Please consider the following patches (in this order) for backporting to v6.6 and newer.
fb318ca0a522295edd6d796fb987e99ec41f0ee5 ae835a96d72cd025421910edb0e8faf706998727
The second patch addresses a regression on older Dell hardware. The first one is a prerequisite for the second one, and a minor bugfix itself.
Thanks, Ard.