Linux Preparing To Deal With SD Card Power/Performance Features
Ulf Hansson of Linaro sent out patches this week so the Linux kernel begins reading/parsing those SD extension registers. However, at this point the Linux kernel isn't making use of those power/performance registers... Hopefully those patches will come soon now that this prerequisite work to actually read those registers is in place by these patches.
SD 4.0 adds features for power off notification, power down mode, and power sustenance. The performance features with SD 6.0 are around self-maintenance, caching, and command queuing.
These Linux kernel patches are out for review on the kernel mailing list. Stay tuned for when the complete support arrives for improving the SD card support on the mainline Linux kernel but a bit surprising and unfortunate this support didn't materialize sooner.