uEnv.txt

optargs=run_hardware_tests quiet
mmcroot=/dev/mmcblk0p2 ro
mmcrootfstype=ext4 rootwait fixrtc

#To boot old v3.2.x based kernel enable: (BeagleBone only)
uenvcmd=run loaduimage; run mmc_classic_boot

#To boot new v3.8.x/v3.12.x based device tree:
#uenvcmd=run loaduimage; run loadfdt; run mmcargs; bootz ${loadaddr} - ${fdtaddr}