[PATCH 1/2] gpio-vbus: support disabling D+ pullup on suspend

[Alan Stern]

On Wed, 22 Jun 2011, Felipe Balbi wrote:

> Hi,
> 
> On Wed, Jun 22, 2011 at 04:20:16PM +0400, Dmitry Eremin-Solenikov wrote:
> > Some platforms would like to disable D+ pullup on suspend, to drain as
> > low power, as possible. E.g. this was requested by mioa701 board
> > maintainers.
> 
> I think this makes sense to many platforms, but by doing so, you would
> loose connection to the Host PC, so you need to make sure your device
> isn't been used before you go down this road.

In fact, something like this is _necessary_ for all UDC/PHY drivers
unless the device can guarantee that it will automatically wake up from
suspend in time to service a USB packet (note that the window for
responding to a packet is only a few microseconds).  Otherwise the
device would appear to the host to be unresponsive and broken -- better
to do a clean disconnect.

If suspending the device while it is in use would cause problems ...  
then don't suspend it when it is in use!

Alan Stern