qemu mipsel/ls3a7a board bsp

This is for Linux Lab.

Boot it

$ ./boot.sh

If missing sdl2.0 lib, please install it at first:

$ sudo apt-get install libsdl2-2.0-0 libsdl2-image-2.0-0

Use it in Linux Lab

$ cd /path/to/linux-lab
$ make B=mipsel/ls3a7a
$ make boot