I confirm for Kubuntu 15.03 with 3.19.0-15-generic. With the hint #11 and #12 I could implement a workaround with discard enabled in fstab. Instead of deactivating the controller, I only disabled NCQ in /etc/default/grub:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash libata.force=noncq"
After update-grub and reboot everything seems to work.
I confirm for Kubuntu 15.03 with 3.19.0-15-generic. With the hint #11 and #12 I could implement a workaround with discard enabled in fstab. Instead of deactivating the controller, I only disabled NCQ in /etc/default/grub: LINUX_DEFAULT= "quiet splash libata.force=noncq"
GRUB_CMDLINE_
After update-grub and reboot everything seems to work.