On Mon, Sep 11, 2023 at 01:02:02PM +0900, Damien Le Moal wrote:
> The introduction of a device link to create a consumer/supplier
> relationship between the scsi device of an ATA device and the ATA port
> of the ATA device fixed the ordering of the suspend and resume
> operations. For suspend, the scsi device is suspended first and the ata
> port after it. This is fine as this allows the synchronize cache and
> START STOP UNIT commands issued by the scsi disk driver to be executed
> before the ata port is disabled.
>
> For resume operations, the ata port is resumed first, followed
> by the scsi device. This allows having the request queue of the scsi
> device to be unfrozen after the ata port restart is scheduled in EH,
> thus avoiding to see new requests issued to the ATA device prematurely.
> However, since libata sets manage_start_stop to 1, the scsi disk resume
> operation also results in issuing a START STOP UNIT command to wakeup
> the device. This is too late and that must be done before libata EH
> resume handling starts revalidating the drive with IDENTIFY etc
> commands. Commit 0a8589055936 ("ata,scsi: do not issue START STOP UNIT
> on resume") disabled issuing the START STOP UNIT command to avoid
> issues with it. However, this is incorrect as transitioning a device to
> the active power mode from the standby power mode set on suspend
> requires a media access command. The device link reset and subsequent
> SET FEATURES, IDENTIFY and READ LOG commands executed in libata EH
> context triggered by the ata port resume operation may thus fail.
>
> Fix this by handling a device power mode transitions for suspend and
> resume in libata EH context without relying on the scsi disk management
> triggered with the manage_start_stop flag.
>
> To do this, the following libata helper functions are introduced:
>
> 1) ata_dev_power_set_standby():
>
> This function issues a STANDBY IMMEDIATE command to transitiom a device
> to the standby power mode. For HDDs, this spins down the disks. This
> function applies only to ATA and ZAC devices and does nothing otherwise.
> This function also does nothing for devices that have the
> ATA_FLAG_NO_POWEROFF_SPINDOWN or ATA_FLAG_NO_HIBERNATE_SPINDOWN flag
> set.
>
> For suspend, call ata_dev_power_set_standby() in
> ata_eh_handle_port_suspend() before the port is disabled and frozen.
> ata_eh_unload() is also modified to transition all enabled devices to
> the standby power mode when the system is shutdown or devices removed.
>
> 2) ata_dev_power_set_active() and
>
> This function applies to ATA or ZAC devices and issues a VERIFY command
> for 1 sector at LBA 0 to transition the device to the active power mode.
> For HDDs, since this function will complete only once the disk spin up.
> Its execution uses the same timeouts as for reset, to give the drive
> enough time to complete spinup without triggering a command timeout.
>
> For resume, call ata_dev_power_set_active() in
> ata_eh_revalidate_and_attach() after the port has been enabled and
> before any other command is issued to the device.
>
> With these changes, the manage_start_stop flag does not need to be set
> in ata_scsi_dev_config().
>
> Fixes: 0a8589055936 ("ata,scsi: do not issue START STOP UNIT on resume")
> Fixes: a19a93e4c6a9 ("scsi: core: pm: Rely on the device driver core for async power management")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Damien Le Moal <dlemoal@xxxxxxxxxx>
Tested-by: Chia-Lin Kao (AceLan) <acelan.kao@xxxxxxxxxxxxx>
