Notable to this latest Intel DRM-Next pull request is that FBC and PSR are enabled by default... After a lot of toying with FBC over many kernel cycles, Frame-Buffer Compression is being turned on. This power-saving feature is being turned on by default for Haswell and Broadwell hardware currently.
The other power-saving feature being flipped on by default with the i915 DRM driver in Linux 4.5 is Panel Self Refesh (PSR). As I explained in an earlier article, "Panel Self Refresh has been available for a few years now via the (e)DP DisplayPort 1.3 specification from VESA. Panel Self Refresh is about reducing power consumption when the system is idling / the display is static. The idea behind Panel Self Refresh is to have the display keep using the same frame-buffer whenever the contents are unchanged, which can allow power-savings by shutting down unnecessary GPU circuitry. It's basically skipping over a lot of work for the hardware by using the same (idle) image stored by the display until new updates are sent from the GPU. PSR can be huge for laptop and mobile users if often staring at an unchanged display when reading a web-site or document or the system is simply idling. Reports from different vendors I've seen indicate the PSR power saving benefits can be anywhere from ~29% to 85% based upon the hardware and other factors."
Panel Self Refresh is being enabled by default for Haswell, Broadwell, Valley View, and Cherryview hardware.
Other changes for the Intel driver in Linux 4.6 include fixes to the hardware state readout, DC3 fixes, continued atomic code improvements, and more. All of the details for this latest Intel DRM-Next pull request can be found via this pull request. This latest pull comes on top of other changes already queued up in DRM-Next.