Comment 27 for bug 1546694

This should get you going with the 4.2 kernel

wget https://www.dropbox.com/s/y4c8nm8fr1f2amx/bluetooth-4.2.tar.gz
tar -zxvf bluetooth-4.2.tar.gz
cd bluetooth
cp /usr/src/linux-headers-`uname -r`/.config ./
make -C /lib/modules/$(uname -r)/build M=$(pwd) modules
sudo cp btusb.ko /lib/modules/$(uname -r)/kernel/drivers/bluetooth/
sudo cp ath3k.ko /lib/modules/$(uname -r)/kernel/drivers/bluetooth/

Reboot and as long as you have already

wget http://download.windowsupdate.com/d/msdownload/update/driver/drvs/2014/01/20623393_919a4673931aa789f0b1c3eeafb360b36097894a.cab
sudo cabextract 20623393_919a4673931aa789f0b1c3eeafb360b36097894a.cab -F *.dfu -d /lib/firmware/ar3k

It should work