On Thu, May 12, 2016 at 03:13:48PM +0300, Roger Quadros wrote: > Hi, > > On 12/05/16 13:31, Yoshihiro Shimoda wrote: > > 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. > > After looking at the code it seems we don't need this special binding as we are already > linking the EHCI controller and companion controller to the single otg controller instance > using the otg-controller property. > Then, how you know this EHCI + companion controller special case during otg adds hcd, it needs special handling, right? Peter > So all is good as of now. > > For non DT case, it is the responsibility of platform support code to ensure that > it calls usb_otg_add_hcd() with the correct otg controller instance for both EHCI and > companion controller and things should work fine there as well. > > -- > cheers, > -roger > > > > > 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-usb" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Best Regards, Peter Chen -- 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
