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![Stephen Warren](/assets/img/avatar_default.png)
On all Pis so far, the VC FW provides a short stub to set up the ARM CPU before entering the kernel (a/k/a U-Boot for us). This feature is not currently supported by the VC FW when booting in 64-bit mode. However, this feature will likely appear in the near future, and this U-Boot port assumes that such a feature is in place. Without that feature, or a temporary workaround described below, U-Boot will not boot. Once the VC FW does provide the ARM stub, u-boot.bin built for rpi_3 can be used drectly as kernel7.img, in the same way as any other RPi port. The following config.txt is required: # Fix mini UART input frequency, and setup/enable up the UART. # Without this option, U-Boot will not boot, even if you don't care # about the serial console. This option will always be required for # all RPi3 use-cases, unless the PL011 UART is used, which is not # yet supported by rpi_3* builds of U-Boot. enable_uart=1 # Boot in AArch64 (64-bit) mode. # It is possible that a future VC FW will remove the need for this # option, instead auto-setting 32-/64-bit mode based on the "kernel" # filename present on the SD card. arm_control=0x200 Prior to the VC FW providing the ARM boot stub, you can use the following steps to build an equivalent stub into the U-Boot binary: git clone https://github.com/swarren/rpi-3-aarch64-demo.git \ ../rpi-3-aarch64-demo (cd ../rpi-3-aarch64-demo && ./build.sh) Build U-Boot for rpi_3 in the usual way cat ../rpi-3-aarch64-demo/armstub64.bin u-boot.bin > u-boot.bin.stubbed Use u-boot.bin.stubbed as kernel7.img on the Pi SD card. In this case, the following additional entries are required in config.txt: # Tell the FW to load the kernel image at address 0, the reset vector. kernel_old=1 Signed-off-by: Stephen Warren <swarren@wwwdotorg.org> Reviewed-by: Tom Rini <trini@konsulko.com>
12 lines
256 B
Plaintext
12 lines
256 B
Plaintext
CONFIG_ARM=y
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CONFIG_ARCH_BCM283X=y
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CONFIG_TARGET_RPI_3=y
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CONFIG_OF_BOARD_SETUP=y
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CONFIG_SYS_PROMPT="U-Boot> "
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# CONFIG_CMD_IMLS is not set
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# CONFIG_CMD_FLASH is not set
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# CONFIG_CMD_FPGA is not set
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CONFIG_CMD_GPIO=y
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CONFIG_PHYS_TO_BUS=y
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CONFIG_OF_LIBFDT=y
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