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SubjectRe: [RFC] ata port runtime pm
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On Fri, 2011-10-28 at 11:37 +0800, Jeff Garzik wrote:
> On 10/27/2011 11:21 PM, Lin Ming wrote:
> > @@ -3208,6 +3209,11 @@ int ata_scsi_queuecmd(struct Scsi_Host *shost, struct scsi_cmnd *cmd)
> >
> > ap = ata_shost_to_port(shost);
> >
> > + if (pm_runtime_suspended(&ap->tdev))
> > + pm_runtime_resume(&ap->tdev);
> > + pm_runtime_mark_last_busy(&ap->tdev);
> > + pm_request_autosuspend(&ap->tdev);
> > +
> > spin_lock_irqsave(ap->lock, irq_flags);
> >
>
>
> Putting this into the core command dispatch fast-path is rather
> disappointing. That's at least one additional lock, plus some atomic
> instructions and tests.

Maybe move suspend request to the resume function, as below.

static int ata_port_runtime_resume(struct device *dev)
{
struct ata_port *ap = to_ata_port(dev);
int rc;
rc = ata_port_request_pm(ap, PMSG_ON, ATA_EH_RESET,
ATA_EHI_NO_AUTOPSY | ATA_EHI_QUIET, 1);
pm_runtime_mark_last_busy(dev);
pm_request_autosuspend(dev);

return rc;
}
Then the fast-path looks like,

@@ -3208,6 +3209,9 @@ int ata_scsi_queuecmd(struct Scsi_Host *shost,
struct scsi_cmnd *cmd)

ap = ata_shost_to_port(shost);

+ if (pm_runtime_suspended(&ap->tdev))
+ pm_runtime_resume(&ap->tdev);
+
spin_lock_irqsave(ap->lock, irq_flags);
ata_scsi_dump_cdb(ap, cmd);

What do you think?

Thanks,
Lin Ming



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