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--- flatteneddevicetree [2010/03/17 12:56] – RafalJaworowski
+++ flatteneddevicetree [2022/06/27 16:24] (current) – Add a noted that you can dump the DTB by sysctl and pipe it into dtc to get dts out again ... BjoernZeeb
@@ Line 1: / Line 1: @@
 ====== Flattened Device Tree ======
-This page is dedicated to the project bringing the flattened device tree (FDT) technology to the %%FreeBSD%%. For details contact RafalJaworowski. Work on this project is kindly sponsored by [[http://www.freebsdfoundation.org/|the FreeBSD Foundation]].
+This page is dedicated to the project bringing the flattened device tree (FDT) technology to the %%FreeBSD%%. For details contact RafalJaworowski. Work on this project was kindly sponsored by [[http://www.freebsdfoundation.org/|the FreeBSD Foundation]].
 ====== Abstract ======
 The objective of this project is to provide %%FreeBSD%% with the ability to use flattened device trees for description of hardware resources of a computer
-system and their dependencies, in a platform-neutral and portable way. The primary consumer of this functionality are embedded systems (based on [[FreeBSD/arm|ARM]], AVR32, [[FreeBSD/mips|MIPS]], [[powerpc|PowerPC]]), but the mechanism can be used in all cases when hardware resources cannot be self-enumerated (as such could be seen as a future replacement for [[http://www.FreeBSD.org/cgi/man.cgi?query=device.hints&apropos=0&sektion=0&manpath=FreeBSD+8-current&format=html|device.hints]] used in the legacy PC world).
+system and their dependencies, in a platform-neutral and portable way. The primary consumer of this functionality are embedded systems (based on [[arm|ARM]], AVR32, [[FreeBSD/mips|MIPS]], [[powerpc|PowerPC]]), but the mechanism can be used in all cases when hardware resources cannot be self-enumerated (as such could be seen as a future replacement for [[http://www.FreeBSD.org/cgi/man.cgi?query=device.hints&apropos=0&sektion=0&manpath=FreeBSD+8-current&format=html|device.hints]] used in the legacy PC world).
-====== Problem description ======
+====== Repository ======
-In embedded world there is great variety of systems based on same silicon chips, but designed into custom boards and devices, where connections of
+The code has been committed to the %%FreeBSD%% SVN repository as of r210053, and all development is now supposed to happen in the SVN HEAD.
-individual components are different and there are no conventions or rules, even across members of the same family of products.  Furthermore, some buses and interconnects are not self-enumerable by definition (unlike PCI or USB), and there has to be some prior knowledge about how they are connected and what their unique identification is. Some of the examples of typical problems are the following:
+The obsolete, no longer maintained original project development P4 branch can be found [[http://p4db.freebsd.org/changeList.cgi?FSPC=//depot/projects/fdt/...|here]].
+====== Introduction ======
+In embedded world there is great variety of systems based on similar silicon chips, but designed into custom boards and devices, where connections of
+individual components are different and there are no conventions or rules, even across members of the same family of products, for the interconnectios layout and resources allocation. Furthermore, some buses and interconnects are not self-enumerable by definition (unlike PCI or USB), and there has to be some prior knowledge about how they are connected and what their unique identification is. Some of the examples of typical problems are the following:
   * memory layout (address offsets/sizes specification)
@@ Line 20: / Line 25: @@
   * GPIO/multi-purpose pin routing and assignment
-The concept of flattened device trees is an established and mature way of handling such problems and has been successfully used for Linux/powerpc. It
+The concept of a **flattened device tree** (FDT) is an established and mature way of handling such problems and has been successfully used for Linux/powerpc. It has also been adopted as a basis for Power.org's embedded platform reference specification (ePAPR).
-has also been adopted as a basis for Power.org's embedded platform reference specification (ePAPR).
 The idea is inherited from Open Firmware IEEE 1275 device-tree notion (part of the regular Open Firmware implementation), but it allows to use device tree mechanism on all systems (not based on OF). It boils down to the following:
@@ Line 31: / Line 35: @@
   * the kernel (driver) learns about hardware resources details and dependencies from this [externally supplied] blob, which eliminates the need for embedding any info about the underlying platform's hardware resources in the kernel
-====== Documentation ======
+====== Quick start instructions ======
-[[FlattenedDeviceTree/doc|Documentation, howto]]
+This section is meant as a convenient helper for people, who want to quickly check out the idea of using FDT approach. It shows only the statically embedded DTB approach, with SHEEVAPLUG kernel config as an example. For other options and more detailed descriptions please see relevant parts of this manual.
-====== Repository ======
+===== Build FDT-enabled world =====
-The official project [[http://p4db.freebsd.org/changeList.cgi?FSPC=//depot/projects/fdt/...|branch]] in P4.
-====== Work break down ======
+<code>
+$ cd ${SRC}
+$ make -j 8 buildworld TARGET_ARCH=arm -DWITH_FDT
+</code>
-^ Description ^ Status ^ Comments ^
+This creates the dtc compiler utility and FDT-enabled loader(8).
-| dtc: build on %%FreeBSD%% host, integrate with build system, test compile example device tree sources, verify | Complete. Changes for yacc/lex compatiblity merged upstream. | Minor adjustments were required for the dtc to build with yacc (default in %%FreeBSD%% base installation) instead of bison. All 1248 cases from the testsuite attached to the dtc package pass. |
-| libfdt: integrate with build system | Complete. |  |
+===== Build FDT-enabled kernel =====
-| loader(8) extensions: device tree blob handling, commands to run-time modify the device tree properties, nodes etc. | Complete. |  |
-| Handling of embedded device tree blob (statically included in the kernel image, for configurations when loader(8) cannot be run) | Preliminary version working. | Tested with Marvell DB boards. |
+Enable support in the kernel, make sure the sys/arm/conf/SHEEVAPLUG kernel config file has the following entries:
-| Implementation of the ofw_bus I/F for the FDT back-end: integrate libfdt library in the kernel, potentially extend the ofw_bus framework | Complete. | All required OF_* routines work; user space interface (/dev/openfirm) works; device tree inspection with ofwdump(8) is possible. |
-| Integration of the FDT support layer with newbus infrastructure | Complete. | Tested on MPC85XX %%PowerPC%% and DB-88F6281 ARM. |
+<code>
-| Device tree handling in machdep | Complete. |  |
+# Enable FDT support.
-| Provide device tree sources for selected platforms: compile into blob, test basic parsing, debug. | Imported complete MPC8555CDS and MPC8572DS device tree source files, developed from scratch the DTS files for DB-88F6281, DB-88F5281, DB-88F5182, DB-78100 and SheevaPlug |  |
+options        FDT
-| Convert drivers attachment code to use OF-like interface (MPC85xx %%PowerPC%%, Marvell ARM) | Converted %%PowerPC%% MPC85XX drivers [attachments] to the FDT/simplebus convention: all but PCI bridge. Converted ARM Marvell drivers to the FDT/simplebus convention: all but PCI bridge. |  |
+makeoptions    FDT_DTS_FILE=sheevaplug.dts
-| Documentation: device bindings, conventions, example sources; wiki, man | Ongoing -- this wiki pages are part of this item! |  |
+options        FDT_DTB_STATIC
+</code>
+<code>
+$ make buildkernel TARGET_ARCH=arm KERNCONF=SHEEVAPLUG
+</code>
+The kernel build process includes creation (compilation) of the DTS file into a binary form (DTB), so no explicit steps are required to produce the device tree blob.
+===== Boot =====
+The kernel with statically embedded DTB does not require any additional handling and is ready to be bootstrapped in a standard way.
+====== Definitions ======
+===== Device tree source (DTS) =====
+The device tree source is a text file which describes hardware resources of a computer system in a human-readable form. See [[FlattenedDeviceTree/example.dts|example snippets]] of a device tree source (DTS) featuring description of all major components (CPU, memory, system-on-chip peripherals, IRQ assignments etc.) as device tree nodes and their properties.
+The default locations of DTS files are the following subdirectories of the %%FreeBSD%% source repository:
+<code>
+sys/dts
+sys/gnu/dts
+</code>
+===== Device tree blob (DTB) =====
+For regular use case the textual device tree description (DTS file) is first converted (compiled) into a binary object (the device tree blob i.e. the DTB), which is handed over to the final consumer (kernel) for parsing and processing of its contents.
+===== Tools, environment =====
+==== Device tree compiler (dtc) ====
+A stand-alone tool executed on the host, which transforms (compiles) a textual description of a device tree (DTS) into a binary object (DTB).
+==== Supporting library (libfdt) ====
+Helper library providing basic routines for parsing the device tree blob and retrieving data. It is integral part of the //dtc// tool, and can be used in any other code which needs to process the DTB.
+In %%FreeBSD%% for FDT-enabled platforms, //libfdt// is therefore also used by loader(8) and kernel for accessing the device tree blob.
+====== Building the dtc tool ======
+===== FreeBSD buildworld WITH_FDT =====
+The typical way of building the device tree compiler is supplying WITH_FDT setting during buildworld procedure, either via src.conf(5) or manually.
+Note the dtc tool has to be built at bootstrap tools building stage of the buildworld procedure, because the build host is not guaranteed to have the compiler installed and readily available. This is similar to other elementary tools required during further stages of the build process (like config, make and others).
+<code>
+$ cd $SRC
+$ make buildworld -DWITH_FDT
+</code>
+Note the WITH_FDT setting is turned on by default for ARM and %%PowerPC%%. In order to opt out FDT support on these platforms supply WITHOUT_FDT during buildworld procedure.
+====== Building FDT-enabled kernel ======
+In order to run a kernel driven by a flattened device tree configuration, there are two required items:
+  * FDT support enabled in the kernel
+  * accompanying device tree blob (DTB), dedicated for the given platform
+The DTB can either be statically embedded as part of the kernel image or a stand alone file, explicitly loaded and handled by loader(8).
+===== Kernel options =====
+There are a couple of %%FreeBSD%% kernel options available to manage FDT support.
+<code>
+# Flattened Device Tree (FDT) support.
+#
+# Enable FDT support.
+options        FDT
+# Provide a preferred (default) device tree source (DTS) file for the kernel.
+# The indicated DTS file will be converted (compiled) into a binary form
+# during kernel build stage.
+makeoptions    FDT_DTS_FILE=board.dts
+# Statically embed device tree blob (DTB) into a kernel image. This option
+# allows using device tree on platforms which do not (cannot) run loader(8);
+# in these cases we need to embed the DTB as part of kernel data. This option
+# requires a DTS file to be specified with FDT_DTS_FILE makeoption.
+options        FDT_DTB_STATIC
+</code>
+Note the FDT_DTS_FILE parameter is a file name specified relative to one of the default directories:
+<code>
+sys/dts
+sys/gnu/dts
+</code>
+Currently the build system can accept DTS files only from these locations.
+===== Stand-alone DTB =====
+On platforms capable of running loader(8) the default scenario is to use a stand-alone DTB file, which is handled by the loader and handed over to kernel at boot time. In this approach, a DTB should be created at kernel build time:
+  * If FDT_DTS_FILE is specified in the kernel config file, the DTB is compiled automatically as part of the //buildkernel// stage. The user does not have to perform any explicit steps.
+  * If the default DTS file is not specified in the kernel config file, the DTB needs to be created separately by the user with the //builddtb// target:
+<code>
+$ make builddtb FDT_DTS_FILE=mpc8572ds.dts
+</code>
+===== Statically embedded DTB =====
+Platforms without loader(8) support need to include the DTB file as integral part of the kernel image. For this case the FDT_DTB_STATIC option needs to be supplied in kernel config, as well as the FDT_DTS_FILE makeoption (which becomes mandatory in this scenario). At the //buildkernel// time the DTB file is automatically created from the specified DTS and embedded in the kernel without any user assistance.
+====== Installing FDT-enabled kernel ======
+The kernel installation procedure is no different for an FDT-enabled kernel: standard //installkernel// procedure applies. However, for the stand-alone DTB approach (non-static) there are caveats regarding DTB file installation:
+  * In case the default DTS file was specified in the kernel config with FDT_DTS_FILE option at build time, the according DTB file is installed automatically by the //installkernel// target, and no explicit assistance from the user is required. The DTB will be available from /sys/boot/kernel directory on the target file system.
+  * If the DTB was created manually, it has to be transferred by hand to the /sys/boot/kernel of the target file system.
+====== Running FDT-enabled kernel ======
+===== Using loader(8) =====
+==== Basic usage ====
+The following loader(8) commands are available for the device tree support
+<code>
+fdt cd <fdt_path>
+fdt header
+fdt ls [fdt_path]
+fdt mknode [fdt_path/]<node_name>
+fdt mkprop [node_path/]<property_name> <string | [ byte1 byte2 .. ] | <uint32_1 uint32_2 .. > >
+fdt prop [node_path/[prop_name value_to_set]]
+fdt pwd
+fdt rm [node_path/]<node_name | property_name>
+</code>
+=== Load blob ===
+<code>
+loader> load -t dtb boot/mpc8555cds.dtb
+loader> lsmod
+ ...
+x162f92c: boot/mpc8555cds.dtb (dtb, 0x1eb2)
+loader>
+</code>
+=== Inspect blob header ===
+<code>
+loader> fdt header
+Flattened device tree header (0x162f92c):
+ magic                   = 0xd00dfeed
+ size                    = 7858
+ off_dt_struct           = 0x00000038
+ off_dt_strings          = 0x000018ac
+ off_mem_rsvmap          = 0x00000028
+ version                 = 17
+ last compatible version = 16
+ boot_cpuid              = 0
+ size_dt_strings         = 518
+ size_dt_struct          = 6260
+loader>
+</code>
+=== List the device tree ===
+<code>
+loader> fdt ls
+/aliases
+/cpus
+/cpus/PowerPC,8555@0
+/memory
+/soc8555@e0000000
+/soc8555@e0000000/ecm-law@0
+/soc8555@e0000000/ecm@1000
+/soc8555@e0000000/memory-controller@2000
+/soc8555@e0000000/l2-cache-controller@20000
+/soc8555@e0000000/i2c@3000
+/soc8555@e0000000/dma@21300
+/soc8555@e0000000/dma@21300/dma-channel@0
+/soc8555@e0000000/dma@21300/dma-channel@80
+/soc8555@e0000000/dma@21300/dma-channel@100
+/soc8555@e0000000/dma@21300/dma-channel@180
+/soc8555@e0000000/ethernet@24000
+/soc8555@e0000000/ethernet@24000/mdio@520
+/soc8555@e0000000/ethernet@24000/mdio@520/ethernet-phy@0
+/soc8555@e0000000/ethernet@24000/mdio@520/ethernet-phy@1
+/soc8555@e0000000/ethernet@24000/mdio@520/tbi-phy@11
+/soc8555@e0000000/ethernet@25000
+/soc8555@e0000000/ethernet@25000/mdio@520
+/soc8555@e0000000/ethernet@25000/mdio@520/tbi-phy@11
+/soc8555@e0000000/serial@4500
+/soc8555@e0000000/serial@4600
+/soc8555@e0000000/crypto@30000
+/soc8555@e0000000/pic@40000
+/soc8555@e0000000/cpm@919c0
+/soc8555@e0000000/cpm@919c0/muram@80000
+/soc8555@e0000000/cpm@919c0/muram@80000/data@0
+/soc8555@e0000000/cpm@919c0/brg@919f0
+/soc8555@e0000000/cpm@919c0/pic@90c00
+/pci@e0008000
+/pci@e0008000/i8259@19000
+/pci@e0009000
+loader>
+</code>
+=== Boot kernel ===
+<code>
+loader> load -t dtb boot/mpc8555cds.dtb
+loader> boot -s
+</code>
+See [[FlattenedDeviceTree/mpc8555cds.log|full booting log]].
+The **fdtbus** and **simplebus** devices represent FDT hierarchy translated into newbus paradigm:
+<code>
+# devinfo
+nexus0
+  fdtbus0
+    lbc0
+      cfi0
+        cfid0
+      cfi1
+        cfid1
+      rtc0
+    simplebus0
+      i2c0
+        iicbus0
+          iic0
+      tsec0
+        miibus0
+          ciphy0
+      tsec1
+        miibus1
+          ciphy1
+      uart0
+      uart1
+      sec0
+      openpic0
+#
+</code>
+==== More powerful use cases ====
+=== Display node properties ===
+<code>
+loader> fdt prop /soc8555@e0000000
+#address-cells = <0x00000001>
+#size-cells = <0x00000001>
+device_type = "soc"
+compatible = "simple-bus"
+ranges = <0x00000000 0xe0000000 0x00100000>
+bus-frequency = <0x00000000>
+loader>
+</code>
+=== Change existing property value ===
+<code>
+loader> fdt prop /cpus/PowerPC,8572@0
+device_type = "cpu"
+reg = <0x00000000>
+d-cache-line-size = <0x00000020>
+i-cache-line-size = <0x00000020>
+d-cache-size = <0x00008000>
+i-cache-size = <0x00008000>
+timebase-frequency = <0x00000000>
+bus-frequency = <0x23c34600>
+clock-frequency = <0x00000000>
+next-level-cache = <0x00000001>
+</code>
+<code>
+loader> fdt prop /cpus/PowerPC,8572@0/clock-frequency <15000000>
+</code>
+<code>
+loader> fdt prop /cpus/PowerPC,8572@0
+...
+clock-frequency = <0x00e4e1c0>
+...
+</code>
+=== Remove property ===
+<code>
+loader> fdt prop /aliases
+ethernet0 = "/soc8572@ffe00000/ethernet@24000"
+ethernet1 = "/soc8572@ffe00000/ethernet@25000"
+ethernet2 = "/soc8572@ffe00000/ethernet@26000"
+ethernet3 = "/soc8572@ffe00000/ethernet@27000"
+serial0 = "/soc8572@ffe00000/serial@4500"
+serial1 = "/soc8572@ffe00000/serial@4600"
+pci0 = "/pcie@ffe08000"
+pci1 = "/pcie@ffe09000"
+pci2 = "/pcie@ffe0a000"
+</code>
+<code>
+loader> fdt rm /aliases/pci2
+</code>
+<code>
+loader> fdt prop /aliases
+ethernet0 = "/soc8572@ffe00000/ethernet@24000"
+ethernet1 = "/soc8572@ffe00000/ethernet@25000"
+ethernet2 = "/soc8572@ffe00000/ethernet@26000"
+ethernet3 = "/soc8572@ffe00000/ethernet@27000"
+serial0 = "/soc8572@ffe00000/serial@4500"
+serial1 = "/soc8572@ffe00000/serial@4600"
+pci0 = "/pcie@ffe08000"
+pci1 = "/pcie@ffe09000"
+</code>
+=== Add property to a node ===
+<code>
+loader> fdt mkprop /aliases/pci2 "/pcie@ffe0a000"
+</code>
+<code>
+loader> fdt prop /aliases
+pci2 = "/pcie@ffe0a000"
+ethernet0 = "/soc8572@ffe00000/ethernet@24000"
+ethernet1 = "/soc8572@ffe00000/ethernet@25000"
+ethernet2 = "/soc8572@ffe00000/ethernet@26000"
+ethernet3 = "/soc8572@ffe00000/ethernet@27000"
+serial0 = "/soc8572@ffe00000/serial@4500"
+serial1 = "/soc8572@ffe00000/serial@4600"
+pci0 = "/pcie@ffe08000"
+pci1 = "/pcie@ffe09000"
+</code>
+=== Add node ===
+<code>
+loader> fdt ls
+/aliases
+/cpus
+/cpus/PowerPC,8572@0
+/cpus/PowerPC,8572@1
+/memory
+/localbus@ffe05000
+/localbus@ffe05000/nor@0,0
+/localbus@ffe05000/nor@0,0/ramdisk@0
+...
+</code>
+<code>
+loader> fdt mknode /chosen
+</code>
+<code>
+loader> fdt ls
+/chosen
+/aliases
+/cpus
+/cpus/PowerPC,8572@0
+/cpus/PowerPC,8572@1
+/memory
+/localbus@ffe05000
+/localbus@ffe05000/nor@0,0
+/localbus@ffe05000/nor@0,0/ramdisk@0
+...
+</code>
+=== Remove node from the device tree ===
+<code>
+loader> fdt rm /chosen
+</code>
+<code>
+loader> fdt ls
+/aliases
+/cpus
+/cpus/PowerPC,8572@0
+/cpus/PowerPC,8572@1
+/memory
+/localbus@ffe05000
+/localbus@ffe05000/nor@0,0
+/localbus@ffe05000/nor@0,0/ramdisk@0
+...
+</code>
+===== Direct kernel boot =====
+<code>
+Marvell>> tftpboot 900000 sheevaplug/kernel.bin
+Using egiga0 device
+TFTP from server 10.0.0.204; our IP address is 10.0.2.26
+Filename 'sheevaplug/kernel.bin'.
+Load address: 0x900000
+Loading: #################################################################
+         #################################################################
+         #################################################################
+         #################################################################
+         #################################################################
+         #################################################################
+         #################################################################
+         #################################################################
+         ########################################
+done
+Bytes transferred = 2864724 (2bb654 hex)
+Marvell>> go 900000
+</code>
+====== User space access to the device tree ======
+From the device tree perspective, an FDT-driven platform is not very much different than a genuine Open Firmware. The user can inspect the device tree with //ofwdump(8)// command in base. The FDT is internally hooked into kernel ofw_bus infrastructure, so it is accessible to user process through the /dev/openfirm node.
+<code>
+# ls -al /dev/openfirm
+crw-------  1 root  wheel    0,  24 Jan  1 00:00 /dev/openfirm
+</code>
+===== List all devices in the tree =====
+<code>
+# ofwdump -a
+Node 0xc06309a0:
+  Node 0xc0630a04: aliases
+  Node 0xc0630b04: cpus
+    Node 0xc0630b30: PowerPC,8555@0
+  Node 0xc0630bec: memory
+  Node 0xc0630c24: soc8555@e0000000
+    Node 0xc0630cac: ecm-law@0
+    Node 0xc0630cfc: ecm@1000
+    Node 0xc0630d6c: memory-controller@2000
+    Node 0xc0630dec: l2-cache-controller@20000
+    Node 0xc0630ea4: i2c@3000
+    Node 0xc0630f40: dma@21300
+      Node 0xc0630fd8: dma-channel@0
+      Node 0xc0631074: dma-channel@80
+      Node 0xc0631110: dma-channel@100
+      Node 0xc06311ac: dma-channel@180
+    Node 0xc063124c: ethernet@24000
+      Node 0xc0631360: mdio@520
+        Node 0xc06313c4: ethernet-phy@0
+        Node 0xc063143c: ethernet-phy@1
+        Node 0xc06314b4: tbi-phy@11
+    Node 0xc0631504: ethernet@25000
+      Node 0xc0631618: mdio@520
+        Node 0xc0631678: tbi-phy@11
+    Node 0xc06316c8: serial@4500
+    Node 0xc063175c: serial@4600
+    Node 0xc06317f0: crypto@30000
+    Node 0xc0631898: pic@40000
+    Node 0xc0631930: cpm@919c0
+      Node 0xc06319a8: muram@80000
+        Node 0xc06319f0: data@0
+      Node 0xc0631a40: brg@919f0
+      Node 0xc0631aa8: pic@90c00
+  Node 0xc0631b58: pci@e0008000
+    Node 0xc0631fa8: i8259@19000
+  Node 0xc0632068: pci@e0009000
+#
+</code>
+===== List properties of a given node =====
+<code>
+# ofwdump -p /soc8555
+Node 0xc0630c24: soc8555@e0000000
+  #address-cells:
+00 00 01
+  #size-cells:
+00 00 01
+  device_type:
+6f 63 00
+    'soc'
+  compatible:
+69 6d 70 6c 65 2d 62 75 73 00
+    'simple-bus'
+  ranges:
+00 00 00 e0 00 00 00 00 10 00 00
+  bus-frequency:
+00 00 00
+#
+</code>
+<code>
+# ofwdump -p /soc8555/ethernet@24000
+Node 0xc063124c: ethernet@24000
+  #address-cells:
+00 00 01
+  #size-cells:
+00 00 01
+  cell-index:
+00 00 00
+  device_type:
+e 65 74 77 6f 72 6b 00
+    'network'
+  model:
+53 45 43 00
+    'TSEC'
+  compatible:
+69 61 6e 66 61 72 00
+    'gianfar'
+  reg:
+02 40 00 00 00 10 00
+  ranges:
+00 00 00 00 02 40 00 00 00 10 00
+  local-mac-address:
+00 00 00 00 00
+  interrupts:
+00 00 1d 00 00 00 02 00 00 00 1e 00 00 00 02 00 00 00 22
+00 00 02
+  interrupt-parent:
+00 00 02
+  tbi-handle:
+00 00 03
+  phy-handle:
+00 00 04
+#
+</code>
+===== Dump dts from loaded dtb =====
+There is another option in case you want to see the DTS you booted with:
+<code>
+# sysctl -b hw.fdt.dtb | dtc -I dtb
+</code>
+====== Advanced topics ======
+===== How to convert a platform to FDT =====
+==== Create DTS ====
+  * compile, inspect everything is fine
+If the dtc has to be (re)built for whatever reason manually, it can be achieved similar to any other user land applications of the base %%FreeBSD%% system. In this case:
+<code>
+$ cd gnu/usr.bin/dtc/
+$ make
+...
+</code>
+<code>
+$ ./dtc -v
+Version: DTC 1.2.0-g46b8d261
+</code>
+<code>
+$ ./dtc -h
+Usage:
+	dtc [options] <input file>
+Options:
+	-h
+		This help text
+	-q
+		Quiet: -q suppress warnings, -qq errors, -qqq all
+	-I <input format>
+		Input formats are:
+			dts - device tree source text
+			dtb - device tree blob
+			fs - /proc/device-tree style directory
+	-o <output file>
+	-O <output format>
+		Output formats are:
+			dts - device tree source text
+			dtb - device tree blob
+			asm - assembler source
+	-V <output version>
+		Blob version to produce, defaults to 17 (relevant for dtb
+		and asm output only)
+	-R <number>
+		Make space for <number> reserve map entries (relevant for
+		dtb and asm output only)
+	-S <bytes>
+		Make the blob at least <bytes> long (extra space)
+	-p <bytes>
+		Add padding to the blob of <bytes> long (extra space)
+	-b <number>
+		Set the physical boot cpu
+	-f
+		Force - try to produce output even if the input tree has errors
+	-v
+		Print DTC version and exit
+</code>
+<code>
+$ ./dtc -O dtb -o mpc8555cds.dtb -b 0 -p 1024 mpc8555cds.dts
+DTC: dts->dtb  on file "mpc8555cds.dts"
+$ file mpc8555cds.dtb
+mpc8555cds.dtb: data
+</code>
+<code>
+$ hexdump -C mpc8555cds.dtb
+00000000  d0 0d fe ed 00 00 1e b2  00 00 00 38 00 00 18 ac  |...........8....|
+00000010  00 00 00 28 00 00 00 11  00 00 00 10 00 00 00 00  |...(............|
+00000020  00 00 02 06 00 00 18 74  00 00 00 00 00 00 00 00  |.......t........|
+00000030  00 00 00 00 00 00 00 00  00 00 00 01 00 00 00 00  |................|
+00000040  00 00 00 03 00 00 00 0b  00 00 00 00 4d 50 43 38  |............MPC8|
+00000050  35 35 35 43 44 53 00 00  00 00 00 03 00 00 00 16  |555CDS..........|
+00000060  00 00 00 06 4d 50 43 38  35 35 35 43 44 53 00 4d  |....MPC8555CDS.M|
+00000070  50 43 38 35 78 78 43 44  53 00 00 00 00 00 00 03  |PC85xxCDS.......|
+00000080  00 00 00 04 00 00 00 11  00 00 00 01 00 00 00 03  |................|
+00000090  00 00 00 04 00 00 00 20  00 00 00 01 00 00 00 01  |....... ........|
+a0  61 6c 69 61 73 65 73 00  00 00 00 03 00 00 00 21  |aliases........!|
+...
+</code>
+==== Use FDT infrastrusture ====
+  * fdtbus
+  * simplebus
+==== Convert individual components (drivers) ====
+===== Recommended practices =====
+==== New bindings definitions ====
 ====== References ======
-[[http://ols.fedoraproject.org/OLS/Reprints-2008/likely2-reprint.pdf|A Symphony of Flavours: Using the device tree to describe embedded hardware.]]
+[[http://www.bsdcan.org/2010/schedule/events/171.en.html|Flattened Device Trees for Embedded FreeBSD.]]
+  * [[http://www.bsdcan.org/2010/schedule/attachments/143_FreeBSD_FDT-paper.pdf|Paper]]
+  * [[http://www.bsdcan.org/2010/schedule/attachments/136_FreeBSD_FDT-slides.pdf|Slides]]
 [[http://www.power.org/resources/downloads/Power_ePAPR_APPROVED_v1.0.pdf|Embedded Power Architecture Platform Requirements (ePAPR)]]
@@ Line 60: / Line 699: @@
 [[http://ozlabs.org/~dgibson/papers/dtc-paper.pdf|Device trees everywhere]]
-[[http://git.jdl.com/gitweb/?p=dtc.git;a=summary|The Device Tree Compiler]]
-[[http://fdt.secretlab.ca|FDT bindings definitions]]
 [[http://lists.ozlabs.org/pipermail/devicetree-discuss/|Archives of the devicetree-discuss mailing list]]
 [[http://elinux.org/Device_Trees|eLinux Device Trees wiki]]
+----
+{{tag>Project}}