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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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