libata: identify and init ZPODD devices

The ODD can be enabled for ZPODD if the following three conditions are
satisfied:
1 The ODD supports device attention;
2 The platform can runtime power off the ODD through ACPI;
3 The ODD is either slot type or drawer type.
For such ODDs, zpodd_init is called and a new structure is allocated for
it to store ZPODD related stuffs.

And the zpodd_dev_enabled function is used to test if ZPODD is currently
enabled for this ODD.

A new config CONFIG_SATA_ZPODD is added to selectively build ZPODD code.

Signed-off-by: Aaron Lu <aaron.lu@intel.com>
libata: move acpi notification code to zpodd

Since the ata acpi notification code introduced in commit
3bd46600a7a7e938c54df8cdbac9910668c7dfb0 is solely for ZPODD, and we
now have a dedicated place for it, move these code there.

And the ata_acpi_add_pm_notifier code is changed a little bit in that it
is now invoked when scsi device is not bound with ACPI yet, so the way
to get the acpi handle is different with the previous version. And the
ata_acpi_add/remove_pm_notifier is also simplified a little bit in that
it doesn't check if the acpi_device for the handle exists or not as the
odd_can_poweroff function already checked that.

Signed-off-by: Aaron Lu <aaron.lu@intel.com>
libata: check zero power ready status for ZPODD

Per the Mount Fuji spec, the ODD is considered zero power ready when:
  - For slot type ODD, no media inside;
  - For tray type ODD, no media inside and tray closed.

The information can be retrieved by either the returned information of
command GET_EVENT_STATUS_NOTIFICATION(the command is used to poll for
media event) or sense code.

The information provided by the media status byte is not accurate, it
is possible that after a new disc is just inserted, the status byte
still returns media not present. So this information can not be used as
the deciding factor, we use sense code to decide if zpready status is
true.

When we first sensed the ODD in the zero power ready state, the
zp_sampled will be set and timestamp will be recoreded. And after ODD
stayed in this state for some pre-defined period, the ODD is considered
as power off ready and the zp_ready flag will be set. The zp_ready flag
serves as the deciding factor other code will use to see if power off is
OK for the ODD.

The Mount Fuji spec suggests a delay should be used here, to avoid the
case user ejects the ODD and then instantly inserts a new one again, so
that we can avoid a power transition. And some ODDs may be slow to place
its head to the home position after disc is ejected, so a delay here is
generally a good idea. And the delay time can be changed via the module
param zpodd_poweroff_delay.

The zero power ready status check is performed in the ata port's runtime
suspend code path, when port is not frozen yet, as we need to issue some
IOs to the ODD.

Signed-off-by: Aaron Lu <aaron.lu@intel.com>
libata: handle power transition of ODD

When ata port is runtime suspended, it will check if the ODD attched to
it is a zero power(ZP) capable ODD and if the ZP capable ODD is in zero
power ready state. And if this is not the case, the highest acpi state
will be limited to ACPI_STATE_D3_HOT to avoid powering off the ODD. And
if the ODD can be powered off, runtime wake capability needs to be
enabled and powered_off flag will be set to let resume code knows that
the ODD was in powered off state.

And on resume, before it is powered on, if it was powered off during
suspend, runtime wake capability needs to be disabled. After it is
recovered, the ODD is considered functional, post power on processing
like eject tray if the ODD is drawer type is done, and several ZPODD
related fields will also be reset.

Signed-off-by: Aaron Lu <aaron.lu@intel.com>
libata: expose pm qos flags for ata device

Expose pm qos flags to user space so that user has a chance to disable
ZPODD feature, if he/she has a broken platform or devices or simply does
not like this feature.

This flag is exposed to user space only for ZPODD devices.

Signed-off-by: Aaron Lu <aaron.lu@intel.com>
libata: scsi: no poll when ODD is powered off

When the ODD is powered off, any action the user did to the ODD that
would generate a media event will trigger an ACPI interrupt, so the
poll for media event is no longer necessary. And the poll will also
cause a runtime status change, which will stop the ODD from staying in
powered off state, so the poll should better be stopped.

But since we don't have access to the gendisk structure in LLDs, here
comes the disable_disk_events flag for scsi device. This flag serves as
a capability of the device, conveyed by the LLDs to upper layer. It is
set when LLDs know that this device will no longer generate any media
related events, so that the check_events can simply return 0 without
bothering the device, effectively silence the poll.

Signed-off-by: Aaron Lu <aaron.lu@intel.com>
libata: do not suspend port if normal ODD is attached

For ODDs, the upper layer will poll for media change every few
seconds, which will make it enter and leave suspend state very
often. And as each suspend will also cause a hard/soft reset,
the gain of runtime suspend is very little while the ODD may
malfunction after constantly being reset. So the idle callback
here will not proceed to suspend if a non-ZPODD capable ODD is
attached to the port.

Signed-off-by: Aaron Lu <aaron.lu@intel.com>
scsi: remove can_power_off flag from scsi_device

Commit 166a2967b45ede2e2e56f3ede3cd32053dc17812 "libata: tell scsi layer
device supports runtime power off" introduced the can_power_off flag for
scsi_device and is used to support ZPODD implementation in SCSI layer.
Since ZPODD is now implemented in ATA layer, that flag is no longer
needed, so remove it.

Signed-off-by: Aaron Lu <aaron.lu@intel.com>