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| author | Hans de Goede <hdegoede@redhat.com> | 2017-09-14 12:35:36 +0200 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2017-09-18 20:22:04 -0700 |
| commit | f4ac6476945ff62939420bcf8266e39f8d5d54bd (patch) | |
| tree | 3428a2c2eeff5f7e8f63949914246add64721a90 /drivers/ata/libata-core.c | |
| parent | 23e4c67ae13da7549a54f4e8c0014f48b2ef5204 (diff) | |
| download | linux-f4ac6476945ff62939420bcf8266e39f8d5d54bd.tar.bz2 | |
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 <mjg59@srcf.ucam.org>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'drivers/ata/libata-core.c')
| -rw-r--r-- | drivers/ata/libata-core.c | 1 |
1 files changed, 1 insertions, 0 deletions
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 */ |