On Wed, Aug 13, 2014 at 09:41:17PM +0000, Paul Zimmerman wrote: > > From: Alan Stern [mailto:stern@xxxxxxxxxxxxxxxxxxx] > > Sent: Wednesday, August 13, 2014 2:09 PM > > > > On Wed, 13 Aug 2014, Paul Zimmerman wrote: > > > > > > > Is there a difference between a VBus on/off and a connect/disconnect? > > > > > Because AFAIK the Synopsys USB 3.0 controller (unless it is configured > > > > > for OTG mode) does not have a way to detect when VBus is enabled/ > > > > > disabled, other than by a connect/disconnect interrupt. > > > > > > > > That's an excellent point; it completely slipped my mind. So we > > > > already have all the callbacks we need. > > > > > > No, that was a brain fart on my part. The DWC3 controller needs to have > > > the pullups enabled before it can see a connect. Well, it's actually > > > the host that won't see the device being connected until the pullups > > > are enabled, but it amounts to the same thing, since the device needs > > > to see some bus activity from the host before it asserts the ConnectDone > > > interrupt. > > > > Then how can the DWC3 be USB-compliant? It can't see a connect unless > > the pullups are enabled, but enabling the pullups before Vbus is active > > violates the USB spec. > > > > Does the controller hardware have some special switch that prevents the > > pullup from engaging if Vbus is off? > > Either in the controller or in the Synopsys Phy, I'm not sure which. It > seems like an obvious thing to be handled automatically by the hardware. > > We've never seen a failure on the USB-IF test suite as was mentioned > earlier in the thread, and we have our device hardware recertified on > a regular basis. using a mainline linux kernel or something entirely different ? It could be that this would only be apparent with a recent linux gadget framework. cheers -- balbi
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