On Wed, Jun 22, 2016 at 09:56:22AM +0300, Felipe Balbi wrote: > > Hi, > > Peter Chen <hzpeterchen@xxxxxxxxx> writes: > >> Peter Chen <hzpeterchen@xxxxxxxxx> writes: > >> >> >> So far, I haven't seen anybody talking about real USB OTG (the spec) > >> >> >> when they say OTG. Usually they just mean "a method for swapping between > >> >> >> host and peripheral roles, but we really don't want all the extra cost > >> >> >> of the OTG specification". > >> >> >> > >> >> > > >> >> > That's what I thought before, but the request from the Marketing guy is > >> >> > "To prove the SoC is OTG compliance, support HNP and SRP", don't you > >> >> > see the SoC reference manual say "it supports HNP and SRP"? > >> >> > > >> >> > If there is no request, who else wants to implement so complicated FSM > >> >> > but seldom use cases, and go to pass OTG compliance test (tested by PET). > >> >> > >> >> I stand corrected :-) > >> >> > >> >> So there is one user for this layer. And this user has its own role > >> >> control registers. I'm not convinced we need this large generic layer > >> >> for one user. > >> >> > >> > > >> > You mean chipidea or dwc3? I have more comments below. > >> > >> chipidea. From the point of OTG (or DRD) dwc3 is very > >> self-sufficient. HW itself tracks state machine, much like MUSB does. > > > > You mean HW can do state machine switch? If we are A device, > > - Does the hardware knows if B device is HNP enabled or not? > > that's enabled through control message, keep a flag. > > > - And if B device is HNP enabled, does it can switch itself from host > > to peripheral when the B device is disconnected (a_suspend->a_peripheral) > > It cannot. It must rely on hnp polling which is, again, a control message. > > > Does hardware can really follow Figure 7-1: OTG A-device with HNP State > > Diagram at On-The-Go and Embedded Host Supplement to the USB Revision > > 2.0 Specification? And can pass PET test? > > Seriously, what does this add to the conversation? It has already been > stated that there's nobody asking for OTG certification on dwc3. So all > of this is vaporware from the point of view of dwc3. This is just a technical question that I can't understand your words "HW itself tracks state machine"? -- Best Regards, Peter Chen -- 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
