On Fri, 6 Aug 2010, Wu, Hao wrote: > >> From: Hao Wu <hao.wu@xxxxxxxxx> > >> > >> Update PCI suspend/resume function to fix suspend/resume issue. This > >> modification will make sure in D3, Vbus is powered off, both client/host > >> function will be stopped and controller moves to OTG IDLE state. Once it > >> resumes back to work, state machine will restart from the IDLE state, and move > >> to host/client based on inputs event. > > > >Even though this patch isn't present in the revised patch series, I > >still wanted to ask a question about it. Why should Vbus be powered > >off in D3? Isn't the bus supposed to remain powered while everything > >is suspended? Otherwise how can you detect plug/unplug events? > > > > Really thanks for patch review. : ) > > The actual purpose is to save power as much as possible for Intel MID platform. > And OTG devices should turn off the Vbus when user doesn't want to use the USB > bus to save power per OTG State machine in Spec, D3 is the same case. So VBus > is powered off in D3. > > In D3, although Vbus is off and its OTG state is in IDLE, other OTG events are all > available. It can detect cable remove/connect via id changes and detect VBus > changes as well. Okay. Thanks for the explanation. 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
