This patchset tries to get us closer to having reasonable defaults for link power management on AHCI. Recent Intel CPUs can't enter deep power saving states unless the SATA link is in a low power state, appearing to be limited to PC6 in PARTIAL and PC7 in SLUMBER, and PC2 otherwise. This amounts to a difference of several Watts in system idle. There appear to be two components to how this is managed on Windows: 1) Firmware enables a set of power management features on platform init 2) The Intel Rapid Storage Technology AHCI driver enables a set of features As far as (1) goes, we ignore all firmware config and start from scratch. As far as (2) goes, we default to not enabling any power management features because of concerns about reliability and performance. These patches stash the firmware configuration at kernel init time, add a new policy that simply reapplies the firmware configuration and changes the semantics of the medium_power LPM configuration such that it matches the configuration enabled by the IRST driver on Windows. We can then apply udev rules that use the firmware_defaults policy in general and the medium_power policy where we expect that to work, with a view to changing the in-kernel defaults down the road if this doesn't appear to cause any problems. -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
