Comment 36 for bug 1668105

Hi I have a very similar issue I use Debian with kernel 4.5 in a macbook pro 12.1
boot take a long time before show grub, but when it appear the keyboard is almost useless... you have a "windows time" where the keyboard respond this "windows" are random, they come and go, the best opportunity is press enter key before grub pops up (with this boot with default entry) this erratic behavior is present in all "special boot options" of the macbook pro (see https://support.apple.com/en-us/HT201255) the touch pad have the same problems. One of this special boot options (pressing "D") is a hardware diagnostics in this test my card reader show an error VDC001. On OSX the card reader work fine, but Debian cannot see it.

Olivier can you do a hardware test? turn on your Mac with the D key pressed.