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SubjectRe: [RFC] ata port runtime pm
Date
Please CC PM-related patches to linux-pm@vger.kernel.org (now added).

Thanks,
Rafael


On Friday, October 28, 2011, Lin Ming wrote:
> 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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