A word of comment...
At least some of the Linaro file system images are running irqbalance daemon, which will most likely play with MMC and USB interrupts affiliation in runtime. To prevent it from doing so, /etc/default/irqbalance should contain this line:
export IRQBALANCE_BANNED_INTERRUPTS="41 42 48"
Sounds like a job for the VE hwpack, I guess?
Cheers!
Paweł