armv8: configs: ls1012a: correct the generic timer frequency

[people/ms/u-boot.git] / doc / README.fdt-control

diff --git a/doc/README.fdt-control b/doc/README.fdt-control
index 0ceebe7aa6f959fb901a21a45931ee245836eac7..378b06b108d9e8bb7c834d585f0e1342eb7b0f46 100644 (file)
--- a/doc/README.fdt-control
+++ b/doc/README.fdt-control
@@ -33,12 +33,6 @@ the features of each board in the device tree file, and have a single
 generic source base.
 
 To enable this feature, add CONFIG_OF_CONTROL to your board config file.
-It is currently supported on ARM, x86 and Microblaze - other architectures
-will need to add code to their arch/xxx/lib/board.c file to locate the
-FDT. Alternatively you can enable generic board support on your board
-(with CONFIG_SYS_GENERIC_BOARD) if this is available (as it is for
-PowerPC). For ARM, Tegra and Exynos5 have device trees available for
-common devices.
 
 
 What is a Flat Device Tree?
@@ -122,7 +116,8 @@ This should include your CPU or SOC's device tree file, placed in
 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
@@ -130,7 +125,14 @@ 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.
 
 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
@@ -138,13 +140,24 @@ 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
 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: