matures.
projects / linux-2.6-omap-h63xx.git / blobdiff