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    SubjectRe: [PATCH 0/6] twl4030: Various fixes for charing-from-USB
    On Thu, 10 May 2012, NeilBrown wrote:

    > Maybe we need to not suspend the USB OTG interface when the device as a
    > whole enters suspend-to-RAM. Maybe we need to register a dummy gadget to
    > the bus active while in suspend?
    > Does the gadget have to be responsive while-ever the bus is not suspended?

    Yes.

    > Maybe we can arrange for any USB activity to trigger a resume?

    Probably not, at least, not fast enough. The gadget is required to
    respond to USB packets within a few microseconds. At a minimum, the
    USB device controller would have to remain fully powered.

    > Entering suspend while still charging really should be possible - at least
    > with a dump charger and hopefully from a host port as well. I'll like to
    > find the best way to achieve that, and any help you can provide would be
    > greatly appreciated.

    If the gadget is attached to a dumb charger rather than a host then
    there's no problem. But otherwise it's not so simple.

    Have you read the USB charger class specification? (I haven't...)

    Alan Stern



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