Rework command issue/completion flow to be more like AHCI's and switch to using interrupts to detect command completion.
Rework command issue/completion flow to be more like AHCI's and switch to
using interrupts to detect command completion.

Report on command timeouts (but no recovery yet).

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars