Albert, with my MacBookPro9,2 I'm able to reinstall OS X via https://support.apple.com/en-us/HT204904 to apply firmware updates, even after installing Ubuntu. Would that work for you?
Albert, with my MacBookPro9,2 I'm able to reinstall OS X via https:/ /support. apple.com/ en-us/HT204904 to apply firmware updates, even after installing Ubuntu. Would that work for you?