Re: [GIT PULL] PM updates for 2.6.33

Alan Stern
2009-12-07T22:21:31Z

On Mon, 7 Dec 2009, Linus Torvalds wrote:

> I also suspect that even if you do the USB host controller suspend
> synchronously, doing the actual USB devices asynchronously would still
> help - even if it's only "asynchronously per bus" thing.
>
> So in fact, it's probably a good first step to start off doing only the
> USB devices, not the controller.

Interesting you should say that. The patch I asked Arjan to test
involved not suspending USB devices at all (root hubs being the
exception). That is in fact just what we do when CONFIG_USB_SUSPEND
isn't set.

There's no need to suspend the individual devices when the whole system
is going down. They will automatically suspend when the controller
stops sending out SOF packets, which occurs when the root hub is
suspended. The USB spec describes this, grandiosely, as a "global
suspend".

But yes, I agree. Doing just the USB devices is a good first step.

Alan Stern