On Thu, Sep 14, 2017 at 12:35:36PM +0200, Hans de Goede wrote: > As described by Matthew Garret quite a while back: > https://mjg59.dreamwidth.org/34868.html > > Intel CPUs starting with the Haswell generation need SATA links to power > down for the "package" part of the CPU to reach low power-states like > PC7 / P8 which bring a significant power-saving with them. > > The default max_performance lpm policy does not allow for these high > PC states, both the medium_power and min_power policies do allow this. > > The min_power policy saves significantly more power, but there are some > reports of some disks / SSDs not liking min_power leading to system > crashes and in some cases even data corruption has been reported. > > Matthew has found a document documenting the default settings of > Intel's IRST Windows driver with which most laptops ship: > https://www-ssl.intel.com/content/dam/doc/reference-guide/sata-devices-implementation-recommendations.pdf > > Matthew wrote a patch changing med_power to match those defaults, but > that never got anywhere as some people where reporting issues with the > patch-set that patch was a part of. > > This commit is another attempt to make the default IRST driver settings > available under Linux, but instead of changing medium_power and > potentially introducing regressions, this commit adds a new > med_power_with_dipm setting which is identical to the existing > medium_power accept that it enables dipm on top, which makes it match > the Windows IRST driver settings, which should hopefully be safe to > use on most devices. > > The med_power_with_dipm setting is close to min_power, except that: > a) It does not use host-initiated slumber mode (ASP not set), > but it does allow device-initiated slumber > b) It does not enable DevSlp mode > > On my T440s test laptop I get the following power savings when idle: > medium_power 0.9W > med_power_with_dipm 1.2W > min_power 1.2W > > Suggested-by: Matthew Garrett <mjg59@xxxxxxxxxxxxx> > Cc: Matthew Garrett <mjg59@xxxxxxxxxxxxx> > Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> Applied to libata/for-4.15. Thanks. -- tejun -- 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
