On Tue, 16 Oct 2012, Alan Stern wrote: > On Tue, 16 Oct 2012, Sarah Sharp wrote: > > > > The kernel support we have now for USB-2 LPM doesn't make any sense. > > > usb_port_suspend() disables LPM before changing the link state out of > > > L0, and usb_port_resume() enables LPM after changing the state back to > > > L0. > > > > > > Thus LPM is disabled precisely at the times when it might be useful! > > > > One thing to understand is that the USB 2.1 LPM code is designed to only > > take advantage of host controllers that can do hardware-controlled LPM. > > Not so. At least, not in the two documents that are part of the USB-2 > zip archive currently available from www.usb.org. They make no > mention of automatic power-level changes; everything has to be > initiated by the host OS (except for device-initiated wakeup). Oh, I just re-read what you wrote. Although the LPM _spec_ makes no mention of hardware-controlled LPM, your point is that the _code_ in hub.c is meant for it. Okay, now I got it. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
