Merge branch 'master' of git://git.denx.de/u-boot-sunxi

[u-boot] / doc / README.fdt-control

diff --git a/doc/README.fdt-control b/doc/README.fdt-control
index 85bda035043497d8d23aed8a436e24d630c60937..634a10616fc071dd1aab0b227f77fbc28c4435ab 100644 (file)
--- a/doc/README.fdt-control
+++ b/doc/README.fdt-control
@@ -1,24 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0+
 #
 # Copyright (c) 2011 The Chromium OS Authors.
-#
-# See file CREDITS for list of people who contributed to this
-# project.
-#
-# This program is free software; you can redistribute it and/or
-# modify it under the terms of the GNU General Public License as
-# published by the Free Software Foundatio; either version 2 of
-# the License, or (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, write to the Free Software
-# Foundation, Inc., 59 Temple Place, Suite 330, Boston,
-# MA 02111-1307 USA
-#
 
 Device Tree Control in U-Boot
 =============================
@@ -76,11 +58,11 @@ Tools
 
 To use this feature you will need to get the device tree compiler here:
 
-       git://jdl.com/software/dtc.git
+       git://git.kernel.org/pub/scm/utils/dtc/dtc.git
 
 For example:
 
-       $ git clone git://jdl.com/software/dtc.git
+       $ git clone git://git.kernel.org/pub/scm/utils/dtc/dtc.git
        $ cd dtc
        $ make
        $ sudo make install
@@ -99,7 +81,8 @@ Then run the compiler (your version will vary):
        *   Bad configuration:  0
        * Strange test result:  0
 
-You will also find a useful ftdump utility for decoding a binary file.
+You will also find a useful fdtdump utility for decoding a binary file, as
+well as fdtget/fdtput for reading and writing properties in a binary file.
 
 
 Where do I get an fdt file for my board?
@@ -128,11 +111,11 @@ file into
        board/<vendor>/dts/<name>.dts
 
 This should include your CPU or SOC's device tree file, placed in
-arch/<arch>/dts, and then make any adjustments required. The name of this
-is CONFIG_ARCH_DEVICE_TREE.dts.
+arch/<arch>/dts, and then make any adjustments required.
 
 If CONFIG_OF_EMBED is defined, then it will be picked up and built into
-the U-Boot image (including u-boot.bin).
+the U-Boot image (including u-boot.bin). This is suitable for debugging
+and development only and is not recommended for production devices.
 
 If CONFIG_OF_SEPARATE is defined, then it will be built and placed in
 a u-boot.dtb file alongside u-boot.bin. A common approach is then to
@@ -140,9 +123,28 @@ join the two:
 
        cat u-boot.bin u-boot.dtb >image.bin
 
-and then flash image.bin onto your board.
+and then flash image.bin onto your board. Note that U-Boot creates
+u-boot-dtb.bin which does the above step for you also. If you are using
+CONFIG_SPL_FRAMEWORK, then u-boot.img will be built to include the device
+tree binary.
+
+If CONFIG_OF_BOARD is defined, a board-specific routine will provide the
+device tree at runtime, for example if an earlier bootloader stage creates
+it and passes it to U-Boot.
 
-You cannot use both of these options at the same time.
+If CONFIG_OF_HOSTFILE is defined, then it will be read from a file on
+startup. This is only useful for sandbox. Use the -d flag to U-Boot to
+specify the file to read.
+
+You cannot use more than one of these options at the same time.
+
+To use a device tree file that you have compiled yourself, pass
+EXT_DTB=<filename> to 'make', as in:
+
+       make EXT_DTB=boot/am335x-boneblack-pubkey.dtb
+
+Then U-Boot will copy that file to u-boot.dtb, put it in the .img file
+if used, and u-boot-dtb.bin.
 
 If you wish to put the fdt at a different address in memory, you can
 define the "fdtcontroladdr" environment variable. This is the hex
@@ -150,12 +152,23 @@ address of the fdt binary blob, and will override either of the options.
 Be aware that this environment variable is checked prior to relocation,
 when only the compiled-in environment is available. Therefore it is not
 possible to define this variable in the saved SPI/NAND flash
-environment, for example (it will be ignored).
+environment, for example (it will be ignored). After relocation, this
+variable will be set to the address of the newly relocated fdt blob.
+It is read-only and cannot be changed. It can optionally be used to
+control the boot process of Linux with bootm/bootz commands.
 
 To use this, put something like this in your board header file:
 
 #define CONFIG_EXTRA_ENV_SETTINGS      "fdtcontroladdr=10000\0"
 
+Build:
+
+After board configuration is done, fdt supported u-boot can be build in two ways:
+1)  build the default dts which is defined from CONFIG_DEFAULT_DEVICE_TREE
+    $ make
+2)  build the user specified dts file
+    $ make DEVICE_TREE=<dts-file-name>
+
 
 Limitations
 -----------