For SWD (instead of normal JTAG) you need a different CPLD "buffer logic" image on the Bus Blaster, the KT-Link compatible ones seem like the recommended means.
# with buffer logic at https://github.com/dergraaf/busblaster_v4/blob/master/ktlink/ktlink.svf
# via http://dangerousprototypes.com/forum/viewtopic.php?f=37&t=5954 from https://github.com/mchck/mchck/wiki/Getting-Started#wiki-bus-blaster
curl -O https://github.com/dergraaf/busblaster_v4/raw/master/ktlink/ktlink.svf
openocd -f board/dp_busblaster_v3.cfg -c "adapter_khz 1000; init; svf /Users/natevw/Downloads/ktlink.svf; shutdown"