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# 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](http://www.qemu.org/) 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.
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