Re: [PATCH v3 04/23] scsi: sd: Differentiate system and runtime start/stop management

[Hannes Reinecke <hare@suse.de>]

On 9/15/23 10:14, Damien Le Moal wrote:
> The underlying device and driver of a scsi disk may have different
> system and runtime power mode control requirements. This is because
> runtime power management affects only the scsi disk, while sustem level
> power management affects all devices, including the controller for the
> scsi disk.
> 
> For instance, issuing a START STOP UNIT command when a scsi disk is
> runtime suspended and resumed is fine: the command is translated to a
> STANDBY IMMEDIATE command to spin down the ATA disk and to a VERIFY
> command to wake it up. The scsi disk runtime operations have no effect
> on the ata port device used to connect the ATA disk. However, for
> system suspend/resume operations, the ATA port used to connect the
> device will also be suspended and resumed, with the resum operation
> requiring re-validating the device link and the device itseld. In this
> case, issuing a VERIFY command to spinup the disk must be done before
> starting to revalidate the device, when the ata port is being resumed.
> In such case, we must not allow the scsi disk driver to issue START STOP
> UNIT commands.
> 
> Allow a low level driver to refine the scsi disk start/stop management
> by differentiating system and runtime cases with two new scsi device
> flags: manage_system_start_stop and manage_runtime_start_stop. These new
> flags replace the current manage_start_stop flag. Drivers setting the
> manage_start_stop are modifed to set both new flags, thus preserving the
> existing start/stop management behavior.
> 
> Fixes: 0a8589055936 ("ata,scsi: do not issue START STOP UNIT on resume")
> Cc: stable@vger.kernel.org
> Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
> ---
>   drivers/ata/libata-scsi.c  |  3 +-
>   drivers/firewire/sbp2.c    |  9 +++--
>   drivers/scsi/sd.c          | 78 ++++++++++++++++++++++++++++----------
>   include/scsi/scsi_device.h |  3 +-
>   4 files changed, 69 insertions(+), 24 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		           Kernel Storage Architect
hare@suse.de			                  +49 911 74053 688
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