On Tue, 7 Jan 2014, Phillip Susi wrote:
> On 1/7/2014 10:25 AM, Alan Stern wrote:
> > This doesn't seem like a good idea. The way to speed up resumes is
> > to allow sd's resume routine to return while the disk is still
> > spinning up (i.e., make the spin-up asynchronous). There already
> > have been patches submitted to do this; I don't know what happened
> > to them.
>
> Sure, if that is your *only* goal. I also want the disk to not spin
> up *at all* if possible. There's no sense spinning up all of your
> disks every time you resume when you very rarely access some of them.
Okay, that's a different matter. There's a much simpler way to
accomplish this. The patch below will avoid spinning up drives that
were already in runtime suspend when the system sleep started.
(If a drive wasn't in runtime suspend then presumably it was used
recently; therefore it's likely to be used again in the near future and
so it _should_ be spun up.)
Warning: This patch is completely untested. I didn't even try to
compile it. Still, it should give you a good idea as to what is really
needed here.
Alan Stern
Index: usb-3.13/drivers/scsi/scsi_pm.c
===================================================================
--- usb-3.13.orig/drivers/scsi/scsi_pm.c
+++ usb-3.13/drivers/scsi/scsi_pm.c
@@ -71,14 +71,11 @@ scsi_bus_resume_common(struct device *de
{
int err = 0;
+ if (pm_runtime_status_suspended(dev))
+ return err;
+
if (scsi_is_sdev_device(dev))
err = scsi_dev_type_resume(dev, cb);
-
- if (err == 0) {
- pm_runtime_disable(dev);
- pm_runtime_set_active(dev);
- pm_runtime_enable(dev);
- }
return err;
}
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