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:
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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