• Stephen Warren's avatar
    ARM: add Raspberry Pi 3 64-bit config · d22a7657
    Stephen Warren authored
    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: default avatarStephen Warren <swarren@wwwdotorg.org>
    Reviewed-by: default avatarTom Rini <trini@konsulko.com>
    d22a7657
rpi_3_defconfig 256 Bytes