Public bug reported:
In order to let CPU Package gets deeper C-state, we need to use power-
saving SATA LPM to achieve that.
This commit introduce a new config, SATA_MOBILE_LPM_POLICY:
commit ebb82e3c79d2a956366d0848304a53648bd6350b
Author: Hans de Goede <hdego...@redhat.com>
Date: Mon Dec 11 17:52:16 2017 +0100
ahci: Allow setting a default LPM policy for mobile chipsets
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. Also 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.
This commits 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.
The reason to have both a kernel cmdline option and a Kconfig default
value for it, is to allow easy overriding of the default to allow
trouble-shooting without needing to rebuild the kernel.
Signed-off-by: Hans de Goede <hdego...@redhat.com>
Signed-off-by: Tejun Heo <t...@kernel.org>
"3 => Medium power with Device Initiated PM enable" is a well-balanced
that can let Package enters deeper C-state.
Also, Fedora already set SATA_MOBILE_LPM_POLICY=3 for their latest
kernel.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: Incomplete
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https://bugs.launchpad.net/bugs/1759547
Title:
Use med_with_dipm SATA LPM to save more power for mobile platforms
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