[patch] enable AHCI device initiated power management
Hi,
this patch
http://leaf.dragonflybsd.org/~hofmann/ahci_dipm.diff
enables device initiated AHCI link power management.
Some disks (e.g. the Intel X25-M SSD) don't support host initiated
power management.
Therefore also enable device initiated power management when
ahci power management is set to "aggressive".
This saves about 0.5W on a Thinkpad with Intel X25-M.
* Move the currently unused function ahci_pm_set_feature() to ahci.c
and make it work for ATA_SATAFT_DEVIPS.
* Use ahci_set_feature() to enable ATA_SATAFT_DEVIPS when AHCI power
management is set to "aggressive".
* Set ap->link_pwr_mgmt early in ahci_port_link_pwr_mgmt() to ensure
it is set when ahci_set_feature() -> ahci_poll() -> ahci_port_intr()
is called.
Inspired-by: Linux
Cheers,
Johannes
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