Re: REQ_PM vs REQ_TYPE_PM_RESUME

[Aaron Lu <aaron.lu@intel.com>]

On 01/08/2014 09:16 AM, Phillip Susi wrote:
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> On 01/07/2014 08:03 PM, Aaron Lu wrote:
>> You mean you want to leave the disk runtime suspended after a
>> system resume and in the meantime make sure the disk is indeed not
>> spun up?
> 
> Yep.  If it is spun up, then the runtime status should be updated to
> reflect that, otherwise it tricks user space programs into avoiding
> doing IO to the disk for fear of waking it, and prevents the runtime
> autosuspend timer from kicking in.

The ATA and SCSI devices are all resumed in my patches, notice there is
a single pm_request_resume call in both ATA and SCSI's system resume
callback, so the runtime status and the disk's state is synced.
The pm_request_resume call is asynchronous to the system resume, so it
doesn't block system resume.

But I see your point, my patch will not achieve that, it can only speed
up S3 for a typical PC with a traditional disk. I can omit the
pm_request_resume call in the system resume callback, but then if the
disk is spun up by itself, then the runtime status indeed doesn't
reflect the actual state. I suppose for SATA controllers that support
Staggered Spin-up wouldn't do this?