В Fri, 29 Aug 2008 11:26:07 -0400 (EDT)
Alan Stern [off-list ref] пишет:

On Fri, 29 Aug 2008, Benjamin Herrenschmidt wrote:

quoted

I suppose some embedded platforms don't use CONFIG_PM, is this
still a requirement for autosuspend ? Or do that happen always on
an empty port nowadays ?

ohci-hcd doesn't automatically suspend the root hub if CONFIG_PM isn't
set.  However it isn't necessary to set CONFIG_SLEEP,
CONFIG_HIBERNATION, or CONFIG_USB_SUSPEND.

That is good to know. 

But even assuming PM set, common use-case of
embedded systems to have stuff on USB bus that is never plugged off;
and in case of compiled-in ehci and ohci there is just 

Initializing USB Mass Storage driver...
usb 1-1: new high speed USB device using ppc-of-ehci and address 2
usb 1-1: device descriptor read/all, error -110
hub 1-0:1.0: unable to enumerate USB device on port 1

(not touching PM here to be clear)

even 1-second delay would be enough for root hub to be hosed... So, is
the patch (with all the issues addressed) acceptable for mainline?

Thanks, 
-Vitaly