Commit 82f766d1 authored by Alex Deymo's avatar Alex Deymo Committed by Tom Rini

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: default avatarAlex Deymo <>
Reviewed-by: Simon Glass's avatarSimon Glass <>
parent 45a6d231
......@@ -968,7 +968,7 @@ The following options need to be configured:
tree is available in the global data as gd->fdt_blob.
U-Boot needs to get its device tree from somewhere. This can
be done using one of the two options below:
be done using one of the three options below:
If this variable is defined, U-Boot will embed a device tree
......@@ -989,6 +989,12 @@ The following options need to be configured:
still use the individual files if you need something more
If this variable is defined, U-Boot will use the device tree
provided by the board at runtime instead of embedding one with
the image. Only boards defining board_fdt_blob_setup() support
this option (see include/fdtdec.h file).
- Watchdog:
If this variable is defined, it enables watchdog
......@@ -470,6 +470,16 @@ int board_init(void)
return bcm2835_power_on_module(BCM2835_MBOX_POWER_DEVID_USB_HCD);
* If the firmware passed a device tree use it for U-Boot.
void *board_fdt_blob_setup(void)
if (fdt_magic(fw_dtb_pointer) != FDT_MAGIC)
return NULL;
return (void *)fw_dtb_pointer;
int ft_board_setup(void *blob, bd_t *bd)
......@@ -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.
......@@ -51,6 +51,14 @@ config OF_EMBED
and development only and is not recommended for production devices.
Boards in the mainline U-Boot tree should not use it.
config OF_BOARD
bool "Provided by the board at runtime"
depends on !SANDBOX
If this option is enabled, the device tree will be provided by
the board at runtime if the board supports it, instead of being
bundled with the image.
bool "Host filed DTB for DT control"
depends on SANDBOX
......@@ -1023,4 +1023,10 @@ int fdtdec_setup_memory_banksize(void);
int fdtdec_setup(void);
* Board-specific FDT initialization. Returns the address to a device tree blob.
* Called when CONFIG_OF_BOARD is defined.
void *board_fdt_blob_setup(void);
......@@ -1255,6 +1255,9 @@ int fdtdec_setup(void)
/* FDT is at end of image */
gd->fdt_blob = (ulong *)&_end;
# endif
# elif defined(CONFIG_OF_BOARD)
/* Allow the board to override the fdt address. */
gd->fdt_blob = board_fdt_blob_setup();
# elif defined(CONFIG_OF_HOSTFILE)
if (sandbox_read_fdt_from_file()) {
puts("Failed to read control FDT\n");
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