--- /dev/null
+ 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
+
+ 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 alignement between property size
+ and property data. The old style variable
+ alignment would make it impossible to do
+ "simple" insertion of properties using
+ memove (thanks Milton for
+ noticing). Updated kernel patch as well
+ - Correct a few more alignement 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 differenciate 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 include/asm-powerpc/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 architectire. 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
+ roughtly described in include/asm-powerpc/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 */
+};
+
+ 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. You should always generate a structure of the highest
+ version defined at the time of your implementation. Currently
+ that is version 16, unless you explicitely 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 0x10 if you generate a tree of version 0x10
+ 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)
+
+
+ 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 0x10 makes it
+optional as it can generate it from the unit name defined below.
+
+There is also a "unit name" that is used to differenciate nodes with
+the same name at the same level, it is usually made of the node
+name's, 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>
+ | |- linux,boot-cpu
+ | |- 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,platform = <00000600>
+ |- 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/linux,boot-cpu 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 of 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 summmarised as a start token, a full path,
+a list of properties, a list of child node and an end token. Every
+child node is a full node structure itself as defined above.
+
+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 flatenned 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 chose 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
+property. In the absence of such a property, the parent's parent
+values are used, etc... 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. The format of the "ranges" proprety 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.
+
+
+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 flexibe 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
+
+ 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 (see /chosen/linux,platform for how the kernel choses a
+ platform type) 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-line-size : one cell, L1 data cache line size in bytes
+ - i-cache-line-size : one cell, L1 instruction cache line 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
+ - linux, boot-cpu : Should be defined if this cpu is the boot cpu.
+
+ 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.
+
+ 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 beeing 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
+ phandle pointers to nodes like the main interrupt controller, 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.
+
+ Required properties:
+
+ - linux,platform : This is your platform number as assigned by the
+ architecture maintainers
+
+ 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 it's own default console. If you look at the funciton
+ 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.
+ - interrupt-controller : This is one cell containing a phandle
+ value that matches the "linux,phandle" property of your main
+ interrupt controller node. May be used for interrupt routing.
+
+
+ Note that u-boot creates and fills in the chosen node for platforms
+ that use it.
+
+ 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.
+
+ 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 an
+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>;
+ }
+
+
+
+IV - "dtc", the device tree compiler
+====================================
+
+
+dtc source code can be found at
+<http://ozlabs.org/~dgibson/dtc/dtc.tar.gz>
+
+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 use
+
+
+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 versio 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 commments.
+
+/ {
+}
+
+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 bits value (hexadecimal)
+ */
+
+ property3 = <12345678 12345678 deadbeef>;
+ /* define a property containing 3
+ * numerical 32 bits 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 & retreiving 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,
+ it's 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
+ do discuss possible free licencing 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) Specifying interrupt information for SOC devices
+---------------------------------------------------
+
+Each device that is part of an SOC and which generates interrupts
+should have the following properties:
+
+ - interrupt-parent : contains the phandle of the interrupt
+ controller which handles interrupts for this device
+ - interrupts : a list of tuples representing the interrupt
+ number and the interrupt sense and level for each interupt
+ for this device.
+
+This information is used by the kernel to build the interrupt table
+for the interrupt controllers in the system.
+
+Sense and level information should be encoded as follows:
+
+ Devices connected to openPIC-compatible controllers should encode
+ sense and polarity as follows:
+
+ 0 = high to low edge sensitive type enabled
+ 1 = active low level sensitive type enabled
+ 2 = low to high edge sensitive type enabled
+ 3 = active high level sensitive type enabled
+
+ 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
+
+
+
+3) 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.
+
+ a) MDIO IO device
+
+ The MDIO is a bus to which the PHY devices are connected. For each
+ device that exists on this bus, a child node should be created. See
+ the definition of the PHY node below for an example of how to define
+ a PHY.
+
+ Required properties:
+ - reg : Offset and length of the register set for the device
+ - device_type : Should be "mdio"
+ - compatible : Should define the compatible device type for the
+ mdio. Currently, this is most likely to be "gianfar"
+
+ Example:
+
+ mdio@24520 {
+ reg = <24520 20>;
+
+ ethernet-phy@0 {
+ ......
+ };
+ };
+
+
+ b) Gianfar-compatible ethernet nodes
+
+ Required properties:
+
+ - device_type : Should be "network"
+ - model : Model of the device. Can be "TSEC", "eTSEC", or "FEC"
+ - compatible : Should be "gianfar"
+ - reg : Offset and length of the register set for the device
+ - address : List of bytes representing the ethernet address of
+ this controller
+ - interrupts : <a b> where a is the interrupt number and b is a
+ field that represents an encoding of the sense and level
+ information for the interrupt. This should be encoded based on
+ the information in section 2) depending on the type of interrupt
+ controller you have.
+ - interrupt-parent : the phandle for the interrupt controller that
+ services interrupts for this device.
+ - phy-handle : The phandle for the PHY connected to this ethernet
+ controller.
+
+ Example:
+
+ ethernet@24000 {
+ #size-cells = <0>;
+ device_type = "network";
+ model = "TSEC";
+ compatible = "gianfar";
+ reg = <24000 1000>;
+ address = [ 00 E0 0C 00 73 00 ];
+ interrupts = <d 3 e 3 12 3>;
+ interrupt-parent = <40000>;
+ phy-handle = <2452000>
+ };
+
+
+
+ c) PHY nodes
+
+ Required properties:
+
+ - device_type : Should be "ethernet-phy"
+ - interrupts : <a b> where a is the interrupt number and b is a
+ field that represents an encoding of the sense and level
+ information for the interrupt. This should be encoded based on
+ the information in section 2) depending on the type of interrupt
+ controller you have.
+ - interrupt-parent : the phandle for the interrupt controller that
+ services interrupts for this device.
+ - reg : The ID number for the phy, usually a small integer
+ - linux,phandle : phandle for this node; likely referenced by an
+ ethernet controller node.
+
+
+ Example:
+
+ ethernet-phy@0 {
+ linux,phandle = <2452000>
+ interrupt-parent = <40000>;
+ interrupts = <35 1>;
+ reg = <0>;
+ device_type = "ethernet-phy";
+ };
+
+
+ d) Interrupt controllers
+
+ Some SOC devices contain interrupt controllers that are different
+ from the standard Open PIC specification. The SOC device nodes for
+ these types of controllers should be specified just like a standard
+ OpenPIC controller. Sense and level information should be encoded
+ as specified in section 2) of this chapter for each device that
+ specifies an interrupt.
+
+ Example :
+
+ pic@40000 {
+ linux,phandle = <40000>;
+ clock-frequency = <0>;
+ interrupt-controller;
+ #address-cells = <0>;
+ reg = <40000 40000>;
+ built-in;
+ compatible = "chrp,open-pic";
+ device_type = "open-pic";
+ big-endian;
+ };
+
+
+ e) I2C
+
+ Required properties :
+
+ - device_type : Should be "i2c"
+ - reg : Offset and length of the register set for the device
+
+ Recommended properties :
+
+ - compatible : Should be "fsl-i2c" for parts compatible with
+ Freescale I2C specifications.
+ - interrupts : <a b> where a is the interrupt number and b is a
+ field that represents an encoding of the sense and level
+ information for the interrupt. This should be encoded based on
+ the information in section 2) depending on the type of interrupt
+ controller you have.
+ - interrupt-parent : the phandle for the interrupt controller that
+ services interrupts for this device.
+ - dfsrr : boolean; if defined, indicates that this I2C device has
+ a digital filter sampling rate register
+ - fsl5200-clocking : boolean; if defined, indicated that this device
+ uses the FSL 5200 clocking mechanism.
+
+ Example :
+
+ i2c@3000 {
+ interrupt-parent = <40000>;
+ interrupts = <1b 3>;
+ reg = <3000 18>;
+ device_type = "i2c";
+ compatible = "fsl-i2c";
+ dfsrr;
+ };
+
+
+ More devices will be defined as this spec matures.
+
+
+Appendix A - Sample SOC node for MPC8540
+========================================
+
+Note that the #address-cells and #size-cells for the SoC node
+in this example have been explicitly listed; these are likely
+not necessary as they are usually the same as the root node.
+
+ soc8540@e0000000 {
+ #address-cells = <1>;
+ #size-cells = <1>;
+ #interrupt-cells = <2>;
+ device_type = "soc";
+ ranges = <00000000 e0000000 00100000>
+ reg = <e0000000 00003000>;
+
+ mdio@24520 {
+ reg = <24520 20>;
+ device_type = "mdio";
+ compatible = "gianfar";
+
+ ethernet-phy@0 {
+ linux,phandle = <2452000>
+ interrupt-parent = <40000>;
+ interrupts = <35 1>;
+ reg = <0>;
+ device_type = "ethernet-phy";
+ };
+
+ ethernet-phy@1 {
+ linux,phandle = <2452001>
+ interrupt-parent = <40000>;
+ interrupts = <35 1>;
+ reg = <1>;
+ device_type = "ethernet-phy";
+ };
+
+ ethernet-phy@3 {
+ linux,phandle = <2452002>
+ interrupt-parent = <40000>;
+ interrupts = <35 1>;
+ reg = <3>;
+ device_type = "ethernet-phy";
+ };
+
+ };
+
+ ethernet@24000 {
+ #size-cells = <0>;
+ device_type = "network";
+ model = "TSEC";
+ compatible = "gianfar";
+ reg = <24000 1000>;
+ address = [ 00 E0 0C 00 73 00 ];
+ interrupts = <d 3 e 3 12 3>;
+ interrupt-parent = <40000>;
+ phy-handle = <2452000>;
+ };
+
+ ethernet@25000 {
+ #address-cells = <1>;
+ #size-cells = <0>;
+ device_type = "network";
+ model = "TSEC";
+ compatible = "gianfar";
+ reg = <25000 1000>;
+ address = [ 00 E0 0C 00 73 01 ];
+ interrupts = <13 3 14 3 18 3>;
+ interrupt-parent = <40000>;
+ phy-handle = <2452001>;
+ };
+
+ ethernet@26000 {
+ #address-cells = <1>;
+ #size-cells = <0>;
+ device_type = "network";
+ model = "FEC";
+ compatible = "gianfar";
+ reg = <26000 1000>;
+ address = [ 00 E0 0C 00 73 02 ];
+ interrupts = <19 3>;
+ interrupt-parent = <40000>;
+ phy-handle = <2452002>;
+ };
+
+ serial@4500 {
+ device_type = "serial";
+ compatible = "ns16550";
+ reg = <4500 100>;
+ clock-frequency = <0>;
+ interrupts = <1a 3>;
+ interrupt-parent = <40000>;
+ };
+
+ pic@40000 {
+ linux,phandle = <40000>;
+ clock-frequency = <0>;
+ interrupt-controller;
+ #address-cells = <0>;
+ reg = <40000 40000>;
+ built-in;
+ compatible = "chrp,open-pic";
+ device_type = "open-pic";
+ big-endian;
+ };
+
+ i2c@3000 {
+ interrupt-parent = <40000>;
+ interrupts = <1b 3>;
+ reg = <3000 18>;
+ device_type = "i2c";
+ compatible = "fsl-i2c";
+ dfsrr;
+ };
+
+ };
projects / GitHub / LineageOS / android_kernel_motorola_exynos9610.git / commitdiff