[PATCH 0/4][SRU][B][C][OEM-B]SATA device is not going to DEVSLP

[AceLan Kao]

BugLink: https://bugs.launchpad.net/bugs/1781533

[Impact]
Any of the platforms we’ve been seeing SATA problems not going to deepest
state leads to other devices not getting there during long idle or s2idle.
And it also prevents the system from entering deeper PC state other than
PC3.

[Fix]
Suggested from Intel and Dell to contains the following 4 commits,
and all of 4 commits are in v4.19-rc1
https://patchwork.kernel.org/patch/10502285/
https://patchwork.kernel.org/patch/10502287/
https://patchwork.kernel.org/patch/10535781/
https://patchwork.kernel.org/patch/10535783/

[Test]
Verified the power consumption on some new platforms, it improves the
SATA HDD power consumption around 0.5w during long idle.

[Regression Potential]
Low, the DEVSLP function is already validated when shipped with SLP_S0
support.

Srinivas Pandruvada (4):
  ata: ahci: Support state with min power but Partial low power state
  ata: ahci: Enable DEVSLP by default on x86 with SLP_S0
  ata: libahci: Correct setting of DEVSLP register
  ata: libahci: Allow reconfigure of DEVSLP register

 drivers/ata/ahci.c        | 38 +++++++++++++++++++++++++++++++++-----
 drivers/ata/libahci.c     | 25 ++++++++++++++++---------
 drivers/ata/libata-core.c |  1 +
 drivers/ata/libata-scsi.c |  1 +
 include/linux/libata.h    |  3 ++-
 5 files changed, 53 insertions(+), 15 deletions(-)

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2.17.1