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authorAlex Deymo <deymo@google.com>2017-04-02 01:25:20 -0700
committerTom Rini <trini@konsulko.com>2017-05-09 20:35:06 -0400
commit82f766d1d2c580a29bed340ea4dd9fa1b8ff05e0 (patch)
tree81c70f6e469d4431d3852e2d6fe43443fff6ad5a /doc
parent45a6d231b2f9b891a7df517fc40b8466e12f2b57 (diff)
Allow boards to initialize the DT at runtime.
In some boards like the Raspberry Pi the initial bootloader will pass a DT to the kernel. When using U-Boot as such kernel, the board code in U-Boot should be able to provide U-Boot with this, already assembled device tree blob. This patch introduces a new config option CONFIG_OF_BOARD to use instead of CONFIG_OF_EMBED or CONFIG_OF_SEPARATE which will initialize the DT from a board-specific funtion instead of bundling one with U-Boot or as a separated file. This allows boards like the Raspberry Pi to reuse the device tree passed from the bootcode.bin and start.elf firmware files, including the run-time selected device tree overlays. Signed-off-by: Alex Deymo <deymo@google.com> Reviewed-by: Simon Glass <sjg@chromium.org>
Diffstat (limited to 'doc')
-rw-r--r--doc/README.fdt-control4
1 files changed, 4 insertions, 0 deletions
diff --git a/doc/README.fdt-control b/doc/README.fdt-control
index c9656299053..378b06b108d 100644
--- a/doc/README.fdt-control
+++ b/doc/README.fdt-control
@@ -130,6 +130,10 @@ 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
specify the file to read.