Hi, On 12/05/16 11:34, Roger Quadros wrote: > On 12/05/16 07:00, Yoshihiro Shimoda wrote: >> Hi, >> >>> From: Alan Stern >>> Sent: Wednesday, May 11, 2016 11:47 PM >>> >>> On Wed, 11 May 2016, Roger Quadros wrote: >>> >>>>> What I mean is if you have 2 EHCI controllers with 2 companion >>>>> controllers, don't you need to know which companion goes with which EHCI >>>>> controller? Just like you do for the otg-controller property. >>>>> >>>> >>>> That is a very good point. I'm not very sure and it seems that current code won't work >>>> with multiple EHCI + companion instances. >> >> I may misunderstand this topic, but if I use the following environment, it works correctly. >> >> < My environment > >> - an otg controller: Sets hcd-needs-companion. >> - ehci0 and ohci0 and a function: They connect to the otg controller using "otg-controller" property. >> - ehci1 and ohci1: No "otg-controller" property. >> - ehci2 and ohci2: No "otg-controller" property. >> >> In this environment, all hosts works correctly. >> Also I think if we have 2 otg controlelrs, it should be work because otg_dev instance differs. > > The topic is about more than one otg controllers and how to tie the right ehci and ohci > to the correct otg_dev instance especially in cases where we can't depend on probe order. > >> Or, does this topic assume an otg controller handles 2 EHCI controllers? >> I'm not sure such environment actually exists. > > No it is not about that. > >> >>>> Alan, does USB core even know which EHCI and OHCI are linked to the same port >>>> or the handoff is software transparent? >>> >>> The core knows. It doesn't use the information for a whole lot of >>> things, but it does use it in a couple of places. Search for >>> "companion" in core/hcd-pci.c and you'll see. >> >> Thank you for the information. I didn't know this code. >> If my understanding is correct, the core/hcd-pci.c code will not be used by non-PCI devices. > > That is correct. > >> In other words, nobody sets "hcd->self.hs_companion" if we use such a device. >> So, I will try to add such a code if needed. > > I think OTG core would have to rely on USB core in providing the right companion device, > just like we rely on it for the primary vs shared HCD case. > OK, it is not so simple. EHCI and companion port handoff is really meant to be software transparent. non-PCI devices really don't have knowledge of which OHCI instance is companion to the EHCI. With device tree we could provide this mapping but for non-device tree case we can't do anything. So my suggestion would be to keep dual role implementation limited to one instance for EHCI + companion case for non-DT. For PCI case I don't see how dual role can be implemented. I don't think we have any dual-role PCI cards. For DT case we could have a DT binding to tie the EHCI and companion and use that in the OTG framework. Any objections? cheers, -roger -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
