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1 Booting the Linux/ppc kernel without Open Firmware
2 --------------------------------------------------
4 (c) 2005 Benjamin Herrenschmidt <benh at kernel.crashing.org>,
5 IBM Corp.
6 (c) 2005 Becky Bruce <becky.bruce at freescale.com>,
7 Freescale Semiconductor, FSL SOC and 32-bit additions
8 (c) 2006 MontaVista Software, Inc.
9 Flash chip node definition
11 Table of Contents
12 =================
14 I - Introduction
15 1) Entry point for arch/powerpc
16 2) Board support
18 II - The DT block format
19 1) Header
20 2) Device tree generalities
21 3) Device tree "structure" block
22 4) Device tree "strings" block
24 III - Required content of the device tree
25 1) Note about cells and address representation
26 2) Note about "compatible" properties
27 3) Note about "name" properties
28 4) Note about node and property names and character set
29 5) Required nodes and properties
30 a) The root node
31 b) The /cpus node
32 c) The /cpus/* nodes
33 d) the /memory node(s)
34 e) The /chosen node
35 f) the /soc<SOCname> node
37 IV - "dtc", the device tree compiler
39 V - Recommendations for a bootloader
41 VI - System-on-a-chip devices and nodes
42 1) Defining child nodes of an SOC
43 2) Representing devices without a current OF specification
44 a) MDIO IO device
45 b) Gianfar-compatible ethernet nodes
46 c) PHY nodes
47 d) Interrupt controllers
48 e) I2C
49 f) Freescale SOC USB controllers
50 g) Freescale SOC SEC Security Engines
51 h) Board Control and Status (BCSR)
52 i) Freescale QUICC Engine module (QE)
53 j) Flash chip nodes
54 k) Global Utilities Block
56 VII - Specifying interrupt information for devices
57 1) interrupts property
58 2) interrupt-parent property
59 3) OpenPIC Interrupt Controllers
60 4) ISA Interrupt Controllers
62 Appendix A - Sample SOC node for MPC8540
65 Revision Information
66 ====================
68 May 18, 2005: Rev 0.1 - Initial draft, no chapter III yet.
70 May 19, 2005: Rev 0.2 - Add chapter III and bits & pieces here or
71 clarifies the fact that a lot of things are
72 optional, the kernel only requires a very
73 small device tree, though it is encouraged
74 to provide an as complete one as possible.
76 May 24, 2005: Rev 0.3 - Precise that DT block has to be in RAM
77 - Misc fixes
78 - Define version 3 and new format version 16
79 for the DT block (version 16 needs kernel
80 patches, will be fwd separately).
81 String block now has a size, and full path
82 is replaced by unit name for more
83 compactness.
84 linux,phandle is made optional, only nodes
85 that are referenced by other nodes need it.
86 "name" property is now automatically
87 deduced from the unit name
89 June 1, 2005: Rev 0.4 - Correct confusion between OF_DT_END and
90 OF_DT_END_NODE in structure definition.
91 - Change version 16 format to always align
92 property data to 4 bytes. Since tokens are
93 already aligned, that means no specific
94 required alignment between property size
95 and property data. The old style variable
96 alignment would make it impossible to do
97 "simple" insertion of properties using
98 memmove (thanks Milton for
99 noticing). Updated kernel patch as well
100 - Correct a few more alignment constraints
101 - Add a chapter about the device-tree
102 compiler and the textural representation of
103 the tree that can be "compiled" by dtc.
105 November 21, 2005: Rev 0.5
106 - Additions/generalizations for 32-bit
107 - Changed to reflect the new arch/powerpc
108 structure
109 - Added chapter VI
112 ToDo:
113 - Add some definitions of interrupt tree (simple/complex)
114 - Add some definitions for PCI host bridges
115 - Add some common address format examples
116 - Add definitions for standard properties and "compatible"
117 names for cells that are not already defined by the existing
118 OF spec.
119 - Compare FSL SOC use of PCI to standard and make sure no new
120 node definition required.
121 - Add more information about node definitions for SOC devices
122 that currently have no standard, like the FSL CPM.
125 I - Introduction
126 ================
128 During the recent development of the Linux/ppc64 kernel, and more
129 specifically, the addition of new platform types outside of the old
130 IBM pSeries/iSeries pair, it was decided to enforce some strict rules
131 regarding the kernel entry and bootloader <-> kernel interfaces, in
132 order to avoid the degeneration that had become the ppc32 kernel entry
133 point and the way a new platform should be added to the kernel. The
134 legacy iSeries platform breaks those rules as it predates this scheme,
135 but no new board support will be accepted in the main tree that
136 doesn't follows them properly. In addition, since the advent of the
137 arch/powerpc merged architecture for ppc32 and ppc64, new 32-bit
138 platforms and 32-bit platforms which move into arch/powerpc will be
139 required to use these rules as well.
141 The main requirement that will be defined in more detail below is
142 the presence of a device-tree whose format is defined after Open
143 Firmware specification. However, in order to make life easier
144 to embedded board vendors, the kernel doesn't require the device-tree
145 to represent every device in the system and only requires some nodes
146 and properties to be present. This will be described in detail in
147 section III, but, for example, the kernel does not require you to
148 create a node for every PCI device in the system. It is a requirement
149 to have a node for PCI host bridges in order to provide interrupt
150 routing informations and memory/IO ranges, among others. It is also
151 recommended to define nodes for on chip devices and other busses that
152 don't specifically fit in an existing OF specification. This creates a
153 great flexibility in the way the kernel can then probe those and match
154 drivers to device, without having to hard code all sorts of tables. It
155 also makes it more flexible for board vendors to do minor hardware
156 upgrades without significantly impacting the kernel code or cluttering
157 it with special cases.
160 1) Entry point for arch/powerpc
161 -------------------------------
163 There is one and one single entry point to the kernel, at the start
164 of the kernel image. That entry point supports two calling
165 conventions:
167 a) Boot from Open Firmware. If your firmware is compatible
168 with Open Firmware (IEEE 1275) or provides an OF compatible
169 client interface API (support for "interpret" callback of
170 forth words isn't required), you can enter the kernel with:
172 r5 : OF callback pointer as defined by IEEE 1275
173 bindings to powerpc. Only the 32-bit client interface
174 is currently supported
176 r3, r4 : address & length of an initrd if any or 0
178 The MMU is either on or off; the kernel will run the
179 trampoline located in arch/powerpc/kernel/prom_init.c to
180 extract the device-tree and other information from open
181 firmware and build a flattened device-tree as described
182 in b). prom_init() will then re-enter the kernel using
183 the second method. This trampoline code runs in the
184 context of the firmware, which is supposed to handle all
185 exceptions during that time.
187 b) Direct entry with a flattened device-tree block. This entry
188 point is called by a) after the OF trampoline and can also be
189 called directly by a bootloader that does not support the Open
190 Firmware client interface. It is also used by "kexec" to
191 implement "hot" booting of a new kernel from a previous
192 running one. This method is what I will describe in more
193 details in this document, as method a) is simply standard Open
194 Firmware, and thus should be implemented according to the
195 various standard documents defining it and its binding to the
196 PowerPC platform. The entry point definition then becomes:
198 r3 : physical pointer to the device-tree block
199 (defined in chapter II) in RAM
201 r4 : physical pointer to the kernel itself. This is
202 used by the assembly code to properly disable the MMU
203 in case you are entering the kernel with MMU enabled
204 and a non-1:1 mapping.
206 r5 : NULL (as to differentiate with method a)
208 Note about SMP entry: Either your firmware puts your other
209 CPUs in some sleep loop or spin loop in ROM where you can get
210 them out via a soft reset or some other means, in which case
211 you don't need to care, or you'll have to enter the kernel
212 with all CPUs. The way to do that with method b) will be
213 described in a later revision of this document.
216 2) Board support
217 ----------------
219 64-bit kernels:
221 Board supports (platforms) are not exclusive config options. An
222 arbitrary set of board supports can be built in a single kernel
223 image. The kernel will "know" what set of functions to use for a
224 given platform based on the content of the device-tree. Thus, you
225 should:
227 a) add your platform support as a _boolean_ option in
228 arch/powerpc/Kconfig, following the example of PPC_PSERIES,
229 PPC_PMAC and PPC_MAPLE. The later is probably a good
230 example of a board support to start from.
232 b) create your main platform file as
233 "arch/powerpc/platforms/myplatform/myboard_setup.c" and add it
234 to the Makefile under the condition of your CONFIG_
235 option. This file will define a structure of type "ppc_md"
236 containing the various callbacks that the generic code will
237 use to get to your platform specific code
239 c) Add a reference to your "ppc_md" structure in the
240 "machines" table in arch/powerpc/kernel/setup_64.c if you are
241 a 64-bit platform.
243 d) request and get assigned a platform number (see PLATFORM_*
244 constants in include/asm-powerpc/processor.h
246 32-bit embedded kernels:
248 Currently, board support is essentially an exclusive config option.
249 The kernel is configured for a single platform. Part of the reason
250 for this is to keep kernels on embedded systems small and efficient;
251 part of this is due to the fact the code is already that way. In the
252 future, a kernel may support multiple platforms, but only if the
253 platforms feature the same core architecture. A single kernel build
254 cannot support both configurations with Book E and configurations
255 with classic Powerpc architectures.
257 32-bit embedded platforms that are moved into arch/powerpc using a
258 flattened device tree should adopt the merged tree practice of
259 setting ppc_md up dynamically, even though the kernel is currently
260 built with support for only a single platform at a time. This allows
261 unification of the setup code, and will make it easier to go to a
262 multiple-platform-support model in the future.
264 NOTE: I believe the above will be true once Ben's done with the merge
265 of the boot sequences.... someone speak up if this is wrong!
267 To add a 32-bit embedded platform support, follow the instructions
268 for 64-bit platforms above, with the exception that the Kconfig
269 option should be set up such that the kernel builds exclusively for
270 the platform selected. The processor type for the platform should
271 enable another config option to select the specific board
272 supported.
274 NOTE: If Ben doesn't merge the setup files, may need to change this to
275 point to setup_32.c
278 I will describe later the boot process and various callbacks that
279 your platform should implement.
282 II - The DT block format
283 ========================
286 This chapter defines the actual format of the flattened device-tree
287 passed to the kernel. The actual content of it and kernel requirements
288 are described later. You can find example of code manipulating that
289 format in various places, including arch/powerpc/kernel/prom_init.c
290 which will generate a flattened device-tree from the Open Firmware
291 representation, or the fs2dt utility which is part of the kexec tools
292 which will generate one from a filesystem representation. It is
293 expected that a bootloader like uboot provides a bit more support,
294 that will be discussed later as well.
296 Note: The block has to be in main memory. It has to be accessible in
297 both real mode and virtual mode with no mapping other than main
298 memory. If you are writing a simple flash bootloader, it should copy
299 the block to RAM before passing it to the kernel.
302 1) Header
303 ---------
305 The kernel is entered with r3 pointing to an area of memory that is
306 roughly described in include/asm-powerpc/prom.h by the structure
307 boot_param_header:
309 struct boot_param_header {
310 u32 magic; /* magic word OF_DT_HEADER */
311 u32 totalsize; /* total size of DT block */
312 u32 off_dt_struct; /* offset to structure */
313 u32 off_dt_strings; /* offset to strings */
314 u32 off_mem_rsvmap; /* offset to memory reserve map
315 */
316 u32 version; /* format version */
317 u32 last_comp_version; /* last compatible version */
319 /* version 2 fields below */
320 u32 boot_cpuid_phys; /* Which physical CPU id we're
321 booting on */
322 /* version 3 fields below */
323 u32 size_dt_strings; /* size of the strings block */
325 /* version 17 fields below */
326 u32 size_dt_struct; /* size of the DT structure block */
327 };
329 Along with the constants:
331 /* Definitions used by the flattened device tree */
332 #define OF_DT_HEADER 0xd00dfeed /* 4: version,
333 4: total size */
334 #define OF_DT_BEGIN_NODE 0x1 /* Start node: full name
335 */
336 #define OF_DT_END_NODE 0x2 /* End node */
337 #define OF_DT_PROP 0x3 /* Property: name off,
338 size, content */
339 #define OF_DT_END 0x9
341 All values in this header are in big endian format, the various
342 fields in this header are defined more precisely below. All
343 "offset" values are in bytes from the start of the header; that is
344 from the value of r3.
346 - magic
348 This is a magic value that "marks" the beginning of the
349 device-tree block header. It contains the value 0xd00dfeed and is
350 defined by the constant OF_DT_HEADER
352 - totalsize
354 This is the total size of the DT block including the header. The
355 "DT" block should enclose all data structures defined in this
356 chapter (who are pointed to by offsets in this header). That is,
357 the device-tree structure, strings, and the memory reserve map.
359 - off_dt_struct
361 This is an offset from the beginning of the header to the start
362 of the "structure" part the device tree. (see 2) device tree)
364 - off_dt_strings
366 This is an offset from the beginning of the header to the start
367 of the "strings" part of the device-tree
369 - off_mem_rsvmap
371 This is an offset from the beginning of the header to the start
372 of the reserved memory map. This map is a list of pairs of 64-
373 bit integers. Each pair is a physical address and a size. The
374 list is terminated by an entry of size 0. This map provides the
375 kernel with a list of physical memory areas that are "reserved"
376 and thus not to be used for memory allocations, especially during
377 early initialization. The kernel needs to allocate memory during
378 boot for things like un-flattening the device-tree, allocating an
379 MMU hash table, etc... Those allocations must be done in such a
380 way to avoid overriding critical things like, on Open Firmware
381 capable machines, the RTAS instance, or on some pSeries, the TCE
382 tables used for the iommu. Typically, the reserve map should
383 contain _at least_ this DT block itself (header,total_size). If
384 you are passing an initrd to the kernel, you should reserve it as
385 well. You do not need to reserve the kernel image itself. The map
386 should be 64-bit aligned.
388 - version
390 This is the version of this structure. Version 1 stops
391 here. Version 2 adds an additional field boot_cpuid_phys.
392 Version 3 adds the size of the strings block, allowing the kernel
393 to reallocate it easily at boot and free up the unused flattened
394 structure after expansion. Version 16 introduces a new more
395 "compact" format for the tree itself that is however not backward
396 compatible. Version 17 adds an additional field, size_dt_struct,
397 allowing it to be reallocated or moved more easily (this is
398 particularly useful for bootloaders which need to make
399 adjustments to a device tree based on probed information). You
400 should always generate a structure of the highest version defined
401 at the time of your implementation. Currently that is version 17,
402 unless you explicitly aim at being backward compatible.
404 - last_comp_version
406 Last compatible version. This indicates down to what version of
407 the DT block you are backward compatible. For example, version 2
408 is backward compatible with version 1 (that is, a kernel build
409 for version 1 will be able to boot with a version 2 format). You
410 should put a 1 in this field if you generate a device tree of
411 version 1 to 3, or 16 if you generate a tree of version 16 or 17
412 using the new unit name format.
414 - boot_cpuid_phys
416 This field only exist on version 2 headers. It indicate which
417 physical CPU ID is calling the kernel entry point. This is used,
418 among others, by kexec. If you are on an SMP system, this value
419 should match the content of the "reg" property of the CPU node in
420 the device-tree corresponding to the CPU calling the kernel entry
421 point (see further chapters for more informations on the required
422 device-tree contents)
424 - size_dt_strings
426 This field only exists on version 3 and later headers. It
427 gives the size of the "strings" section of the device tree (which
428 starts at the offset given by off_dt_strings).
430 - size_dt_struct
432 This field only exists on version 17 and later headers. It gives
433 the size of the "structure" section of the device tree (which
434 starts at the offset given by off_dt_struct).
436 So the typical layout of a DT block (though the various parts don't
437 need to be in that order) looks like this (addresses go from top to
438 bottom):
441 ------------------------------
442 r3 -> | struct boot_param_header |
443 ------------------------------
444 | (alignment gap) (*) |
445 ------------------------------
446 | memory reserve map |
447 ------------------------------
448 | (alignment gap) |
449 ------------------------------
450 | |
451 | device-tree structure |
452 | |
453 ------------------------------
454 | (alignment gap) |
455 ------------------------------
456 | |
457 | device-tree strings |
458 | |
459 -----> ------------------------------
460 |
461 |
462 --- (r3 + totalsize)
464 (*) The alignment gaps are not necessarily present; their presence
465 and size are dependent on the various alignment requirements of
466 the individual data blocks.
469 2) Device tree generalities
470 ---------------------------
472 This device-tree itself is separated in two different blocks, a
473 structure block and a strings block. Both need to be aligned to a 4
474 byte boundary.
476 First, let's quickly describe the device-tree concept before detailing
477 the storage format. This chapter does _not_ describe the detail of the
478 required types of nodes & properties for the kernel, this is done
479 later in chapter III.
481 The device-tree layout is strongly inherited from the definition of
482 the Open Firmware IEEE 1275 device-tree. It's basically a tree of
483 nodes, each node having two or more named properties. A property can
484 have a value or not.
486 It is a tree, so each node has one and only one parent except for the
487 root node who has no parent.
489 A node has 2 names. The actual node name is generally contained in a
490 property of type "name" in the node property list whose value is a
491 zero terminated string and is mandatory for version 1 to 3 of the
492 format definition (as it is in Open Firmware). Version 16 makes it
493 optional as it can generate it from the unit name defined below.
495 There is also a "unit name" that is used to differentiate nodes with
496 the same name at the same level, it is usually made of the node
497 names, the "@" sign, and a "unit address", which definition is
498 specific to the bus type the node sits on.
500 The unit name doesn't exist as a property per-se but is included in
501 the device-tree structure. It is typically used to represent "path" in
502 the device-tree. More details about the actual format of these will be
503 below.
505 The kernel powerpc generic code does not make any formal use of the
506 unit address (though some board support code may do) so the only real
507 requirement here for the unit address is to ensure uniqueness of
508 the node unit name at a given level of the tree. Nodes with no notion
509 of address and no possible sibling of the same name (like /memory or
510 /cpus) may omit the unit address in the context of this specification,
511 or use the "@0" default unit address. The unit name is used to define
512 a node "full path", which is the concatenation of all parent node
513 unit names separated with "/".
515 The root node doesn't have a defined name, and isn't required to have
516 a name property either if you are using version 3 or earlier of the
517 format. It also has no unit address (no @ symbol followed by a unit
518 address). The root node unit name is thus an empty string. The full
519 path to the root node is "/".
521 Every node which actually represents an actual device (that is, a node
522 which isn't only a virtual "container" for more nodes, like "/cpus"
523 is) is also required to have a "device_type" property indicating the
524 type of node .
526 Finally, every node that can be referenced from a property in another
527 node is required to have a "linux,phandle" property. Real open
528 firmware implementations provide a unique "phandle" value for every
529 node that the "prom_init()" trampoline code turns into
530 "linux,phandle" properties. However, this is made optional if the
531 flattened device tree is used directly. An example of a node
532 referencing another node via "phandle" is when laying out the
533 interrupt tree which will be described in a further version of this
534 document.
536 This "linux, phandle" property is a 32-bit value that uniquely
537 identifies a node. You are free to use whatever values or system of
538 values, internal pointers, or whatever to generate these, the only
539 requirement is that every node for which you provide that property has
540 a unique value for it.
542 Here is an example of a simple device-tree. In this example, an "o"
543 designates a node followed by the node unit name. Properties are
544 presented with their name followed by their content. "content"
545 represents an ASCII string (zero terminated) value, while <content>
546 represents a 32-bit hexadecimal value. The various nodes in this
547 example will be discussed in a later chapter. At this point, it is
548 only meant to give you a idea of what a device-tree looks like. I have
549 purposefully kept the "name" and "linux,phandle" properties which
550 aren't necessary in order to give you a better idea of what the tree
551 looks like in practice.
553 / o device-tree
554 |- name = "device-tree"
555 |- model = "MyBoardName"
556 |- compatible = "MyBoardFamilyName"
557 |- #address-cells = <2>
558 |- #size-cells = <2>
559 |- linux,phandle = <0>
560 |
561 o cpus
562 | | - name = "cpus"
563 | | - linux,phandle = <1>
564 | | - #address-cells = <1>
565 | | - #size-cells = <0>
566 | |
567 | o PowerPC,970@0
568 | |- name = "PowerPC,970"
569 | |- device_type = "cpu"
570 | |- reg = <0>
571 | |- clock-frequency = <5f5e1000>
572 | |- 64-bit
573 | |- linux,phandle = <2>
574 |
575 o memory@0
576 | |- name = "memory"
577 | |- device_type = "memory"
578 | |- reg = <00000000 00000000 00000000 20000000>
579 | |- linux,phandle = <3>
580 |
581 o chosen
582 |- name = "chosen"
583 |- bootargs = "root=/dev/sda2"
584 |- linux,phandle = <4>
586 This tree is almost a minimal tree. It pretty much contains the
587 minimal set of required nodes and properties to boot a linux kernel;
588 that is, some basic model informations at the root, the CPUs, and the
589 physical memory layout. It also includes misc information passed
590 through /chosen, like in this example, the platform type (mandatory)
591 and the kernel command line arguments (optional).
593 The /cpus/PowerPC,970@0/64-bit property is an example of a
594 property without a value. All other properties have a value. The
595 significance of the #address-cells and #size-cells properties will be
596 explained in chapter IV which defines precisely the required nodes and
597 properties and their content.
600 3) Device tree "structure" block
602 The structure of the device tree is a linearized tree structure. The
603 "OF_DT_BEGIN_NODE" token starts a new node, and the "OF_DT_END_NODE"
604 ends that node definition. Child nodes are simply defined before
605 "OF_DT_END_NODE" (that is nodes within the node). A 'token' is a 32
606 bit value. The tree has to be "finished" with a OF_DT_END token
608 Here's the basic structure of a single node:
610 * token OF_DT_BEGIN_NODE (that is 0x00000001)
611 * for version 1 to 3, this is the node full path as a zero
612 terminated string, starting with "/". For version 16 and later,
613 this is the node unit name only (or an empty string for the
614 root node)
615 * [align gap to next 4 bytes boundary]
616 * for each property:
617 * token OF_DT_PROP (that is 0x00000003)
618 * 32-bit value of property value size in bytes (or 0 if no
619 value)
620 * 32-bit value of offset in string block of property name
621 * property value data if any
622 * [align gap to next 4 bytes boundary]
623 * [child nodes if any]
624 * token OF_DT_END_NODE (that is 0x00000002)
626 So the node content can be summarized as a start token, a full path,
627 a list of properties, a list of child nodes, and an end token. Every
628 child node is a full node structure itself as defined above.
630 NOTE: The above definition requires that all property definitions for
631 a particular node MUST precede any subnode definitions for that node.
632 Although the structure would not be ambiguous if properties and
633 subnodes were intermingled, the kernel parser requires that the
634 properties come first (up until at least 2.6.22). Any tools
635 manipulating a flattened tree must take care to preserve this
636 constraint.
638 4) Device tree "strings" block
640 In order to save space, property names, which are generally redundant,
641 are stored separately in the "strings" block. This block is simply the
642 whole bunch of zero terminated strings for all property names
643 concatenated together. The device-tree property definitions in the
644 structure block will contain offset values from the beginning of the
645 strings block.
648 III - Required content of the device tree
649 =========================================
651 WARNING: All "linux,*" properties defined in this document apply only
652 to a flattened device-tree. If your platform uses a real
653 implementation of Open Firmware or an implementation compatible with
654 the Open Firmware client interface, those properties will be created
655 by the trampoline code in the kernel's prom_init() file. For example,
656 that's where you'll have to add code to detect your board model and
657 set the platform number. However, when using the flattened device-tree
658 entry point, there is no prom_init() pass, and thus you have to
659 provide those properties yourself.
662 1) Note about cells and address representation
663 ----------------------------------------------
665 The general rule is documented in the various Open Firmware
666 documentations. If you choose to describe a bus with the device-tree
667 and there exist an OF bus binding, then you should follow the
668 specification. However, the kernel does not require every single
669 device or bus to be described by the device tree.
671 In general, the format of an address for a device is defined by the
672 parent bus type, based on the #address-cells and #size-cells
673 property. In the absence of such a property, the parent's parent
674 values are used, etc... The kernel requires the root node to have
675 those properties defining addresses format for devices directly mapped
676 on the processor bus.
678 Those 2 properties define 'cells' for representing an address and a
679 size. A "cell" is a 32-bit number. For example, if both contain 2
680 like the example tree given above, then an address and a size are both
681 composed of 2 cells, and each is a 64-bit number (cells are
682 concatenated and expected to be in big endian format). Another example
683 is the way Apple firmware defines them, with 2 cells for an address
684 and one cell for a size. Most 32-bit implementations should define
685 #address-cells and #size-cells to 1, which represents a 32-bit value.
686 Some 32-bit processors allow for physical addresses greater than 32
687 bits; these processors should define #address-cells as 2.
689 "reg" properties are always a tuple of the type "address size" where
690 the number of cells of address and size is specified by the bus
691 #address-cells and #size-cells. When a bus supports various address
692 spaces and other flags relative to a given address allocation (like
693 prefetchable, etc...) those flags are usually added to the top level
694 bits of the physical address. For example, a PCI physical address is
695 made of 3 cells, the bottom two containing the actual address itself
696 while the top cell contains address space indication, flags, and pci
697 bus & device numbers.
699 For busses that support dynamic allocation, it's the accepted practice
700 to then not provide the address in "reg" (keep it 0) though while
701 providing a flag indicating the address is dynamically allocated, and
702 then, to provide a separate "assigned-addresses" property that
703 contains the fully allocated addresses. See the PCI OF bindings for
704 details.
706 In general, a simple bus with no address space bits and no dynamic
707 allocation is preferred if it reflects your hardware, as the existing
708 kernel address parsing functions will work out of the box. If you
709 define a bus type with a more complex address format, including things
710 like address space bits, you'll have to add a bus translator to the
711 prom_parse.c file of the recent kernels for your bus type.
713 The "reg" property only defines addresses and sizes (if #size-cells
714 is non-0) within a given bus. In order to translate addresses upward
715 (that is into parent bus addresses, and possibly into CPU physical
716 addresses), all busses must contain a "ranges" property. If the
717 "ranges" property is missing at a given level, it's assumed that
718 translation isn't possible. The format of the "ranges" property for a
719 bus is a list of:
721 bus address, parent bus address, size
723 "bus address" is in the format of the bus this bus node is defining,
724 that is, for a PCI bridge, it would be a PCI address. Thus, (bus
725 address, size) defines a range of addresses for child devices. "parent
726 bus address" is in the format of the parent bus of this bus. For
727 example, for a PCI host controller, that would be a CPU address. For a
728 PCI<->ISA bridge, that would be a PCI address. It defines the base
729 address in the parent bus where the beginning of that range is mapped.
731 For a new 64-bit powerpc board, I recommend either the 2/2 format or
732 Apple's 2/1 format which is slightly more compact since sizes usually
733 fit in a single 32-bit word. New 32-bit powerpc boards should use a
734 1/1 format, unless the processor supports physical addresses greater
735 than 32-bits, in which case a 2/1 format is recommended.
738 2) Note about "compatible" properties
739 -------------------------------------
741 These properties are optional, but recommended in devices and the root
742 node. The format of a "compatible" property is a list of concatenated
743 zero terminated strings. They allow a device to express its
744 compatibility with a family of similar devices, in some cases,
745 allowing a single driver to match against several devices regardless
746 of their actual names.
748 3) Note about "name" properties
749 -------------------------------
751 While earlier users of Open Firmware like OldWorld macintoshes tended
752 to use the actual device name for the "name" property, it's nowadays
753 considered a good practice to use a name that is closer to the device
754 class (often equal to device_type). For example, nowadays, ethernet
755 controllers are named "ethernet", an additional "model" property
756 defining precisely the chip type/model, and "compatible" property
757 defining the family in case a single driver can driver more than one
758 of these chips. However, the kernel doesn't generally put any
759 restriction on the "name" property; it is simply considered good
760 practice to follow the standard and its evolutions as closely as
761 possible.
763 Note also that the new format version 16 makes the "name" property
764 optional. If it's absent for a node, then the node's unit name is then
765 used to reconstruct the name. That is, the part of the unit name
766 before the "@" sign is used (or the entire unit name if no "@" sign
767 is present).
769 4) Note about node and property names and character set
770 -------------------------------------------------------
772 While open firmware provides more flexible usage of 8859-1, this
773 specification enforces more strict rules. Nodes and properties should
774 be comprised only of ASCII characters 'a' to 'z', '0' to
775 '9', ',', '.', '_', '+', '#', '?', and '-'. Node names additionally
776 allow uppercase characters 'A' to 'Z' (property names should be
777 lowercase. The fact that vendors like Apple don't respect this rule is
778 irrelevant here). Additionally, node and property names should always
779 begin with a character in the range 'a' to 'z' (or 'A' to 'Z' for node
780 names).
782 The maximum number of characters for both nodes and property names
783 is 31. In the case of node names, this is only the leftmost part of
784 a unit name (the pure "name" property), it doesn't include the unit
785 address which can extend beyond that limit.
788 5) Required nodes and properties
789 --------------------------------
790 These are all that are currently required. However, it is strongly
791 recommended that you expose PCI host bridges as documented in the
792 PCI binding to open firmware, and your interrupt tree as documented
793 in OF interrupt tree specification.
795 a) The root node
797 The root node requires some properties to be present:
799 - model : this is your board name/model
800 - #address-cells : address representation for "root" devices
801 - #size-cells: the size representation for "root" devices
802 - device_type : This property shouldn't be necessary. However, if
803 you decide to create a device_type for your root node, make sure it
804 is _not_ "chrp" unless your platform is a pSeries or PAPR compliant
805 one for 64-bit, or a CHRP-type machine for 32-bit as this will
806 matched by the kernel this way.
808 Additionally, some recommended properties are:
810 - compatible : the board "family" generally finds its way here,
811 for example, if you have 2 board models with a similar layout,
812 that typically get driven by the same platform code in the
813 kernel, you would use a different "model" property but put a
814 value in "compatible". The kernel doesn't directly use that
815 value but it is generally useful.
817 The root node is also generally where you add additional properties
818 specific to your board like the serial number if any, that sort of
819 thing. It is recommended that if you add any "custom" property whose
820 name may clash with standard defined ones, you prefix them with your
821 vendor name and a comma.
823 b) The /cpus node
825 This node is the parent of all individual CPU nodes. It doesn't
826 have any specific requirements, though it's generally good practice
827 to have at least:
829 #address-cells = <00000001>
830 #size-cells = <00000000>
832 This defines that the "address" for a CPU is a single cell, and has
833 no meaningful size. This is not necessary but the kernel will assume
834 that format when reading the "reg" properties of a CPU node, see
835 below
837 c) The /cpus/* nodes
839 So under /cpus, you are supposed to create a node for every CPU on
840 the machine. There is no specific restriction on the name of the
841 CPU, though It's common practice to call it PowerPC,<name>. For
842 example, Apple uses PowerPC,G5 while IBM uses PowerPC,970FX.
844 Required properties:
846 - device_type : has to be "cpu"
847 - reg : This is the physical CPU number, it's a single 32-bit cell
848 and is also used as-is as the unit number for constructing the
849 unit name in the full path. For example, with 2 CPUs, you would
850 have the full path:
851 /cpus/PowerPC,970FX@0
852 /cpus/PowerPC,970FX@1
853 (unit addresses do not require leading zeroes)
854 - d-cache-line-size : one cell, L1 data cache line size in bytes
855 - i-cache-line-size : one cell, L1 instruction cache line size in
856 bytes
857 - d-cache-size : one cell, size of L1 data cache in bytes
858 - i-cache-size : one cell, size of L1 instruction cache in bytes
860 Recommended properties:
862 - timebase-frequency : a cell indicating the frequency of the
863 timebase in Hz. This is not directly used by the generic code,
864 but you are welcome to copy/paste the pSeries code for setting
865 the kernel timebase/decrementer calibration based on this
866 value.
867 - clock-frequency : a cell indicating the CPU core clock frequency
868 in Hz. A new property will be defined for 64-bit values, but if
869 your frequency is < 4Ghz, one cell is enough. Here as well as
870 for the above, the common code doesn't use that property, but
871 you are welcome to re-use the pSeries or Maple one. A future
872 kernel version might provide a common function for this.
874 You are welcome to add any property you find relevant to your board,
875 like some information about the mechanism used to soft-reset the
876 CPUs. For example, Apple puts the GPIO number for CPU soft reset
877 lines in there as a "soft-reset" property since they start secondary
878 CPUs by soft-resetting them.
881 d) the /memory node(s)
883 To define the physical memory layout of your board, you should
884 create one or more memory node(s). You can either create a single
885 node with all memory ranges in its reg property, or you can create
886 several nodes, as you wish. The unit address (@ part) used for the
887 full path is the address of the first range of memory defined by a
888 given node. If you use a single memory node, this will typically be
889 @0.
891 Required properties:
893 - device_type : has to be "memory"
894 - reg : This property contains all the physical memory ranges of
895 your board. It's a list of addresses/sizes concatenated
896 together, with the number of cells of each defined by the
897 #address-cells and #size-cells of the root node. For example,
898 with both of these properties being 2 like in the example given
899 earlier, a 970 based machine with 6Gb of RAM could typically
900 have a "reg" property here that looks like:
902 00000000 00000000 00000000 80000000
903 00000001 00000000 00000001 00000000
905 That is a range starting at 0 of 0x80000000 bytes and a range
906 starting at 0x100000000 and of 0x100000000 bytes. You can see
907 that there is no memory covering the IO hole between 2Gb and
908 4Gb. Some vendors prefer splitting those ranges into smaller
909 segments, but the kernel doesn't care.
911 e) The /chosen node
913 This node is a bit "special". Normally, that's where open firmware
914 puts some variable environment information, like the arguments, or
915 the default input/output devices.
917 This specification makes a few of these mandatory, but also defines
918 some linux-specific properties that would be normally constructed by
919 the prom_init() trampoline when booting with an OF client interface,
920 but that you have to provide yourself when using the flattened format.
922 Recommended properties:
924 - bootargs : This zero-terminated string is passed as the kernel
925 command line
926 - linux,stdout-path : This is the full path to your standard
927 console device if any. Typically, if you have serial devices on
928 your board, you may want to put the full path to the one set as
929 the default console in the firmware here, for the kernel to pick
930 it up as its own default console. If you look at the function
931 set_preferred_console() in arch/ppc64/kernel/setup.c, you'll see
932 that the kernel tries to find out the default console and has
933 knowledge of various types like 8250 serial ports. You may want
934 to extend this function to add your own.
936 Note that u-boot creates and fills in the chosen node for platforms
937 that use it.
939 (Note: a practice that is now obsolete was to include a property
940 under /chosen called interrupt-controller which had a phandle value
941 that pointed to the main interrupt controller)
943 f) the /soc<SOCname> node
945 This node is used to represent a system-on-a-chip (SOC) and must be
946 present if the processor is a SOC. The top-level soc node contains
947 information that is global to all devices on the SOC. The node name
948 should contain a unit address for the SOC, which is the base address
949 of the memory-mapped register set for the SOC. The name of an soc
950 node should start with "soc", and the remainder of the name should
951 represent the part number for the soc. For example, the MPC8540's
952 soc node would be called "soc8540".
954 Required properties:
956 - device_type : Should be "soc"
957 - ranges : Should be defined as specified in 1) to describe the
958 translation of SOC addresses for memory mapped SOC registers.
959 - bus-frequency: Contains the bus frequency for the SOC node.
960 Typically, the value of this field is filled in by the boot
961 loader.
964 Recommended properties:
966 - reg : This property defines the address and size of the
967 memory-mapped registers that are used for the SOC node itself.
968 It does not include the child device registers - these will be
969 defined inside each child node. The address specified in the
970 "reg" property should match the unit address of the SOC node.
971 - #address-cells : Address representation for "soc" devices. The
972 format of this field may vary depending on whether or not the
973 device registers are memory mapped. For memory mapped
974 registers, this field represents the number of cells needed to
975 represent the address of the registers. For SOCs that do not
976 use MMIO, a special address format should be defined that
977 contains enough cells to represent the required information.
978 See 1) above for more details on defining #address-cells.
979 - #size-cells : Size representation for "soc" devices
980 - #interrupt-cells : Defines the width of cells used to represent
981 interrupts. Typically this value is <2>, which includes a
982 32-bit number that represents the interrupt number, and a
983 32-bit number that represents the interrupt sense and level.
984 This field is only needed if the SOC contains an interrupt
985 controller.
987 The SOC node may contain child nodes for each SOC device that the
988 platform uses. Nodes should not be created for devices which exist
989 on the SOC but are not used by a particular platform. See chapter VI
990 for more information on how to specify devices that are part of a SOC.
992 Example SOC node for the MPC8540:
994 soc8540@e0000000 {
995 #address-cells = <1>;
996 #size-cells = <1>;
997 #interrupt-cells = <2>;
998 device_type = "soc";
999 ranges = <00000000 e0000000 00100000>
1000 reg = <e0000000 00003000>;
1001 bus-frequency = <0>;
1002 }
1006 IV - "dtc", the device tree compiler
1007 ====================================
1010 dtc source code can be found at
1011 <http://ozlabs.org/~dgibson/dtc/dtc.tar.gz>
1013 WARNING: This version is still in early development stage; the
1014 resulting device-tree "blobs" have not yet been validated with the
1015 kernel. The current generated bloc lacks a useful reserve map (it will
1016 be fixed to generate an empty one, it's up to the bootloader to fill
1017 it up) among others. The error handling needs work, bugs are lurking,
1018 etc...
1020 dtc basically takes a device-tree in a given format and outputs a
1021 device-tree in another format. The currently supported formats are:
1023 Input formats:
1024 -------------
1026 - "dtb": "blob" format, that is a flattened device-tree block
1027 with
1028 header all in a binary blob.
1029 - "dts": "source" format. This is a text file containing a
1030 "source" for a device-tree. The format is defined later in this
1031 chapter.
1032 - "fs" format. This is a representation equivalent to the
1033 output of /proc/device-tree, that is nodes are directories and
1034 properties are files
1036 Output formats:
1037 ---------------
1039 - "dtb": "blob" format
1040 - "dts": "source" format
1041 - "asm": assembly language file. This is a file that can be
1042 sourced by gas to generate a device-tree "blob". That file can
1043 then simply be added to your Makefile. Additionally, the
1044 assembly file exports some symbols that can be used.
1047 The syntax of the dtc tool is
1049 dtc [-I <input-format>] [-O <output-format>]
1050 [-o output-filename] [-V output_version] input_filename
1053 The "output_version" defines what version of the "blob" format will be
1054 generated. Supported versions are 1,2,3 and 16. The default is
1055 currently version 3 but that may change in the future to version 16.
1057 Additionally, dtc performs various sanity checks on the tree, like the
1058 uniqueness of linux, phandle properties, validity of strings, etc...
1060 The format of the .dts "source" file is "C" like, supports C and C++
1061 style comments.
1063 / {
1064 }
1066 The above is the "device-tree" definition. It's the only statement
1067 supported currently at the toplevel.
1069 / {
1070 property1 = "string_value"; /* define a property containing a 0
1071 * terminated string
1072 */
1074 property2 = <1234abcd>; /* define a property containing a
1075 * numerical 32-bit value (hexadecimal)
1076 */
1078 property3 = <12345678 12345678 deadbeef>;
1079 /* define a property containing 3
1080 * numerical 32-bit values (cells) in
1081 * hexadecimal
1082 */
1083 property4 = [0a 0b 0c 0d de ea ad be ef];
1084 /* define a property whose content is
1085 * an arbitrary array of bytes
1086 */
1088 childnode@addresss { /* define a child node named "childnode"
1089 * whose unit name is "childnode at
1090 * address"
1091 */
1093 childprop = "hello\n"; /* define a property "childprop" of
1094 * childnode (in this case, a string)
1095 */
1096 };
1097 };
1099 Nodes can contain other nodes etc... thus defining the hierarchical
1100 structure of the tree.
1102 Strings support common escape sequences from C: "\n", "\t", "\r",
1103 "\(octal value)", "\x(hex value)".
1105 It is also suggested that you pipe your source file through cpp (gcc
1106 preprocessor) so you can use #include's, #define for constants, etc...
1108 Finally, various options are planned but not yet implemented, like
1109 automatic generation of phandles, labels (exported to the asm file so
1110 you can point to a property content and change it easily from whatever
1111 you link the device-tree with), label or path instead of numeric value
1112 in some cells to "point" to a node (replaced by a phandle at compile
1113 time), export of reserve map address to the asm file, ability to
1114 specify reserve map content at compile time, etc...
1116 We may provide a .h include file with common definitions of that
1117 proves useful for some properties (like building PCI properties or
1118 interrupt maps) though it may be better to add a notion of struct
1119 definitions to the compiler...
1122 V - Recommendations for a bootloader
1123 ====================================
1126 Here are some various ideas/recommendations that have been proposed
1127 while all this has been defined and implemented.
1129 - The bootloader may want to be able to use the device-tree itself
1130 and may want to manipulate it (to add/edit some properties,
1131 like physical memory size or kernel arguments). At this point, 2
1132 choices can be made. Either the bootloader works directly on the
1133 flattened format, or the bootloader has its own internal tree
1134 representation with pointers (similar to the kernel one) and
1135 re-flattens the tree when booting the kernel. The former is a bit
1136 more difficult to edit/modify, the later requires probably a bit
1137 more code to handle the tree structure. Note that the structure
1138 format has been designed so it's relatively easy to "insert"
1139 properties or nodes or delete them by just memmoving things
1140 around. It contains no internal offsets or pointers for this
1141 purpose.
1143 - An example of code for iterating nodes & retrieving properties
1144 directly from the flattened tree format can be found in the kernel
1145 file arch/ppc64/kernel/prom.c, look at scan_flat_dt() function,
1146 its usage in early_init_devtree(), and the corresponding various
1147 early_init_dt_scan_*() callbacks. That code can be re-used in a
1148 GPL bootloader, and as the author of that code, I would be happy
1149 to discuss possible free licensing to any vendor who wishes to
1150 integrate all or part of this code into a non-GPL bootloader.
1154 VI - System-on-a-chip devices and nodes
1155 =======================================
1157 Many companies are now starting to develop system-on-a-chip
1158 processors, where the processor core (CPU) and many peripheral devices
1159 exist on a single piece of silicon. For these SOCs, an SOC node
1160 should be used that defines child nodes for the devices that make
1161 up the SOC. While platforms are not required to use this model in
1162 order to boot the kernel, it is highly encouraged that all SOC
1163 implementations define as complete a flat-device-tree as possible to
1164 describe the devices on the SOC. This will allow for the
1165 genericization of much of the kernel code.
1168 1) Defining child nodes of an SOC
1169 ---------------------------------
1171 Each device that is part of an SOC may have its own node entry inside
1172 the SOC node. For each device that is included in the SOC, the unit
1173 address property represents the address offset for this device's
1174 memory-mapped registers in the parent's address space. The parent's
1175 address space is defined by the "ranges" property in the top-level soc
1176 node. The "reg" property for each node that exists directly under the
1177 SOC node should contain the address mapping from the child address space
1178 to the parent SOC address space and the size of the device's
1179 memory-mapped register file.
1181 For many devices that may exist inside an SOC, there are predefined
1182 specifications for the format of the device tree node. All SOC child
1183 nodes should follow these specifications, except where noted in this
1184 document.
1186 See appendix A for an example partial SOC node definition for the
1187 MPC8540.
1190 2) Representing devices without a current OF specification
1191 ----------------------------------------------------------
1193 Currently, there are many devices on SOCs that do not have a standard
1194 representation pre-defined as part of the open firmware
1195 specifications, mainly because the boards that contain these SOCs are
1196 not currently booted using open firmware. This section contains
1197 descriptions for the SOC devices for which new nodes have been
1198 defined; this list will expand as more and more SOC-containing
1199 platforms are moved over to use the flattened-device-tree model.
1201 a) MDIO IO device
1203 The MDIO is a bus to which the PHY devices are connected. For each
1204 device that exists on this bus, a child node should be created. See
1205 the definition of the PHY node below for an example of how to define
1206 a PHY.
1208 Required properties:
1209 - reg : Offset and length of the register set for the device
1210 - device_type : Should be "mdio"
1211 - compatible : Should define the compatible device type for the
1212 mdio. Currently, this is most likely to be "gianfar"
1214 Example:
1216 mdio@24520 {
1217 reg = <24520 20>;
1218 device_type = "mdio";
1219 compatible = "gianfar";
1221 ethernet-phy@0 {
1222 ......
1223 };
1224 };
1227 b) Gianfar-compatible ethernet nodes
1229 Required properties:
1231 - device_type : Should be "network"
1232 - model : Model of the device. Can be "TSEC", "eTSEC", or "FEC"
1233 - compatible : Should be "gianfar"
1234 - reg : Offset and length of the register set for the device
1235 - mac-address : List of bytes representing the ethernet address of
1236 this controller
1237 - interrupts : <a b> where a is the interrupt number and b is a
1238 field that represents an encoding of the sense and level
1239 information for the interrupt. This should be encoded based on
1240 the information in section 2) depending on the type of interrupt
1241 controller you have.
1242 - interrupt-parent : the phandle for the interrupt controller that
1243 services interrupts for this device.
1244 - phy-handle : The phandle for the PHY connected to this ethernet
1245 controller.
1247 Recommended properties:
1249 - linux,network-index : This is the intended "index" of this
1250 network device. This is used by the bootwrapper to interpret
1251 MAC addresses passed by the firmware when no information other
1252 than indices is available to associate an address with a device.
1253 - phy-connection-type : a string naming the controller/PHY interface type,
1254 i.e., "mii" (default), "rmii", "gmii", "rgmii", "rgmii-id", "sgmii",
1255 "tbi", or "rtbi". This property is only really needed if the connection
1256 is of type "rgmii-id", as all other connection types are detected by
1257 hardware.
1260 Example:
1262 ethernet@24000 {
1263 #size-cells = <0>;
1264 device_type = "network";
1265 model = "TSEC";
1266 compatible = "gianfar";
1267 reg = <24000 1000>;
1268 mac-address = [ 00 E0 0C 00 73 00 ];
1269 interrupts = <d 3 e 3 12 3>;
1270 interrupt-parent = <40000>;
1271 phy-handle = <2452000>
1272 };
1276 c) PHY nodes
1278 Required properties:
1280 - device_type : Should be "ethernet-phy"
1281 - interrupts : <a b> where a is the interrupt number and b is a
1282 field that represents an encoding of the sense and level
1283 information for the interrupt. This should be encoded based on
1284 the information in section 2) depending on the type of interrupt
1285 controller you have.
1286 - interrupt-parent : the phandle for the interrupt controller that
1287 services interrupts for this device.
1288 - reg : The ID number for the phy, usually a small integer
1289 - linux,phandle : phandle for this node; likely referenced by an
1290 ethernet controller node.
1293 Example:
1295 ethernet-phy@0 {
1296 linux,phandle = <2452000>
1297 interrupt-parent = <40000>;
1298 interrupts = <35 1>;
1299 reg = <0>;
1300 device_type = "ethernet-phy";
1301 };
1304 d) Interrupt controllers
1306 Some SOC devices contain interrupt controllers that are different
1307 from the standard Open PIC specification. The SOC device nodes for
1308 these types of controllers should be specified just like a standard
1309 OpenPIC controller. Sense and level information should be encoded
1310 as specified in section 2) of this chapter for each device that
1311 specifies an interrupt.
1313 Example :
1315 pic@40000 {
1316 linux,phandle = <40000>;
1317 clock-frequency = <0>;
1318 interrupt-controller;
1319 #address-cells = <0>;
1320 reg = <40000 40000>;
1321 built-in;
1322 compatible = "chrp,open-pic";
1323 device_type = "open-pic";
1324 big-endian;
1325 };
1328 e) I2C
1330 Required properties :
1332 - device_type : Should be "i2c"
1333 - reg : Offset and length of the register set for the device
1335 Recommended properties :
1337 - compatible : Should be "fsl-i2c" for parts compatible with
1338 Freescale I2C specifications.
1339 - interrupts : <a b> where a is the interrupt number and b is a
1340 field that represents an encoding of the sense and level
1341 information for the interrupt. This should be encoded based on
1342 the information in section 2) depending on the type of interrupt
1343 controller you have.
1344 - interrupt-parent : the phandle for the interrupt controller that
1345 services interrupts for this device.
1346 - dfsrr : boolean; if defined, indicates that this I2C device has
1347 a digital filter sampling rate register
1348 - fsl5200-clocking : boolean; if defined, indicated that this device
1349 uses the FSL 5200 clocking mechanism.
1351 Example :
1353 i2c@3000 {
1354 interrupt-parent = <40000>;
1355 interrupts = <1b 3>;
1356 reg = <3000 18>;
1357 device_type = "i2c";
1358 compatible = "fsl-i2c";
1359 dfsrr;
1360 };
1363 f) Freescale SOC USB controllers
1365 The device node for a USB controller that is part of a Freescale
1366 SOC is as described in the document "Open Firmware Recommended
1367 Practice : Universal Serial Bus" with the following modifications
1368 and additions :
1370 Required properties :
1371 - compatible : Should be "fsl-usb2-mph" for multi port host USB
1372 controllers, or "fsl-usb2-dr" for dual role USB controllers
1373 - phy_type : For multi port host USB controllers, should be one of
1374 "ulpi", or "serial". For dual role USB controllers, should be
1375 one of "ulpi", "utmi", "utmi_wide", or "serial".
1376 - reg : Offset and length of the register set for the device
1377 - port0 : boolean; if defined, indicates port0 is connected for
1378 fsl-usb2-mph compatible controllers. Either this property or
1379 "port1" (or both) must be defined for "fsl-usb2-mph" compatible
1380 controllers.
1381 - port1 : boolean; if defined, indicates port1 is connected for
1382 fsl-usb2-mph compatible controllers. Either this property or
1383 "port0" (or both) must be defined for "fsl-usb2-mph" compatible
1384 controllers.
1385 - dr_mode : indicates the working mode for "fsl-usb2-dr" compatible
1386 controllers. Can be "host", "peripheral", or "otg". Default to
1387 "host" if not defined for backward compatibility.
1389 Recommended properties :
1390 - interrupts : <a b> where a is the interrupt number and b is a
1391 field that represents an encoding of the sense and level
1392 information for the interrupt. This should be encoded based on
1393 the information in section 2) depending on the type of interrupt
1394 controller you have.
1395 - interrupt-parent : the phandle for the interrupt controller that
1396 services interrupts for this device.
1398 Example multi port host USB controller device node :
1399 usb@22000 {
1400 device_type = "usb";
1401 compatible = "fsl-usb2-mph";
1402 reg = <22000 1000>;
1403 #address-cells = <1>;
1404 #size-cells = <0>;
1405 interrupt-parent = <700>;
1406 interrupts = <27 1>;
1407 phy_type = "ulpi";
1408 port0;
1409 port1;
1410 };
1412 Example dual role USB controller device node :
1413 usb@23000 {
1414 device_type = "usb";
1415 compatible = "fsl-usb2-dr";
1416 reg = <23000 1000>;
1417 #address-cells = <1>;
1418 #size-cells = <0>;
1419 interrupt-parent = <700>;
1420 interrupts = <26 1>;
1421 dr_mode = "otg";
1422 phy = "ulpi";
1423 };
1426 g) Freescale SOC SEC Security Engines
1428 Required properties:
1430 - device_type : Should be "crypto"
1431 - model : Model of the device. Should be "SEC1" or "SEC2"
1432 - compatible : Should be "talitos"
1433 - reg : Offset and length of the register set for the device
1434 - interrupts : <a b> where a is the interrupt number and b is a
1435 field that represents an encoding of the sense and level
1436 information for the interrupt. This should be encoded based on
1437 the information in section 2) depending on the type of interrupt
1438 controller you have.
1439 - interrupt-parent : the phandle for the interrupt controller that
1440 services interrupts for this device.
1441 - num-channels : An integer representing the number of channels
1442 available.
1443 - channel-fifo-len : An integer representing the number of
1444 descriptor pointers each channel fetch fifo can hold.
1445 - exec-units-mask : The bitmask representing what execution units
1446 (EUs) are available. It's a single 32-bit cell. EU information
1447 should be encoded following the SEC's Descriptor Header Dword
1448 EU_SEL0 field documentation, i.e. as follows:
1450 bit 0 = reserved - should be 0
1451 bit 1 = set if SEC has the ARC4 EU (AFEU)
1452 bit 2 = set if SEC has the DES/3DES EU (DEU)
1453 bit 3 = set if SEC has the message digest EU (MDEU)
1454 bit 4 = set if SEC has the random number generator EU (RNG)
1455 bit 5 = set if SEC has the public key EU (PKEU)
1456 bit 6 = set if SEC has the AES EU (AESU)
1457 bit 7 = set if SEC has the Kasumi EU (KEU)
1459 bits 8 through 31 are reserved for future SEC EUs.
1461 - descriptor-types-mask : The bitmask representing what descriptors
1462 are available. It's a single 32-bit cell. Descriptor type
1463 information should be encoded following the SEC's Descriptor
1464 Header Dword DESC_TYPE field documentation, i.e. as follows:
1466 bit 0 = set if SEC supports the aesu_ctr_nonsnoop desc. type
1467 bit 1 = set if SEC supports the ipsec_esp descriptor type
1468 bit 2 = set if SEC supports the common_nonsnoop desc. type
1469 bit 3 = set if SEC supports the 802.11i AES ccmp desc. type
1470 bit 4 = set if SEC supports the hmac_snoop_no_afeu desc. type
1471 bit 5 = set if SEC supports the srtp descriptor type
1472 bit 6 = set if SEC supports the non_hmac_snoop_no_afeu desc.type
1473 bit 7 = set if SEC supports the pkeu_assemble descriptor type
1474 bit 8 = set if SEC supports the aesu_key_expand_output desc.type
1475 bit 9 = set if SEC supports the pkeu_ptmul descriptor type
1476 bit 10 = set if SEC supports the common_nonsnoop_afeu desc. type
1477 bit 11 = set if SEC supports the pkeu_ptadd_dbl descriptor type
1479 ..and so on and so forth.
1481 Example:
1483 /* MPC8548E */
1484 crypto@30000 {
1485 device_type = "crypto";
1486 model = "SEC2";
1487 compatible = "talitos";
1488 reg = <30000 10000>;
1489 interrupts = <1d 3>;
1490 interrupt-parent = <40000>;
1491 num-channels = <4>;
1492 channel-fifo-len = <18>;
1493 exec-units-mask = <000000fe>;
1494 descriptor-types-mask = <012b0ebf>;
1495 };
1497 h) Board Control and Status (BCSR)
1499 Required properties:
1501 - device_type : Should be "board-control"
1502 - reg : Offset and length of the register set for the device
1504 Example:
1506 bcsr@f8000000 {
1507 device_type = "board-control";
1508 reg = <f8000000 8000>;
1509 };
1511 i) Freescale QUICC Engine module (QE)
1512 This represents qe module that is installed on PowerQUICC II Pro.
1513 Hopefully it will merge backward compatibility with CPM/CPM2.
1514 Basically, it is a bus of devices, that could act more or less
1515 as a complete entity (UCC, USB etc ). All of them should be siblings on
1516 the "root" qe node, using the common properties from there.
1517 The description below applies to the qe of MPC8360 and
1518 more nodes and properties would be extended in the future.
1520 i) Root QE device
1522 Required properties:
1523 - device_type : should be "qe";
1524 - model : precise model of the QE, Can be "QE", "CPM", or "CPM2"
1525 - reg : offset and length of the device registers.
1526 - bus-frequency : the clock frequency for QUICC Engine.
1528 Recommended properties
1529 - brg-frequency : the internal clock source frequency for baud-rate
1530 generators in Hz.
1532 Example:
1533 qe@e0100000 {
1534 #address-cells = <1>;
1535 #size-cells = <1>;
1536 #interrupt-cells = <2>;
1537 device_type = "qe";
1538 model = "QE";
1539 ranges = <0 e0100000 00100000>;
1540 reg = <e0100000 480>;
1541 brg-frequency = <0>;
1542 bus-frequency = <179A7B00>;
1543 }
1546 ii) SPI (Serial Peripheral Interface)
1548 Required properties:
1549 - device_type : should be "spi".
1550 - compatible : should be "fsl_spi".
1551 - mode : the SPI operation mode, it can be "cpu" or "qe".
1552 - reg : Offset and length of the register set for the device
1553 - interrupts : <a b> where a is the interrupt number and b is a
1554 field that represents an encoding of the sense and level
1555 information for the interrupt. This should be encoded based on
1556 the information in section 2) depending on the type of interrupt
1557 controller you have.
1558 - interrupt-parent : the phandle for the interrupt controller that
1559 services interrupts for this device.
1561 Example:
1562 spi@4c0 {
1563 device_type = "spi";
1564 compatible = "fsl_spi";
1565 reg = <4c0 40>;
1566 interrupts = <82 0>;
1567 interrupt-parent = <700>;
1568 mode = "cpu";
1569 };
1572 iii) USB (Universal Serial Bus Controller)
1574 Required properties:
1575 - device_type : should be "usb".
1576 - compatible : could be "qe_udc" or "fhci-hcd".
1577 - mode : the could be "host" or "slave".
1578 - reg : Offset and length of the register set for the device
1579 - interrupts : <a b> where a is the interrupt number and b is a
1580 field that represents an encoding of the sense and level
1581 information for the interrupt. This should be encoded based on
1582 the information in section 2) depending on the type of interrupt
1583 controller you have.
1584 - interrupt-parent : the phandle for the interrupt controller that
1585 services interrupts for this device.
1587 Example(slave):
1588 usb@6c0 {
1589 device_type = "usb";
1590 compatible = "qe_udc";
1591 reg = <6c0 40>;
1592 interrupts = <8b 0>;
1593 interrupt-parent = <700>;
1594 mode = "slave";
1595 };
1598 iv) UCC (Unified Communications Controllers)
1600 Required properties:
1601 - device_type : should be "network", "hldc", "uart", "transparent"
1602 "bisync" or "atm".
1603 - compatible : could be "ucc_geth" or "fsl_atm" and so on.
1604 - model : should be "UCC".
1605 - device-id : the ucc number(1-8), corresponding to UCCx in UM.
1606 - reg : Offset and length of the register set for the device
1607 - interrupts : <a b> where a is the interrupt number and b is a
1608 field that represents an encoding of the sense and level
1609 information for the interrupt. This should be encoded based on
1610 the information in section 2) depending on the type of interrupt
1611 controller you have.
1612 - interrupt-parent : the phandle for the interrupt controller that
1613 services interrupts for this device.
1614 - pio-handle : The phandle for the Parallel I/O port configuration.
1615 - rx-clock : represents the UCC receive clock source.
1616 0x00 : clock source is disabled;
1617 0x1~0x10 : clock source is BRG1~BRG16 respectively;
1618 0x11~0x28: clock source is QE_CLK1~QE_CLK24 respectively.
1619 - tx-clock: represents the UCC transmit clock source;
1620 0x00 : clock source is disabled;
1621 0x1~0x10 : clock source is BRG1~BRG16 respectively;
1622 0x11~0x28: clock source is QE_CLK1~QE_CLK24 respectively.
1624 Required properties for network device_type:
1625 - mac-address : list of bytes representing the ethernet address.
1626 - phy-handle : The phandle for the PHY connected to this controller.
1628 Recommended properties:
1629 - linux,network-index : This is the intended "index" of this
1630 network device. This is used by the bootwrapper to interpret
1631 MAC addresses passed by the firmware when no information other
1632 than indices is available to associate an address with a device.
1633 - phy-connection-type : a string naming the controller/PHY interface type,
1634 i.e., "mii" (default), "rmii", "gmii", "rgmii", "rgmii-id", "tbi",
1635 or "rtbi".
1637 Example:
1638 ucc@2000 {
1639 device_type = "network";
1640 compatible = "ucc_geth";
1641 model = "UCC";
1642 device-id = <1>;
1643 reg = <2000 200>;
1644 interrupts = <a0 0>;
1645 interrupt-parent = <700>;
1646 mac-address = [ 00 04 9f 00 23 23 ];
1647 rx-clock = "none";
1648 tx-clock = "clk9";
1649 phy-handle = <212000>;
1650 phy-connection-type = "gmii";
1651 pio-handle = <140001>;
1652 };
1655 v) Parallel I/O Ports
1657 This node configures Parallel I/O ports for CPUs with QE support.
1658 The node should reside in the "soc" node of the tree. For each
1659 device that using parallel I/O ports, a child node should be created.
1660 See the definition of the Pin configuration nodes below for more
1661 information.
1663 Required properties:
1664 - device_type : should be "par_io".
1665 - reg : offset to the register set and its length.
1666 - num-ports : number of Parallel I/O ports
1668 Example:
1669 par_io@1400 {
1670 reg = <1400 100>;
1671 #address-cells = <1>;
1672 #size-cells = <0>;
1673 device_type = "par_io";
1674 num-ports = <7>;
1675 ucc_pin@01 {
1676 ......
1677 };
1680 vi) Pin configuration nodes
1682 Required properties:
1683 - linux,phandle : phandle of this node; likely referenced by a QE
1684 device.
1685 - pio-map : array of pin configurations. Each pin is defined by 6
1686 integers. The six numbers are respectively: port, pin, dir,
1687 open_drain, assignment, has_irq.
1688 - port : port number of the pin; 0-6 represent port A-G in UM.
1689 - pin : pin number in the port.
1690 - dir : direction of the pin, should encode as follows:
1692 0 = The pin is disabled
1693 1 = The pin is an output
1694 2 = The pin is an input
1695 3 = The pin is I/O
1697 - open_drain : indicates the pin is normal or wired-OR:
1699 0 = The pin is actively driven as an output
1700 1 = The pin is an open-drain driver. As an output, the pin is
1701 driven active-low, otherwise it is three-stated.
1703 - assignment : function number of the pin according to the Pin Assignment
1704 tables in User Manual. Each pin can have up to 4 possible functions in
1705 QE and two options for CPM.
1706 - has_irq : indicates if the pin is used as source of external
1707 interrupts.
1709 Example:
1710 ucc_pin@01 {
1711 linux,phandle = <140001>;
1712 pio-map = <
1713 /* port pin dir open_drain assignment has_irq */
1714 0 3 1 0 1 0 /* TxD0 */
1715 0 4 1 0 1 0 /* TxD1 */
1716 0 5 1 0 1 0 /* TxD2 */
1717 0 6 1 0 1 0 /* TxD3 */
1718 1 6 1 0 3 0 /* TxD4 */
1719 1 7 1 0 1 0 /* TxD5 */
1720 1 9 1 0 2 0 /* TxD6 */
1721 1 a 1 0 2 0 /* TxD7 */
1722 0 9 2 0 1 0 /* RxD0 */
1723 0 a 2 0 1 0 /* RxD1 */
1724 0 b 2 0 1 0 /* RxD2 */
1725 0 c 2 0 1 0 /* RxD3 */
1726 0 d 2 0 1 0 /* RxD4 */
1727 1 1 2 0 2 0 /* RxD5 */
1728 1 0 2 0 2 0 /* RxD6 */
1729 1 4 2 0 2 0 /* RxD7 */
1730 0 7 1 0 1 0 /* TX_EN */
1731 0 8 1 0 1 0 /* TX_ER */
1732 0 f 2 0 1 0 /* RX_DV */
1733 0 10 2 0 1 0 /* RX_ER */
1734 0 0 2 0 1 0 /* RX_CLK */
1735 2 9 1 0 3 0 /* GTX_CLK - CLK10 */
1736 2 8 2 0 1 0>; /* GTX125 - CLK9 */
1737 };
1739 vii) Multi-User RAM (MURAM)
1741 Required properties:
1742 - device_type : should be "muram".
1743 - mode : the could be "host" or "slave".
1744 - ranges : Should be defined as specified in 1) to describe the
1745 translation of MURAM addresses.
1746 - data-only : sub-node which defines the address area under MURAM
1747 bus that can be allocated as data/parameter
1749 Example:
1751 muram@10000 {
1752 device_type = "muram";
1753 ranges = <0 00010000 0000c000>;
1755 data-only@0{
1756 reg = <0 c000>;
1757 };
1758 };
1760 j) Flash chip nodes
1762 Flash chips (Memory Technology Devices) are often used for solid state
1763 file systems on embedded devices.
1765 Required properties:
1767 - device_type : has to be "rom"
1768 - compatible : Should specify what this flash device is compatible with.
1769 Currently, this is most likely to be "direct-mapped" (which
1770 corresponds to the MTD physmap mapping driver).
1771 - reg : Offset and length of the register set (or memory mapping) for
1772 the device.
1773 - bank-width : Width of the flash data bus in bytes. Required
1774 for the NOR flashes (compatible == "direct-mapped" and others) ONLY.
1776 Recommended properties :
1778 - partitions : Several pairs of 32-bit values where the first value is
1779 partition's offset from the start of the device and the second one is
1780 partition size in bytes with LSB used to signify a read only
1781 partition (so, the partition size should always be an even number).
1782 - partition-names : The list of concatenated zero terminated strings
1783 representing the partition names.
1784 - probe-type : The type of probe which should be done for the chip
1785 (JEDEC vs CFI actually). Valid ONLY for NOR flashes.
1787 Example:
1789 flash@ff000000 {
1790 device_type = "rom";
1791 compatible = "direct-mapped";
1792 probe-type = "CFI";
1793 reg = <ff000000 01000000>;
1794 bank-width = <4>;
1795 partitions = <00000000 00f80000
1796 00f80000 00080001>;
1797 partition-names = "fs\0firmware";
1798 };
1800 k) Global Utilities Block
1802 The global utilities block controls power management, I/O device
1803 enabling, power-on-reset configuration monitoring, general-purpose
1804 I/O signal configuration, alternate function selection for multiplexed
1805 signals, and clock control.
1807 Required properties:
1809 - compatible : Should define the compatible device type for
1810 global-utilities.
1811 - reg : Offset and length of the register set for the device.
1813 Recommended properties:
1815 - fsl,has-rstcr : Indicates that the global utilities register set
1816 contains a functioning "reset control register" (i.e. the board
1817 is wired to reset upon setting the HRESET_REQ bit in this register).
1819 Example:
1821 global-utilities@e0000 { /* global utilities block */
1822 compatible = "fsl,mpc8548-guts";
1823 reg = <e0000 1000>;
1824 fsl,has-rstcr;
1825 };
1827 More devices will be defined as this spec matures.
1829 VII - Specifying interrupt information for devices
1830 ===================================================
1832 The device tree represents the busses and devices of a hardware
1833 system in a form similar to the physical bus topology of the
1834 hardware.
1836 In addition, a logical 'interrupt tree' exists which represents the
1837 hierarchy and routing of interrupts in the hardware.
1839 The interrupt tree model is fully described in the
1840 document "Open Firmware Recommended Practice: Interrupt
1841 Mapping Version 0.9". The document is available at:
1842 <http://playground.sun.com/1275/practice>.
1844 1) interrupts property
1845 ----------------------
1847 Devices that generate interrupts to a single interrupt controller
1848 should use the conventional OF representation described in the
1849 OF interrupt mapping documentation.
1851 Each device which generates interrupts must have an 'interrupt'
1852 property. The interrupt property value is an arbitrary number of
1853 of 'interrupt specifier' values which describe the interrupt or
1854 interrupts for the device.
1856 The encoding of an interrupt specifier is determined by the
1857 interrupt domain in which the device is located in the
1858 interrupt tree. The root of an interrupt domain specifies in
1859 its #interrupt-cells property the number of 32-bit cells
1860 required to encode an interrupt specifier. See the OF interrupt
1861 mapping documentation for a detailed description of domains.
1863 For example, the binding for the OpenPIC interrupt controller
1864 specifies an #interrupt-cells value of 2 to encode the interrupt
1865 number and level/sense information. All interrupt children in an
1866 OpenPIC interrupt domain use 2 cells per interrupt in their interrupts
1867 property.
1869 The PCI bus binding specifies a #interrupt-cell value of 1 to encode
1870 which interrupt pin (INTA,INTB,INTC,INTD) is used.
1872 2) interrupt-parent property
1873 ----------------------------
1875 The interrupt-parent property is specified to define an explicit
1876 link between a device node and its interrupt parent in
1877 the interrupt tree. The value of interrupt-parent is the
1878 phandle of the parent node.
1880 If the interrupt-parent property is not defined for a node, it's
1881 interrupt parent is assumed to be an ancestor in the node's
1882 _device tree_ hierarchy.
1884 3) OpenPIC Interrupt Controllers
1885 --------------------------------
1887 OpenPIC interrupt controllers require 2 cells to encode
1888 interrupt information. The first cell defines the interrupt
1889 number. The second cell defines the sense and level
1890 information.
1892 Sense and level information should be encoded as follows:
1894 0 = low to high edge sensitive type enabled
1895 1 = active low level sensitive type enabled
1896 2 = active high level sensitive type enabled
1897 3 = high to low edge sensitive type enabled
1899 4) ISA Interrupt Controllers
1900 ----------------------------
1902 ISA PIC interrupt controllers require 2 cells to encode
1903 interrupt information. The first cell defines the interrupt
1904 number. The second cell defines the sense and level
1905 information.
1907 ISA PIC interrupt controllers should adhere to the ISA PIC
1908 encodings listed below:
1910 0 = active low level sensitive type enabled
1911 1 = active high level sensitive type enabled
1912 2 = high to low edge sensitive type enabled
1913 3 = low to high edge sensitive type enabled
1916 Appendix A - Sample SOC node for MPC8540
1917 ========================================
1919 Note that the #address-cells and #size-cells for the SoC node
1920 in this example have been explicitly listed; these are likely
1921 not necessary as they are usually the same as the root node.
1923 soc8540@e0000000 {
1924 #address-cells = <1>;
1925 #size-cells = <1>;
1926 #interrupt-cells = <2>;
1927 device_type = "soc";
1928 ranges = <00000000 e0000000 00100000>
1929 reg = <e0000000 00003000>;
1930 bus-frequency = <0>;
1932 mdio@24520 {
1933 reg = <24520 20>;
1934 device_type = "mdio";
1935 compatible = "gianfar";
1937 ethernet-phy@0 {
1938 linux,phandle = <2452000>
1939 interrupt-parent = <40000>;
1940 interrupts = <35 1>;
1941 reg = <0>;
1942 device_type = "ethernet-phy";
1943 };
1945 ethernet-phy@1 {
1946 linux,phandle = <2452001>
1947 interrupt-parent = <40000>;
1948 interrupts = <35 1>;
1949 reg = <1>;
1950 device_type = "ethernet-phy";
1951 };
1953 ethernet-phy@3 {
1954 linux,phandle = <2452002>
1955 interrupt-parent = <40000>;
1956 interrupts = <35 1>;
1957 reg = <3>;
1958 device_type = "ethernet-phy";
1959 };
1961 };
1963 ethernet@24000 {
1964 #size-cells = <0>;
1965 device_type = "network";
1966 model = "TSEC";
1967 compatible = "gianfar";
1968 reg = <24000 1000>;
1969 mac-address = [ 00 E0 0C 00 73 00 ];
1970 interrupts = <d 3 e 3 12 3>;
1971 interrupt-parent = <40000>;
1972 phy-handle = <2452000>;
1973 };
1975 ethernet@25000 {
1976 #address-cells = <1>;
1977 #size-cells = <0>;
1978 device_type = "network";
1979 model = "TSEC";
1980 compatible = "gianfar";
1981 reg = <25000 1000>;
1982 mac-address = [ 00 E0 0C 00 73 01 ];
1983 interrupts = <13 3 14 3 18 3>;
1984 interrupt-parent = <40000>;
1985 phy-handle = <2452001>;
1986 };
1988 ethernet@26000 {
1989 #address-cells = <1>;
1990 #size-cells = <0>;
1991 device_type = "network";
1992 model = "FEC";
1993 compatible = "gianfar";
1994 reg = <26000 1000>;
1995 mac-address = [ 00 E0 0C 00 73 02 ];
1996 interrupts = <19 3>;
1997 interrupt-parent = <40000>;
1998 phy-handle = <2452002>;
1999 };
2001 serial@4500 {
2002 device_type = "serial";
2003 compatible = "ns16550";
2004 reg = <4500 100>;
2005 clock-frequency = <0>;
2006 interrupts = <1a 3>;
2007 interrupt-parent = <40000>;
2008 };
2010 pic@40000 {
2011 linux,phandle = <40000>;
2012 clock-frequency = <0>;
2013 interrupt-controller;
2014 #address-cells = <0>;
2015 reg = <40000 40000>;
2016 built-in;
2017 compatible = "chrp,open-pic";
2018 device_type = "open-pic";
2019 big-endian;
2020 };
2022 i2c@3000 {
2023 interrupt-parent = <40000>;
2024 interrupts = <1b 3>;
2025 reg = <3000 18>;
2026 device_type = "i2c";
2027 compatible = "fsl-i2c";
2028 dfsrr;
2029 };
2031 };