Hi All, On many laptops setting a different LPM policy then unknown / max_performance can lead to power-savings of 1.0 - 1.5 Watts (when idle). Modern ultrabooks idle around 6W (at 50% screen brightness), 1.0 - 1.5W is a significant chunk of this. There are some performance / latency costs to enabling LPM by default, so it is desirable to make it possible to set a different LPM policy for mobile / laptop variants of chipsets / "South Bridges" vs their desktop / server counterparts. This series adds a new ahci.mobile_lpm_policy kernel cmdline option, which defaults to a new SATA_MOBILE_LPM_POLICY Kconfig option so that Linux distributions can choose to set a LPM policy for mobile chipsets by default. I realize that this series will not be entirely uncontroversial, enabling LPM by default is not entirely without risk of regressions. At least min_power is known to cause issues with some disks, including some reports of data corruption. But this series only adds a Kconfig option to allow distributions to select a different LPM policy for mobile chipsets if they which to do so, the default value is unchanged from before. I've done a blog-post a while ago to ask users to test this and specifically the new med_power_with_dipm option which mirrors the Intel RST Windows drivers defaults: https://hansdegoede.livejournal.com/18412.html Test results from this can be found here: https://fedoraproject.org/wiki/Changes/ImprovedLaptopBatteryLife#How_To_Test All testing sofar has shown that the med_power_with_dipm option seems to be safe, even with SSDs which are known to corrupt data with the min_power setting. Taking this into account, one thing to consider is the following change to the Kconfig changes in the last patch in the series: config SATA_MOBILE_LPM_POLICY int "Default SATA Link Power Management policy for mobile chipsets" - range 0 4 + range 0 3 default 0 depends on SATA_AHCI help Thus effectively forbidding choosing min_power as default at the Kconfig level. Regards, Hans -- 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
