Messages in this thread | | | Date | Thu, 10 May 2012 10:45:50 -0400 (EDT) | From | Alan Stern <> | Subject | Re: [PATCH 0/6] twl4030: Various fixes for charing-from-USB |
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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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