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, included the run-time selected device tree overlays.

Signed-off-by: Alex Deymo deymo@google.com --- README | 8 +++++++- board/raspberrypi/rpi/rpi.c | 10 ++++++++++ doc/README.fdt-control | 4 ++++ dts/Kconfig | 8 ++++++++ include/fdtdec.h | 6 ++++++ lib/fdtdec.c | 3 +++ 6 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/README b/README index aa907ced8a..e658f02a7e 100644 --- a/README +++ b/README @@ -975,7 +975,7 @@ 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:

CONFIG_OF_EMBED If this variable is defined, U-Boot will embed a device tree @@ -996,6 +996,12 @@ The following options need to be configured: still use the individual files if you need something more exotic.

+ CONFIG_OF_BOARD + 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: CONFIG_WATCHDOG If this variable is defined, it enables watchdog diff --git a/board/raspberrypi/rpi/rpi.c b/board/raspberrypi/rpi/rpi.c index 2146534b36..ef04d397d6 100644 --- a/board/raspberrypi/rpi/rpi.c +++ b/board/raspberrypi/rpi/rpi.c @@ -516,6 +516,16 @@ int board_mmc_init(bd_t *bis) msg_clk->get_clock_rate.body.resp.rate_hz); }

+/* + * 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) { /* diff --git a/doc/README.fdt-control b/doc/README.fdt-control index c965629905..378b06b108 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. diff --git a/dts/Kconfig b/dts/Kconfig index 3f64eda619..978b2d7f3d 100644 --- a/dts/Kconfig +++ b/dts/Kconfig @@ -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 + help + 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. + config OF_HOSTFILE bool "Host filed DTB for DT control" depends on SANDBOX diff --git a/include/fdtdec.h b/include/fdtdec.h index d074478f14..5c54f71458 100644 --- a/include/fdtdec.h +++ b/include/fdtdec.h @@ -1015,4 +1015,10 @@ 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); + #endif diff --git a/lib/fdtdec.c b/lib/fdtdec.c index 81f47ef2c7..2e1beb545b 100644 --- a/lib/fdtdec.c +++ b/lib/fdtdec.c @@ -1247,6 +1247,9 @@ 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");