drop low power policy board type

The series is based on top of:
https://git.kernel.org/pub/scm/linux/kernel/git/libata/linux.git/log/?h=for-next

Hello all,

This revives a patch sent out almost two years ago from Mario Limonciello:
https://lore.kernel.org/linux-ide/[email protected]/T/#u

The reason why we did not merge it back then, is because LPM and hotplug events are mutually exclusive.

The difference with this series compared to what was sent out back then:
I've added a patch that checks if the port is external, i.e. either hotplug capable or eSATA. For external ports, we never enable LPM, as that will break hotplug.

For ports that do not advertise themselves as external (typically laptops), we set the LPM policy as requested.

This matches how Microsoft Windows does things, see:
https://studylib.net/doc/10034428/esata---microsoft-center

Thanks to Werner Fischer for suggesting something like this at last year's ALPSS conference.

There might of course be some platform firmware that e.g. incorrectly marks its port as internal, even though it is external, but if we find any such platforms we will need to deal with them using quirks.

Also note that we even if the user requested a certain policy, there is no guarantee that he will get all the features for that policy, see:
https://github.com/torvalds/linux/blob/master/drivers/ata/libata-sata.c#L403-L414

However, I'd rather we not try to map all the combinations of partial/slumber/devsleep in to a single policy represented by a single integer, thus I do not try to "change" the requested policy. The user will get all the features that are included in the requested policy AND supported by the HBA.

Another difference (compared to an earlier version of Mario's series) is that we do not try to change the default CONFIG_SATA_MOBILE_LPM_POLICY value from 0 to 3, it will continue to be 0.
If you really don't want LPM even if your HBA supports it, and your port is internal, one option is to leave the Kconfig set to the default value.

Damien: considering that the Intel VMD + ahci_intel_pcs_quirk() bug turned out to have nothing to do with LPM, it was simply the fact that the ahci_intel_pcs_quirk() was only applied if there was an explicit entry in ahci_pci_tbl. So since that bug is totally unrelated to LPM, I no longer think that this series need to wait for a fix for that bug.

Link to v1:
https://lore.kernel.org/linux-ide/[email protected]/

Changes since v1:
-Picked up tags from Damien.
-Moved the comment in front of ahci_mark_external_port() to inside the
function.
-Modified the comment in patch 4/5 to more clearly state hotplug removal
events.
-Rewrote the commit message for patch 4/5 to be more detailed.

Kind regards,
Niklas

Mario Limonciello (1):
ata: ahci: Drop low power policy board type

Niklas Cassel (4):
ata: ahci: move marking of external port earlier
ata: ahci: a hotplug capable port is an external port
ata: ahci: drop hpriv param from ahci_update_initial_lpm_policy()
ata: ahci: do not enable LPM on external ports

 drivers/ata/Kconfig   |   5 +-
 drivers/ata/ahci.c    | 135 +++++++++++++++++++++++-------------------
 drivers/ata/ahci.h    |   9 +--
 drivers/ata/libahci.c |   7 ---
 4 files changed, 78 insertions(+), 78 deletions(-)

2.43.0