From f4ac6476945ff62939420bcf8266e39f8d5d54bd Mon Sep 17 00:00:00 2001 From: Hans de Goede Date: Thu, 14 Sep 2017 12:35:36 +0200 Subject: libata: Add new med_power_with_dipm link_power_management_policy setting 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 Cc: Matthew Garrett Signed-off-by: Hans de Goede Signed-off-by: Tejun Heo --- drivers/ata/libata-core.c | 1 + 1 file changed, 1 insertion(+) (limited to 'drivers/ata/libata-core.c') diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c index ee4c1ec9dca0..65f7574afc55 100644 --- a/drivers/ata/libata-core.c +++ b/drivers/ata/libata-core.c @@ -3964,6 +3964,7 @@ int sata_link_scr_lpm(struct ata_link *link, enum ata_lpm_policy policy, scontrol &= ~(0x1 << 8); scontrol |= (0x6 << 8); break; + case ATA_LPM_MED_POWER_WITH_DIPM: case ATA_LPM_MIN_POWER: if (ata_link_nr_enabled(link) > 0) /* no restrictions on LPM transitions */ -- cgit v1.2.3-59-g8ed1b