isabella232 / vbootrom

Virtual Boot ROM for NPCM7xx SoCs

This is not an officially supported Google product.

This is a super simple Boot ROM that is intended to be used as a -bios image for QEMU when emulating an NPCM7xx-based machine.

Building

If you have a 32-bit ARM compiler installed as arm-none-eabi-gcc, simply run make.

If your ARM compiler has a different name, you'll need to override the CROSS_COMPILE prefix, e.g. like this:

make CROSS_COMPILE=arm-linux-gnueabi-

If either case is successful, a npcm7xx_bootrom.bin file will be produced.

Using

The Boot ROM image may be passed to a QEMU system emulator using the -bios option. For example like this:

qemu-system-arm -machine quanta-gsj -nographic \
    -bios "${IMAGES}/npcm7xx_bootrom.bin"
    -drive file="${IMAGES}/image-bmc,if=mtd,bus=0,unit=0,format=raw,snapshot=on"

Limitations

• Secure boot is not supported.
• Only booting from offset 0 of the flash at SPI0 CS0 is implemented.
• Fallback images (if the first image doesn't boot) are not implemented.
• Exception vectors are copied to SRAM, but not remapped.
• Most OTP bits and straps are not honored.
• The reset type bits are not updated.
• OTP protection is not implemented.
• No clock initialization is performed.
• UART programming protocol is not implemented.
• Host notification through the PCI mailbox is not implemented.
• Most fields in the ROM status structure are not set.