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> Signed-off-by:
Jeff Garzik <jgarzik@redhat.com>
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