Hi, > From: Roger Quadros > Sent: Thursday, May 12, 2016 6:32 PM > > 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. Thank you for the reply. I understood it. > >>>> 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. R-Car Gen2 SoCs (r8a779[0134] / arm32) has USB 2.0 host controllers via PCI bus and one high speed function controller via AXI bus. One of channel can be used as host or function. > For DT case we could have a DT binding to tie the EHCI and companion and use that > in the OTG framework. R-Car Gen3 SoC (r8a7795 / arm64) will be this type. (Both USB 2.0 host/function controllers connect to AXI bus.) > Any objections? I don't have any objections because I'm just focus on R-Car Gen3 SoC for now. If someone needs for PCI case, I think it is possible to add such a code somehow later. Best regards, Yoshihiro Shimoda > 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
