Documentation / powerpc / booting-without-of.txt

Based on kernel version 2.6.37. Page generated on 2011-03-22 21:57 EST.

	           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>,
	    Freescale Semiconductor, FSL SOC and 32-bit additions
	(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) PHY nodes
	      b) Interrupt controllers
	      c) 4xx/Axon EMAC ethernet nodes
	      d) Xilinx IP cores
	      e) USB EHCI controllers
	      f) MDIO on GPIOs
	      g) SPI busses
	
	  VII - Specifying interrupt information for devices
	    1) interrupts property
	    2) interrupt-parent property
	    3) OpenPIC Interrupt Controllers
	    4) ISA Interrupt Controllers
	
	  VIII - Specifying device power management information (sleep property)
	
	  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
	                           clarifies the fact that a lot of things are
	                           optional, the kernel only requires a very
	                           small device tree, though it is encouraged
	                           to provide an as complete one as possible.
	
	   May 24, 2005: Rev 0.3 - Precise that DT block has to be in RAM
				 - Misc fixes
				 - Define version 3 and new format version 16
				   for the DT block (version 16 needs kernel
				   patches, will be fwd separately).
				   String block now has a size, and full path
				   is replaced by unit name for more
				   compactness.
				   linux,phandle is made optional, only nodes
				   that are referenced by other nodes need it.
				   "name" property is now automatically
				   deduced from the unit name
	
	   June 1, 2005: Rev 0.4 - Correct confusion between OF_DT_END and
	                           OF_DT_END_NODE in structure definition.
	                         - Change version 16 format to always align
	                           property data to 4 bytes. Since tokens are
	                           already aligned, that means no specific
	                           required alignment between property size
	                           and property data. The old style variable
	                           alignment would make it impossible to do
	                           "simple" insertion of properties using
	                           memmove (thanks Milton for
	                           noticing). Updated kernel patch as well
				 - Correct a few more alignment constraints
				 - Add a chapter about the device-tree
	                           compiler and the textural representation of
	                           the tree that can be "compiled" by dtc.
	
	   November 21, 2005: Rev 0.5
				 - Additions/generalizations for 32-bit
				 - Changed to reflect the new arch/powerpc
				   structure
				 - Added chapter VI
	
	
	 ToDo:
		- Add some definitions of interrupt tree (simple/complex)
		- Add some definitions for PCI host bridges
		- Add some common address format examples
		- Add definitions for standard properties and "compatible"
		  names for cells that are not already defined by the existing
		  OF spec.
		- Compare FSL SOC use of PCI to standard and make sure no new
		  node definition required.
		- Add more information about node definitions for SOC devices
	  	  that currently have no standard, like the FSL CPM.
	
	
	I - Introduction
	================
	
	During the recent development of the Linux/ppc64 kernel, and more
	specifically, the addition of new platform types outside of the old
	IBM pSeries/iSeries pair, it was decided to enforce some strict rules
	regarding the kernel entry and bootloader <-> kernel interfaces, in
	order to avoid the degeneration that had become the ppc32 kernel entry
	point and the way a new platform should be added to the kernel. The
	legacy iSeries platform breaks those rules as it predates this scheme,
	but no new board support will be accepted in the main tree that
	doesn't follows them properly.  In addition, since the advent of the
	arch/powerpc merged architecture for ppc32 and ppc64, new 32-bit
	platforms and 32-bit platforms which move into arch/powerpc will be
	required to use these rules as well.
	
	The main requirement that will be defined in more detail below is
	the presence of a device-tree whose format is defined after Open
	Firmware specification. However, in order to make life easier
	to embedded board vendors, the kernel doesn't require the device-tree
	to represent every device in the system and only requires some nodes
	and properties to be present. This will be described in detail in
	section III, but, for example, the kernel does not require you to
	create a node for every PCI device in the system. It is a requirement
	to have a node for PCI host bridges in order to provide interrupt
	routing informations and memory/IO ranges, among others. It is also
	recommended to define nodes for on chip devices and other busses that
	don't specifically fit in an existing OF specification. This creates a
	great flexibility in the way the kernel can then probe those and match
	drivers to device, without having to hard code all sorts of tables. It
	also makes it more flexible for board vendors to do minor hardware
	upgrades without significantly impacting the kernel code or cluttering
	it with special cases.
	
	
	1) Entry point for arch/powerpc
	-------------------------------
	
	   There is one and one single entry point to the kernel, at the start
	   of the kernel image. That entry point supports two calling
	   conventions:
	
	        a) Boot from Open Firmware. If your firmware is compatible
	        with Open Firmware (IEEE 1275) or provides an OF compatible
	        client interface API (support for "interpret" callback of
	        forth words isn't required), you can enter the kernel with:
	
	              r5 : OF callback pointer as defined by IEEE 1275
	              bindings to powerpc. Only the 32-bit client interface
	              is currently supported
	
	              r3, r4 : address & length of an initrd if any or 0
	
	              The MMU is either on or off; the kernel will run the
	              trampoline located in arch/powerpc/kernel/prom_init.c to
	              extract the device-tree and other information from open
	              firmware and build a flattened device-tree as described
	              in b). prom_init() will then re-enter the kernel using
	              the second method. This trampoline code runs in the
	              context of the firmware, which is supposed to handle all
	              exceptions during that time.
	
	        b) Direct entry with a flattened device-tree block. This entry
	        point is called by a) after the OF trampoline and can also be
	        called directly by a bootloader that does not support the Open
	        Firmware client interface. It is also used by "kexec" to
	        implement "hot" booting of a new kernel from a previous
	        running one. This method is what I will describe in more
	        details in this document, as method a) is simply standard Open
	        Firmware, and thus should be implemented according to the
	        various standard documents defining it and its binding to the
	        PowerPC platform. The entry point definition then becomes:
	
	                r3 : physical pointer to the device-tree block
	                (defined in chapter II) in RAM
	
	                r4 : physical pointer to the kernel itself. This is
	                used by the assembly code to properly disable the MMU
	                in case you are entering the kernel with MMU enabled
	                and a non-1:1 mapping.
	
	                r5 : NULL (as to differentiate with method a)
	
	        Note about SMP entry: Either your firmware puts your other
	        CPUs in some sleep loop or spin loop in ROM where you can get
	        them out via a soft reset or some other means, in which case
	        you don't need to care, or you'll have to enter the kernel
	        with all CPUs. The way to do that with method b) will be
	        described in a later revision of this document.
	
	
	2) Board support
	----------------
	
	64-bit kernels:
	
	   Board supports (platforms) are not exclusive config options. An
	   arbitrary set of board supports can be built in a single kernel
	   image. The kernel will "know" what set of functions to use for a
	   given platform based on the content of the device-tree. Thus, you
	   should:
	
	        a) add your platform support as a _boolean_ option in
	        arch/powerpc/Kconfig, following the example of PPC_PSERIES,
	        PPC_PMAC and PPC_MAPLE. The later is probably a good
	        example of a board support to start from.
	
	        b) create your main platform file as
	        "arch/powerpc/platforms/myplatform/myboard_setup.c" and add it
	        to the Makefile under the condition of your CONFIG_
	        option. This file will define a structure of type "ppc_md"
	        containing the various callbacks that the generic code will
	        use to get to your platform specific code
	
	        c) Add a reference to your "ppc_md" structure in the
	        "machines" table in arch/powerpc/kernel/setup_64.c if you are
	        a 64-bit platform.
	
	        d) request and get assigned a platform number (see PLATFORM_*
	        constants in arch/powerpc/include/asm/processor.h
	
	32-bit embedded kernels:
	
	  Currently, board support is essentially an exclusive config option.
	  The kernel is configured for a single platform.  Part of the reason
	  for this is to keep kernels on embedded systems small and efficient;
	  part of this is due to the fact the code is already that way. In the
	  future, a kernel may support multiple platforms, but only if the
	  platforms feature the same core architecture.  A single kernel build
	  cannot support both configurations with Book E and configurations
	  with classic Powerpc architectures.
	
	  32-bit embedded platforms that are moved into arch/powerpc using a
	  flattened device tree should adopt the merged tree practice of
	  setting ppc_md up dynamically, even though the kernel is currently
	  built with support for only a single platform at a time.  This allows
	  unification of the setup code, and will make it easier to go to a
	  multiple-platform-support model in the future.
	
	NOTE: I believe the above will be true once Ben's done with the merge
	of the boot sequences.... someone speak up if this is wrong!
	
	  To add a 32-bit embedded platform support, follow the instructions
	  for 64-bit platforms above, with the exception that the Kconfig
	  option should be set up such that the kernel builds exclusively for
	  the platform selected.  The processor type for the platform should
	  enable another config option to select the specific board
	  supported.
	
	NOTE: If Ben doesn't merge the setup files, may need to change this to
	point to setup_32.c
	
	
	   I will describe later the boot process and various callbacks that
	   your platform should implement.
	
	
	II - The DT block format
	========================
	
	
	This chapter defines the actual format of the flattened device-tree
	passed to the kernel. The actual content of it and kernel requirements
	are described later. You can find example of code manipulating that
	format in various places, including arch/powerpc/kernel/prom_init.c
	which will generate a flattened device-tree from the Open Firmware
	representation, or the fs2dt utility which is part of the kexec tools
	which will generate one from a filesystem representation. It is
	expected that a bootloader like uboot provides a bit more support,
	that will be discussed later as well.
	
	Note: The block has to be in main memory. It has to be accessible in
	both real mode and virtual mode with no mapping other than main
	memory. If you are writing a simple flash bootloader, it should copy
	the block to RAM before passing it to the kernel.
	
	
	1) Header
	---------
	
	   The kernel is entered with r3 pointing to an area of memory that is
	   roughly described in arch/powerpc/include/asm/prom.h by the structure
	   boot_param_header:
	
	struct boot_param_header {
	        u32     magic;                  /* magic word OF_DT_HEADER */
	        u32     totalsize;              /* total size of DT block */
	        u32     off_dt_struct;          /* offset to structure */
	        u32     off_dt_strings;         /* offset to strings */
	        u32     off_mem_rsvmap;         /* offset to memory reserve map
	                                           */
	        u32     version;                /* format version */
	        u32     last_comp_version;      /* last compatible version */
	
	        /* version 2 fields below */
	        u32     boot_cpuid_phys;        /* Which physical CPU id we're
	                                           booting on */
	        /* version 3 fields below */
	        u32     size_dt_strings;        /* size of the strings block */
	
	        /* version 17 fields below */
	        u32	size_dt_struct;		/* size of the DT structure block */
	};
	
	   Along with the constants:
	
	/* Definitions used by the flattened device tree */
	#define OF_DT_HEADER            0xd00dfeed      /* 4: version,
							   4: total size */
	#define OF_DT_BEGIN_NODE        0x1             /* Start node: full name
							   */
	#define OF_DT_END_NODE          0x2             /* End node */
	#define OF_DT_PROP              0x3             /* Property: name off,
	                                                   size, content */
	#define OF_DT_END               0x9
	
	   All values in this header are in big endian format, the various
	   fields in this header are defined more precisely below. All
	   "offset" values are in bytes from the start of the header; that is
	   from the value of r3.
	
	   - magic
	
	     This is a magic value that "marks" the beginning of the
	     device-tree block header. It contains the value 0xd00dfeed and is
	     defined by the constant OF_DT_HEADER
	
	   - totalsize
	
	     This is the total size of the DT block including the header. The
	     "DT" block should enclose all data structures defined in this
	     chapter (who are pointed to by offsets in this header). That is,
	     the device-tree structure, strings, and the memory reserve map.
	
	   - off_dt_struct
	
	     This is an offset from the beginning of the header to the start
	     of the "structure" part the device tree. (see 2) device tree)
	
	   - off_dt_strings
	
	     This is an offset from the beginning of the header to the start
	     of the "strings" part of the device-tree
	
	   - off_mem_rsvmap
	
	     This is an offset from the beginning of the header to the start
	     of the reserved memory map. This map is a list of pairs of 64-
	     bit integers. Each pair is a physical address and a size. The
	     list is terminated by an entry of size 0. This map provides the
	     kernel with a list of physical memory areas that are "reserved"
	     and thus not to be used for memory allocations, especially during
	     early initialization. The kernel needs to allocate memory during
	     boot for things like un-flattening the device-tree, allocating an
	     MMU hash table, etc... Those allocations must be done in such a
	     way to avoid overriding critical things like, on Open Firmware
	     capable machines, the RTAS instance, or on some pSeries, the TCE
	     tables used for the iommu. Typically, the reserve map should
	     contain _at least_ this DT block itself (header,total_size). If
	     you are passing an initrd to the kernel, you should reserve it as
	     well. You do not need to reserve the kernel image itself. The map
	     should be 64-bit aligned.
	
	   - version
	
	     This is the version of this structure. Version 1 stops
	     here. Version 2 adds an additional field boot_cpuid_phys.
	     Version 3 adds the size of the strings block, allowing the kernel
	     to reallocate it easily at boot and free up the unused flattened
	     structure after expansion. Version 16 introduces a new more
	     "compact" format for the tree itself that is however not backward
	     compatible. Version 17 adds an additional field, size_dt_struct,
	     allowing it to be reallocated or moved more easily (this is
	     particularly useful for bootloaders which need to make
	     adjustments to a device tree based on probed information). You
	     should always generate a structure of the highest version defined
	     at the time of your implementation. Currently that is version 17,
	     unless you explicitly aim at being backward compatible.
	
	   - last_comp_version
	
	     Last compatible version. This indicates down to what version of
	     the DT block you are backward compatible. For example, version 2
	     is backward compatible with version 1 (that is, a kernel build
	     for version 1 will be able to boot with a version 2 format). You
	     should put a 1 in this field if you generate a device tree of
	     version 1 to 3, or 16 if you generate a tree of version 16 or 17
	     using the new unit name format.
	
	   - boot_cpuid_phys
	
	     This field only exist on version 2 headers. It indicate which
	     physical CPU ID is calling the kernel entry point. This is used,
	     among others, by kexec. If you are on an SMP system, this value
	     should match the content of the "reg" property of the CPU node in
	     the device-tree corresponding to the CPU calling the kernel entry
	     point (see further chapters for more informations on the required
	     device-tree contents)
	
	   - size_dt_strings
	
	     This field only exists on version 3 and later headers.  It
	     gives the size of the "strings" section of the device tree (which
	     starts at the offset given by off_dt_strings).
	
	   - size_dt_struct
	
	     This field only exists on version 17 and later headers.  It gives
	     the size of the "structure" section of the device tree (which
	     starts at the offset given by off_dt_struct).
	
	   So the typical layout of a DT block (though the various parts don't
	   need to be in that order) looks like this (addresses go from top to
	   bottom):
	
	
	             ------------------------------
	       r3 -> |  struct boot_param_header  |
	             ------------------------------
	             |      (alignment gap) (*)   |
	             ------------------------------
	             |      memory reserve map    |
	             ------------------------------
	             |      (alignment gap)       |
	             ------------------------------
	             |                            |
	             |    device-tree structure   |
	             |                            |
	             ------------------------------
	             |      (alignment gap)       |
	             ------------------------------
	             |                            |
	             |     device-tree strings    |
	             |                            |
	      -----> ------------------------------
	      |
	      |
	      --- (r3 + totalsize)
	
	  (*) The alignment gaps are not necessarily present; their presence
	      and size are dependent on the various alignment requirements of
	      the individual data blocks.
	
	
	2) Device tree generalities
	---------------------------
	
	This device-tree itself is separated in two different blocks, a
	structure block and a strings block. Both need to be aligned to a 4
	byte boundary.
	
	First, let's quickly describe the device-tree concept before detailing
	the storage format. This chapter does _not_ describe the detail of the
	required types of nodes & properties for the kernel, this is done
	later in chapter III.
	
	The device-tree layout is strongly inherited from the definition of
	the Open Firmware IEEE 1275 device-tree. It's basically a tree of
	nodes, each node having two or more named properties. A property can
	have a value or not.
	
	It is a tree, so each node has one and only one parent except for the
	root node who has no parent.
	
	A node has 2 names. The actual node name is generally contained in a
	property of type "name" in the node property list whose value is a
	zero terminated string and is mandatory for version 1 to 3 of the
	format definition (as it is in Open Firmware). Version 16 makes it
	optional as it can generate it from the unit name defined below.
	
	There is also a "unit name" that is used to differentiate nodes with
	the same name at the same level, it is usually made of the node
	names, the "@" sign, and a "unit address", which definition is
	specific to the bus type the node sits on.
	
	The unit name doesn't exist as a property per-se but is included in
	the device-tree structure. It is typically used to represent "path" in
	the device-tree. More details about the actual format of these will be
	below.
	
	The kernel powerpc generic code does not make any formal use of the
	unit address (though some board support code may do) so the only real
	requirement here for the unit address is to ensure uniqueness of
	the node unit name at a given level of the tree. Nodes with no notion
	of address and no possible sibling of the same name (like /memory or
	/cpus) may omit the unit address in the context of this specification,
	or use the "@0" default unit address. The unit name is used to define
	a node "full path", which is the concatenation of all parent node
	unit names separated with "/".
	
	The root node doesn't have a defined name, and isn't required to have
	a name property either if you are using version 3 or earlier of the
	format. It also has no unit address (no @ symbol followed by a unit
	address). The root node unit name is thus an empty string. The full
	path to the root node is "/".
	
	Every node which actually represents an actual device (that is, a node
	which isn't only a virtual "container" for more nodes, like "/cpus"
	is) is also required to have a "device_type" property indicating the
	type of node .
	
	Finally, every node that can be referenced from a property in another
	node is required to have a "linux,phandle" property. Real open
	firmware implementations provide a unique "phandle" value for every
	node that the "prom_init()" trampoline code turns into
	"linux,phandle" properties. However, this is made optional if the
	flattened device tree is used directly. An example of a node
	referencing another node via "phandle" is when laying out the
	interrupt tree which will be described in a further version of this
	document.
	
	This "linux, phandle" property is a 32-bit value that uniquely
	identifies a node. You are free to use whatever values or system of
	values, internal pointers, or whatever to generate these, the only
	requirement is that every node for which you provide that property has
	a unique value for it.
	
	Here is an example of a simple device-tree. In this example, an "o"
	designates a node followed by the node unit name. Properties are
	presented with their name followed by their content. "content"
	represents an ASCII string (zero terminated) value, while <content>
	represents a 32-bit hexadecimal value. The various nodes in this
	example will be discussed in a later chapter. At this point, it is
	only meant to give you a idea of what a device-tree looks like. I have
	purposefully kept the "name" and "linux,phandle" properties which
	aren't necessary in order to give you a better idea of what the tree
	looks like in practice.
	
	  / o device-tree
	      |- name = "device-tree"
	      |- model = "MyBoardName"
	      |- compatible = "MyBoardFamilyName"
	      |- #address-cells = <2>
	      |- #size-cells = <2>
	      |- linux,phandle = <0>
	      |
	      o cpus
	      | | - name = "cpus"
	      | | - linux,phandle = <1>
	      | | - #address-cells = <1>
	      | | - #size-cells = <0>
	      | |
	      | o PowerPC,970@0
	      |   |- name = "PowerPC,970"
	      |   |- device_type = "cpu"
	      |   |- reg = <0>
	      |   |- clock-frequency = <5f5e1000>
	      |   |- 64-bit
	      |   |- linux,phandle = <2>
	      |
	      o memory@0
	      | |- name = "memory"
	      | |- device_type = "memory"
	      | |- reg = <00000000 00000000 00000000 20000000>
	      | |- linux,phandle = <3>
	      |
	      o chosen
	        |- name = "chosen"
	        |- bootargs = "root=/dev/sda2"
	        |- linux,phandle = <4>
	
	This tree is almost a minimal tree. It pretty much contains the
	minimal set of required nodes and properties to boot a linux kernel;
	that is, some basic model informations at the root, the CPUs, and the
	physical memory layout.  It also includes misc information passed
	through /chosen, like in this example, the platform type (mandatory)
	and the kernel command line arguments (optional).
	
	The /cpus/PowerPC,970@0/64-bit property is an example of a
	property without a value. All other properties have a value. The
	significance of the #address-cells and #size-cells properties will be
	explained in chapter IV which defines precisely the required nodes and
	properties and their content.
	
	
	3) Device tree "structure" block
	
	The structure of the device tree is a linearized tree structure. The
	"OF_DT_BEGIN_NODE" token starts a new node, and the "OF_DT_END_NODE"
	ends that node definition. Child nodes are simply defined before
	"OF_DT_END_NODE" (that is nodes within the node). A 'token' is a 32
	bit value. The tree has to be "finished" with a OF_DT_END token
	
	Here's the basic structure of a single node:
	
	     * token OF_DT_BEGIN_NODE (that is 0x00000001)
	     * for version 1 to 3, this is the node full path as a zero
	       terminated string, starting with "/". For version 16 and later,
	       this is the node unit name only (or an empty string for the
	       root node)
	     * [align gap to next 4 bytes boundary]
	     * for each property:
	        * token OF_DT_PROP (that is 0x00000003)
	        * 32-bit value of property value size in bytes (or 0 if no
	          value)
	        * 32-bit value of offset in string block of property name
	        * property value data if any
	        * [align gap to next 4 bytes boundary]
	     * [child nodes if any]
	     * token OF_DT_END_NODE (that is 0x00000002)
	
	So the node content can be summarized as a start token, a full path,
	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,
	are stored separately in the "strings" block. This block is simply the
	whole bunch of zero terminated strings for all property names
	concatenated together. The device-tree property definitions in the
	structure block will contain offset values from the beginning of the
	strings block.
	
	
	III - Required content of the device tree
	=========================================
	
	WARNING: All "linux,*" properties defined in this document apply only
	to a flattened device-tree. If your platform uses a real
	implementation of Open Firmware or an implementation compatible with
	the Open Firmware client interface, those properties will be created
	by the trampoline code in the kernel's prom_init() file. For example,
	that's where you'll have to add code to detect your board model and
	set the platform number. However, when using the flattened device-tree
	entry point, there is no prom_init() pass, and thus you have to
	provide those properties yourself.
	
	
	1) Note about cells and address representation
	----------------------------------------------
	
	The general rule is documented in the various Open Firmware
	documentations. If you choose to describe a bus with the device-tree
	and there exist an OF bus binding, then you should follow the
	specification. However, the kernel does not require every single
	device or bus to be described by the device tree.
	
	In general, the format of an address for a device is defined by the
	parent bus type, based on the #address-cells and #size-cells
	properties.  Note that the parent's parent definitions of #address-cells
	and #size-cells are not inherited so every node with children must specify
	them.  The kernel requires the root node to have those properties defining
	addresses format for devices directly mapped on the processor bus.
	
	Those 2 properties define 'cells' for representing an address and a
	size. A "cell" is a 32-bit number. For example, if both contain 2
	like the example tree given above, then an address and a size are both
	composed of 2 cells, and each is a 64-bit number (cells are
	concatenated and expected to be in big endian format). Another example
	is the way Apple firmware defines them, with 2 cells for an address
	and one cell for a size.  Most 32-bit implementations should define
	#address-cells and #size-cells to 1, which represents a 32-bit value.
	Some 32-bit processors allow for physical addresses greater than 32
	bits; these processors should define #address-cells as 2.
	
	"reg" properties are always a tuple of the type "address size" where
	the number of cells of address and size is specified by the bus
	#address-cells and #size-cells. When a bus supports various address
	spaces and other flags relative to a given address allocation (like
	prefetchable, etc...) those flags are usually added to the top level
	bits of the physical address. For example, a PCI physical address is
	made of 3 cells, the bottom two containing the actual address itself
	while the top cell contains address space indication, flags, and pci
	bus & device numbers.
	
	For busses that support dynamic allocation, it's the accepted practice
	to then not provide the address in "reg" (keep it 0) though while
	providing a flag indicating the address is dynamically allocated, and
	then, to provide a separate "assigned-addresses" property that
	contains the fully allocated addresses. See the PCI OF bindings for
	details.
	
	In general, a simple bus with no address space bits and no dynamic
	allocation is preferred if it reflects your hardware, as the existing
	kernel address parsing functions will work out of the box. If you
	define a bus type with a more complex address format, including things
	like address space bits, you'll have to add a bus translator to the
	prom_parse.c file of the recent kernels for your bus type.
	
	The "reg" property only defines addresses and sizes (if #size-cells is
	non-0) within a given bus. In order to translate addresses upward
	(that is into parent bus addresses, and possibly into CPU physical
	addresses), all busses must contain a "ranges" property. If the
	"ranges" property is missing at a given level, it's assumed that
	translation isn't possible, i.e., the registers are not visible on the
	parent bus.  The format of the "ranges" property for a bus is a list
	of:
	
		bus address, parent bus address, size
	
	"bus address" is in the format of the bus this bus node is defining,
	that is, for a PCI bridge, it would be a PCI address. Thus, (bus
	address, size) defines a range of addresses for child devices. "parent
	bus address" is in the format of the parent bus of this bus. For
	example, for a PCI host controller, that would be a CPU address. For a
	PCI<->ISA bridge, that would be a PCI address. It defines the base
	address in the parent bus where the beginning of that range is mapped.
	
	For a new 64-bit powerpc board, I recommend either the 2/2 format or
	Apple's 2/1 format which is slightly more compact since sizes usually
	fit in a single 32-bit word.   New 32-bit powerpc boards should use a
	1/1 format, unless the processor supports physical addresses greater
	than 32-bits, in which case a 2/1 format is recommended.
	
	Alternatively, the "ranges" property may be empty, indicating that the
	registers are visible on the parent bus using an identity mapping
	translation.  In other words, the parent bus address space is the same
	as the child bus address space.
	
	2) Note about "compatible" properties
	-------------------------------------
	
	These properties are optional, but recommended in devices and the root
	node. The format of a "compatible" property is a list of concatenated
	zero terminated strings. They allow a device to express its
	compatibility with a family of similar devices, in some cases,
	allowing a single driver to match against several devices regardless
	of their actual names.
	
	3) Note about "name" properties
	-------------------------------
	
	While earlier users of Open Firmware like OldWorld macintoshes tended
	to use the actual device name for the "name" property, it's nowadays
	considered a good practice to use a name that is closer to the device
	class (often equal to device_type). For example, nowadays, ethernet
	controllers are named "ethernet", an additional "model" property
	defining precisely the chip type/model, and "compatible" property
	defining the family in case a single driver can driver more than one
	of these chips. However, the kernel doesn't generally put any
	restriction on the "name" property; it is simply considered good
	practice to follow the standard and its evolutions as closely as
	possible.
	
	Note also that the new format version 16 makes the "name" property
	optional. If it's absent for a node, then the node's unit name is then
	used to reconstruct the name. That is, the part of the unit name
	before the "@" sign is used (or the entire unit name if no "@" sign
	is present).
	
	4) Note about node and property names and character set
	-------------------------------------------------------
	
	While open firmware provides more flexible usage of 8859-1, this
	specification enforces more strict rules. Nodes and properties should
	be comprised only of ASCII characters 'a' to 'z', '0' to
	'9', ',', '.', '_', '+', '#', '?', and '-'. Node names additionally
	allow uppercase characters 'A' to 'Z' (property names should be
	lowercase. The fact that vendors like Apple don't respect this rule is
	irrelevant here). Additionally, node and property names should always
	begin with a character in the range 'a' to 'z' (or 'A' to 'Z' for node
	names).
	
	The maximum number of characters for both nodes and property names
	is 31. In the case of node names, this is only the leftmost part of
	a unit name (the pure "name" property), it doesn't include the unit
	address which can extend beyond that limit.
	
	
	5) Required nodes and properties
	--------------------------------
	  These are all that are currently required. However, it is strongly
	  recommended that you expose PCI host bridges as documented in the
	  PCI binding to open firmware, and your interrupt tree as documented
	  in OF interrupt tree specification.
	
	  a) The root node
	
	  The root node requires some properties to be present:
	
	    - model : this is your board name/model
	    - #address-cells : address representation for "root" devices
	    - #size-cells: the size representation for "root" devices
	    - device_type : This property shouldn't be necessary. However, if
	      you decide to create a device_type for your root node, make sure it
	      is _not_ "chrp" unless your platform is a pSeries or PAPR compliant
	      one for 64-bit, or a CHRP-type machine for 32-bit as this will
	      matched by the kernel this way.
	
	  Additionally, some recommended properties are:
	
	    - compatible : the board "family" generally finds its way here,
	      for example, if you have 2 board models with a similar layout,
	      that typically get driven by the same platform code in the
	      kernel, you would use a different "model" property but put a
	      value in "compatible". The kernel doesn't directly use that
	      value but it is generally useful.
	
	  The root node is also generally where you add additional properties
	  specific to your board like the serial number if any, that sort of
	  thing. It is recommended that if you add any "custom" property whose
	  name may clash with standard defined ones, you prefix them with your
	  vendor name and a comma.
	
	  b) The /cpus node
	
	  This node is the parent of all individual CPU nodes. It doesn't
	  have any specific requirements, though it's generally good practice
	  to have at least:
	
	               #address-cells = <00000001>
	               #size-cells    = <00000000>
	
	  This defines that the "address" for a CPU is a single cell, and has
	  no meaningful size. This is not necessary but the kernel will assume
	  that format when reading the "reg" properties of a CPU node, see
	  below
	
	  c) The /cpus/* nodes
	
	  So under /cpus, you are supposed to create a node for every CPU on
	  the machine. There is no specific restriction on the name of the
	  CPU, though It's common practice to call it PowerPC,<name>. For
	  example, Apple uses PowerPC,G5 while IBM uses PowerPC,970FX.
	
	  Required properties:
	
	    - device_type : has to be "cpu"
	    - reg : This is the physical CPU number, it's a single 32-bit cell
	      and is also used as-is as the unit number for constructing the
	      unit name in the full path. For example, with 2 CPUs, you would
	      have the full path:
	        /cpus/PowerPC,970FX@0
	        /cpus/PowerPC,970FX@1
	      (unit addresses do not require leading zeroes)
	    - d-cache-block-size : one cell, L1 data cache block size in bytes (*)
	    - i-cache-block-size : one cell, L1 instruction cache block size in
	      bytes
	    - d-cache-size : one cell, size of L1 data cache in bytes
	    - i-cache-size : one cell, size of L1 instruction cache in bytes
	
	(*) The cache "block" size is the size on which the cache management
	instructions operate. Historically, this document used the cache
	"line" size here which is incorrect. The kernel will prefer the cache
	block size and will fallback to cache line size for backward
	compatibility.
	
	  Recommended properties:
	
	    - timebase-frequency : a cell indicating the frequency of the
	      timebase in Hz. This is not directly used by the generic code,
	      but you are welcome to copy/paste the pSeries code for setting
	      the kernel timebase/decrementer calibration based on this
	      value.
	    - clock-frequency : a cell indicating the CPU core clock frequency
	      in Hz. A new property will be defined for 64-bit values, but if
	      your frequency is < 4Ghz, one cell is enough. Here as well as
	      for the above, the common code doesn't use that property, but
	      you are welcome to re-use the pSeries or Maple one. A future
	      kernel version might provide a common function for this.
	    - d-cache-line-size : one cell, L1 data cache line size in bytes
	      if different from the block size
	    - i-cache-line-size : one cell, L1 instruction cache line size in
	      bytes if different from the block size
	
	  You are welcome to add any property you find relevant to your board,
	  like some information about the mechanism used to soft-reset the
	  CPUs. For example, Apple puts the GPIO number for CPU soft reset
	  lines in there as a "soft-reset" property since they start secondary
	  CPUs by soft-resetting them.
	
	
	  d) the /memory node(s)
	
	  To define the physical memory layout of your board, you should
	  create one or more memory node(s). You can either create a single
	  node with all memory ranges in its reg property, or you can create
	  several nodes, as you wish. The unit address (@ part) used for the
	  full path is the address of the first range of memory defined by a
	  given node. If you use a single memory node, this will typically be
	  @0.
	
	  Required properties:
	
	    - device_type : has to be "memory"
	    - reg : This property contains all the physical memory ranges of
	      your board. It's a list of addresses/sizes concatenated
	      together, with the number of cells of each defined by the
	      #address-cells and #size-cells of the root node. For example,
	      with both of these properties being 2 like in the example given
	      earlier, a 970 based machine with 6Gb of RAM could typically
	      have a "reg" property here that looks like:
	
	      00000000 00000000 00000000 80000000
	      00000001 00000000 00000001 00000000
	
	      That is a range starting at 0 of 0x80000000 bytes and a range
	      starting at 0x100000000 and of 0x100000000 bytes. You can see
	      that there is no memory covering the IO hole between 2Gb and
	      4Gb. Some vendors prefer splitting those ranges into smaller
	      segments, but the kernel doesn't care.
	
	  e) The /chosen node
	
	  This node is a bit "special". Normally, that's where open firmware
	  puts some variable environment information, like the arguments, or
	  the default input/output devices.
	
	  This specification makes a few of these mandatory, but also defines
	  some linux-specific properties that would be normally constructed by
	  the prom_init() trampoline when booting with an OF client interface,
	  but that you have to provide yourself when using the flattened format.
	
	  Recommended properties:
	
	    - bootargs : This zero-terminated string is passed as the kernel
	      command line
	    - linux,stdout-path : This is the full path to your standard
	      console device if any. Typically, if you have serial devices on
	      your board, you may want to put the full path to the one set as
	      the default console in the firmware here, for the kernel to pick
	      it up as its own default console. If you look at the function
	      set_preferred_console() in arch/ppc64/kernel/setup.c, you'll see
	      that the kernel tries to find out the default console and has
	      knowledge of various types like 8250 serial ports. You may want
	      to extend this function to add your own.
	
	  Note that u-boot creates and fills in the chosen node for platforms
	  that use it.
	
	  (Note: a practice that is now obsolete was to include a property
	  under /chosen called interrupt-controller which had a phandle value
	  that pointed to the main interrupt controller)
	
	  f) the /soc<SOCname> node
	
	  This node is used to represent a system-on-a-chip (SOC) and must be
	  present if the processor is a SOC. The top-level soc node contains
	  information that is global to all devices on the SOC. The node name
	  should contain a unit address for the SOC, which is the base address
	  of the memory-mapped register set for the SOC. The name of an soc
	  node should start with "soc", and the remainder of the name should
	  represent the part number for the soc.  For example, the MPC8540's
	  soc node would be called "soc8540".
	
	  Required properties:
	
	    - device_type : Should be "soc"
	    - ranges : Should be defined as specified in 1) to describe the
	      translation of SOC addresses for memory mapped SOC registers.
	    - bus-frequency: Contains the bus frequency for the SOC node.
	      Typically, the value of this field is filled in by the boot
	      loader.
	
	
	  Recommended properties:
	
	    - reg : This property defines the address and size of the
	      memory-mapped registers that are used for the SOC node itself.
	      It does not include the child device registers - these will be
	      defined inside each child node.  The address specified in the
	      "reg" property should match the unit address of the SOC node.
	    - #address-cells : Address representation for "soc" devices.  The
	      format of this field may vary depending on whether or not the
	      device registers are memory mapped.  For memory mapped
	      registers, this field represents the number of cells needed to
	      represent the address of the registers.  For SOCs that do not
	      use MMIO, a special address format should be defined that
	      contains enough cells to represent the required information.
	      See 1) above for more details on defining #address-cells.
	    - #size-cells : Size representation for "soc" devices
	    - #interrupt-cells : Defines the width of cells used to represent
	       interrupts.  Typically this value is <2>, which includes a
	       32-bit number that represents the interrupt number, and a
	       32-bit number that represents the interrupt sense and level.
	       This field is only needed if the SOC contains an interrupt
	       controller.
	
	  The SOC node may contain child nodes for each SOC device that the
	  platform uses.  Nodes should not be created for devices which exist
	  on the SOC but are not used by a particular platform. See chapter VI
	  for more information on how to specify devices that are part of a SOC.
	
	  Example SOC node for the MPC8540:
	
		soc8540@e0000000 {
			#address-cells = <1>;
			#size-cells = <1>;
			#interrupt-cells = <2>;
			device_type = "soc";
			ranges = <00000000 e0000000 00100000>
			reg = <e0000000 00003000>;
			bus-frequency = <0>;
		}
	
	
	
	IV - "dtc", the device tree compiler
	====================================
	
	
	dtc source code can be found at
	<http://git.jdl.com/gitweb/?p=dtc.git>
	
	WARNING: This version is still in early development stage; the
	resulting device-tree "blobs" have not yet been validated with the
	kernel. The current generated bloc lacks a useful reserve map (it will
	be fixed to generate an empty one, it's up to the bootloader to fill
	it up) among others. The error handling needs work, bugs are lurking,
	etc...
	
	dtc basically takes a device-tree in a given format and outputs a
	device-tree in another format. The currently supported formats are:
	
	  Input formats:
	  -------------
	
	     - "dtb": "blob" format, that is a flattened device-tree block
	       with
	        header all in a binary blob.
	     - "dts": "source" format. This is a text file containing a
	       "source" for a device-tree. The format is defined later in this
	        chapter.
	     - "fs" format. This is a representation equivalent to the
	        output of /proc/device-tree, that is nodes are directories and
		properties are files
	
	 Output formats:
	 ---------------
	
	     - "dtb": "blob" format
	     - "dts": "source" format
	     - "asm": assembly language file. This is a file that can be
	       sourced by gas to generate a device-tree "blob". That file can
	       then simply be added to your Makefile. Additionally, the
	       assembly file exports some symbols that can be used.
	
	
	The syntax of the dtc tool is
	
	    dtc [-I <input-format>] [-O <output-format>]
	        [-o output-filename] [-V output_version] input_filename
	
	
	The "output_version" defines what version of the "blob" format will be
	generated. Supported versions are 1,2,3 and 16. The default is
	currently version 3 but that may change in the future to version 16.
	
	Additionally, dtc performs various sanity checks on the tree, like the
	uniqueness of linux, phandle properties, validity of strings, etc...
	
	The format of the .dts "source" file is "C" like, supports C and C++
	style comments.
	
	/ {
	}
	
	The above is the "device-tree" definition. It's the only statement
	supported currently at the toplevel.
	
	/ {
	  property1 = "string_value";	/* define a property containing a 0
	                                 * terminated string
					 */
	
	  property2 = <1234abcd>;	/* define a property containing a
	                                 * numerical 32-bit value (hexadecimal)
					 */
	
	  property3 = <12345678 12345678 deadbeef>;
	                                /* define a property containing 3
	                                 * numerical 32-bit values (cells) in
	                                 * hexadecimal
					 */
	  property4 = [0a 0b 0c 0d de ea ad be ef];
	                                /* define a property whose content is
	                                 * an arbitrary array of bytes
	                                 */
	
	  childnode@addresss {	/* define a child node named "childnode"
	                                 * whose unit name is "childnode at
					 * address"
	                                 */
	
	    childprop = "hello\n";      /* define a property "childprop" of
	                                 * childnode (in this case, a string)
	                                 */
	  };
	};
	
	Nodes can contain other nodes etc... thus defining the hierarchical
	structure of the tree.
	
	Strings support common escape sequences from C: "\n", "\t", "\r",
	"\(octal value)", "\x(hex value)".
	
	It is also suggested that you pipe your source file through cpp (gcc
	preprocessor) so you can use #include's, #define for constants, etc...
	
	Finally, various options are planned but not yet implemented, like
	automatic generation of phandles, labels (exported to the asm file so
	you can point to a property content and change it easily from whatever
	you link the device-tree with), label or path instead of numeric value
	in some cells to "point" to a node (replaced by a phandle at compile
	time), export of reserve map address to the asm file, ability to
	specify reserve map content at compile time, etc...
	
	We may provide a .h include file with common definitions of that
	proves useful for some properties (like building PCI properties or
	interrupt maps) though it may be better to add a notion of struct
	definitions to the compiler...
	
	
	V - Recommendations for a bootloader
	====================================
	
	
	Here are some various ideas/recommendations that have been proposed
	while all this has been defined and implemented.
	
	  - The bootloader may want to be able to use the device-tree itself
	    and may want to manipulate it (to add/edit some properties,
	    like physical memory size or kernel arguments). At this point, 2
	    choices can be made. Either the bootloader works directly on the
	    flattened format, or the bootloader has its own internal tree
	    representation with pointers (similar to the kernel one) and
	    re-flattens the tree when booting the kernel. The former is a bit
	    more difficult to edit/modify, the later requires probably a bit
	    more code to handle the tree structure. Note that the structure
	    format has been designed so it's relatively easy to "insert"
	    properties or nodes or delete them by just memmoving things
	    around. It contains no internal offsets or pointers for this
	    purpose.
	
	  - An example of code for iterating nodes & retrieving properties
	    directly from the flattened tree format can be found in the kernel
	    file arch/ppc64/kernel/prom.c, look at scan_flat_dt() function,
	    its usage in early_init_devtree(), and the corresponding various
	    early_init_dt_scan_*() callbacks. That code can be re-used in a
	    GPL bootloader, and as the author of that code, I would be happy
	    to discuss possible free licensing to any vendor who wishes to
	    integrate all or part of this code into a non-GPL bootloader.
	
	
	
	VI - System-on-a-chip devices and nodes
	=======================================
	
	Many companies are now starting to develop system-on-a-chip
	processors, where the processor core (CPU) and many peripheral devices
	exist on a single piece of silicon.  For these SOCs, an SOC node
	should be used that defines child nodes for the devices that make
	up the SOC. While platforms are not required to use this model in
	order to boot the kernel, it is highly encouraged that all SOC
	implementations define as complete a flat-device-tree as possible to
	describe the devices on the SOC.  This will allow for the
	genericization of much of the kernel code.
	
	
	1) Defining child nodes of an SOC
	---------------------------------
	
	Each device that is part of an SOC may have its own node entry inside
	the SOC node.  For each device that is included in the SOC, the unit
	address property represents the address offset for this device's
	memory-mapped registers in the parent's address space.  The parent's
	address space is defined by the "ranges" property in the top-level soc
	node. The "reg" property for each node that exists directly under the
	SOC node should contain the address mapping from the child address space
	to the parent SOC address space and the size of the device's
	memory-mapped register file.
	
	For many devices that may exist inside an SOC, there are predefined
	specifications for the format of the device tree node.  All SOC child
	nodes should follow these specifications, except where noted in this
	document.
	
	See appendix A for an example partial SOC node definition for the
	MPC8540.
	
	
	2) Representing devices without a current OF specification
	----------------------------------------------------------
	
	Currently, there are many devices on SOCs that do not have a standard
	representation pre-defined as part of the open firmware
	specifications, mainly because the boards that contain these SOCs are
	not currently booted using open firmware.   This section contains
	descriptions for the SOC devices for which new nodes have been
	defined; this list will expand as more and more SOC-containing
	platforms are moved over to use the flattened-device-tree model.
	
	VII - Specifying interrupt information for devices
	===================================================
	
	The device tree represents the busses and devices of a hardware
	system in a form similar to the physical bus topology of the
	hardware.
	
	In addition, a logical 'interrupt tree' exists which represents the
	hierarchy and routing of interrupts in the hardware.
	
	The interrupt tree model is fully described in the
	document "Open Firmware Recommended Practice: Interrupt
	Mapping Version 0.9".  The document is available at:
	<http://playground.sun.com/1275/practice>.
	
	1) interrupts property
	----------------------
	
	Devices that generate interrupts to a single interrupt controller
	should use the conventional OF representation described in the
	OF interrupt mapping documentation.
	
	Each device which generates interrupts must have an 'interrupt'
	property.  The interrupt property value is an arbitrary number of
	of 'interrupt specifier' values which describe the interrupt or
	interrupts for the device.
	
	The encoding of an interrupt specifier is determined by the
	interrupt domain in which the device is located in the
	interrupt tree.  The root of an interrupt domain specifies in
	its #interrupt-cells property the number of 32-bit cells
	required to encode an interrupt specifier.  See the OF interrupt
	mapping documentation for a detailed description of domains.
	
	For example, the binding for the OpenPIC interrupt controller
	specifies  an #interrupt-cells value of 2 to encode the interrupt
	number and level/sense information. All interrupt children in an
	OpenPIC interrupt domain use 2 cells per interrupt in their interrupts
	property.
	
	The PCI bus binding specifies a #interrupt-cell value of 1 to encode
	which interrupt pin (INTA,INTB,INTC,INTD) is used.
	
	2) interrupt-parent property
	----------------------------
	
	The interrupt-parent property is specified to define an explicit
	link between a device node and its interrupt parent in
	the interrupt tree.  The value of interrupt-parent is the
	phandle of the parent node.
	
	If the interrupt-parent property is not defined for a node, its
	interrupt parent is assumed to be an ancestor in the node's
	_device tree_ hierarchy.
	
	3) OpenPIC Interrupt Controllers
	--------------------------------
	
	OpenPIC interrupt controllers require 2 cells to encode
	interrupt information.  The first cell defines the interrupt
	number.  The second cell defines the sense and level
	information.
	
	Sense and level information should be encoded as follows:
	
		0 = low to high edge sensitive type enabled
		1 = active low level sensitive type enabled
		2 = active high level sensitive type enabled
		3 = high to low edge sensitive type enabled
	
	4) ISA Interrupt Controllers
	----------------------------
	
	ISA PIC interrupt controllers require 2 cells to encode
	interrupt information.  The first cell defines the interrupt
	number.  The second cell defines the sense and level
	information.
	
	ISA PIC interrupt controllers should adhere to the ISA PIC
	encodings listed below:
	
		0 =  active low level sensitive type enabled
		1 =  active high level sensitive type enabled
		2 =  high to low edge sensitive type enabled
		3 =  low to high edge sensitive type enabled
	
	VIII - Specifying Device Power Management Information (sleep property)
	===================================================================
	
	Devices on SOCs often have mechanisms for placing devices into low-power
	states that are decoupled from the devices' own register blocks.  Sometimes,
	this information is more complicated than a cell-index property can
	reasonably describe.  Thus, each device controlled in such a manner
	may contain a "sleep" property which describes these connections.
	
	The sleep property consists of one or more sleep resources, each of
	which consists of a phandle to a sleep controller, followed by a
	controller-specific sleep specifier of zero or more cells.
	
	The semantics of what type of low power modes are possible are defined
	by the sleep controller.  Some examples of the types of low power modes
	that may be supported are:
	
	 - Dynamic: The device may be disabled or enabled at any time.
	 - System Suspend: The device may request to be disabled or remain
	   awake during system suspend, but will not be disabled until then.
	 - Permanent: The device is disabled permanently (until the next hard
	   reset).
	
	Some devices may share a clock domain with each other, such that they should
	only be suspended when none of the devices are in use.  Where reasonable,
	such nodes should be placed on a virtual bus, where the bus has the sleep
	property.  If the clock domain is shared among devices that cannot be
	reasonably grouped in this manner, then create a virtual sleep controller
	(similar to an interrupt nexus, except that defining a standardized
	sleep-map should wait until its necessity is demonstrated).
	
	Appendix A - Sample SOC node for MPC8540
	========================================
	
		soc@e0000000 {
			#address-cells = <1>;
			#size-cells = <1>;
			compatible = "fsl,mpc8540-ccsr", "simple-bus";
			device_type = "soc";
			ranges = <0x00000000 0xe0000000 0x00100000>
			bus-frequency = <0>;
			interrupt-parent = <&pic>;
	
			ethernet@24000 {
				#address-cells = <1>;
				#size-cells = <1>;
				device_type = "network";
				model = "TSEC";
				compatible = "gianfar", "simple-bus";
				reg = <0x24000 0x1000>;
				local-mac-address = [ 00 E0 0C 00 73 00 ];
				interrupts = <29 2 30 2 34 2>;
				phy-handle = <&phy0>;
				sleep = <&pmc 00000080>;
				ranges;
	
				mdio@24520 {
					reg = <0x24520 0x20>;
					compatible = "fsl,gianfar-mdio";
	
					phy0: ethernet-phy@0 {
						interrupts = <5 1>;
						reg = <0>;
						device_type = "ethernet-phy";
					};
	
					phy1: ethernet-phy@1 {
						interrupts = <5 1>;
						reg = <1>;
						device_type = "ethernet-phy";
					};
	
					phy3: ethernet-phy@3 {
						interrupts = <7 1>;
						reg = <3>;
						device_type = "ethernet-phy";
					};
				};
			};
	
			ethernet@25000 {
				device_type = "network";
				model = "TSEC";
				compatible = "gianfar";
				reg = <0x25000 0x1000>;
				local-mac-address = [ 00 E0 0C 00 73 01 ];
				interrupts = <13 2 14 2 18 2>;
				phy-handle = <&phy1>;
				sleep = <&pmc 00000040>;
			};
	
			ethernet@26000 {
				device_type = "network";
				model = "FEC";
				compatible = "gianfar";
				reg = <0x26000 0x1000>;
				local-mac-address = [ 00 E0 0C 00 73 02 ];
				interrupts = <41 2>;
				phy-handle = <&phy3>;
				sleep = <&pmc 00000020>;
			};
	
			serial@4500 {
				#address-cells = <1>;
				#size-cells = <1>;
				compatible = "fsl,mpc8540-duart", "simple-bus";
				sleep = <&pmc 00000002>;
				ranges;
	
				serial@4500 {
					device_type = "serial";
					compatible = "ns16550";
					reg = <0x4500 0x100>;
					clock-frequency = <0>;
					interrupts = <42 2>;
				};
	
				serial@4600 {
					device_type = "serial";
					compatible = "ns16550";
					reg = <0x4600 0x100>;
					clock-frequency = <0>;
					interrupts = <42 2>;
				};
			};
	
			pic: pic@40000 {
				interrupt-controller;
				#address-cells = <0>;
				#interrupt-cells = <2>;
				reg = <0x40000 0x40000>;
				compatible = "chrp,open-pic";
				device_type = "open-pic";
			};
	
			i2c@3000 {
				interrupts = <43 2>;
				reg = <0x3000 0x100>;
				compatible  = "fsl-i2c";
				dfsrr;
				sleep = <&pmc 00000004>;
			};
	
			pmc: power@e0070 {
				compatible = "fsl,mpc8540-pmc", "fsl,mpc8548-pmc";
				reg = <0xe0070 0x20>;
			};
		};

• [ powerpc ]
• 00-INDEX
• booting-without-of.txt
• bootwrapper.txt
• cpu_features.txt
• [ dts-bindings ]
• eeh-pci-error-recovery.txt
• hvcs.txt
• kvm_440.txt
• mpc52xx.txt
• phyp-assisted-dump.txt
• ptrace.txt
• qe_firmware.txt
• sound.txt
• zImage_layout.txt
•  

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