On Wed, 2011-11-16 at 00:08 +0800, Alan Stern wrote:
> On Tue, 15 Nov 2011, Tejun Heo wrote:
>
> > On Tue, Nov 15, 2011 at 04:51:29PM +0800, Lin Ming wrote:
> > > > This is not the right approach. You should look instead at
> > > > scsi_dev_type_suspend() in scsi_pm.c. If the device is already runtime
> > > > suspended then the routine should return immediately.
> > >
> > > How about below?
> > >
> > > diff --git a/drivers/scsi/scsi_pm.c b/drivers/scsi/scsi_pm.c
> > > index d329f8b..94b60bd 100644
> > > --- a/drivers/scsi/scsi_pm.c
> > > +++ b/drivers/scsi/scsi_pm.c
> > > @@ -20,6 +20,9 @@ static int scsi_dev_type_suspend(struct device *dev, pm_message_t msg)
> > > struct device_driver *drv;
> > > int err;
> > >
> > > + if (pm_runtime_suspended(dev))
> > > + return 0;
> > > +
> >
> > Something to be careful about is there are different types of suspend
> > states (PMSG_*). IIUC, runtime PM is using PMSG_SUSPEND. Other
> > states may or may not be compatible with PMSG_SUSPEND expectations, so
> > you can skip suspend operation if the newly requested state is
> > PMSG_SUSPEND but otherwise the controller needs to be woken up and
> > told to comply to the new state.
>
> That's right. Surprisingly enough (and contrary to what I wrote
> earlier), the sd_suspend() routine doesn't spin down a drive for
> runtime suspend. This probably should be considered a bug.
>
> Anyway, it looks like the correct approach would be more like this:
Thanks.
I think ata_port_suspend also needs to call pm_runtime_resume, as below.
static int ata_port_suspend(struct device *dev)
{
struct ata_port *ap = to_ata_port(dev);
int rc;
pm_runtime_resume(dev);
rc = ata_port_request_pm(ap, PMSG_SUSPEND, 0, ATA_EHI_QUIET, 1);
return rc;
}
>
> static int scsi_bus_suspend_common(struct device *dev, pm_message_t msg)
> {
> int err = 0;
>
> - if (scsi_is_sdev_device(dev))
> + if (scsi_is_sdev_device(dev)) {
> pm_runtime_resume(dev);
> err = scsi_dev_type_suspend(dev, msg);
> + }
> return err;
> }
>
> Alan Stern
>
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