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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 NPCM8xx-based machine.
+
+## Building
+
+If you have a 64-bit ARM compiler installed as `aarch64-linux-gnu-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=aarch64-linux-gnueabi-
+```
+
+If either case is successful, a `npcm8xx_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-aarch64 -machine npcm845-evb -nographic \
+    -bios "${IMAGES}/npcm8xx_bootrom.bin"
+    -drive file="${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.