On Mon, May 16, 2016 at 11:01:27AM +0300, Roger Quadros wrote: > On 16/05/16 05:13, Peter Chen wrote: > > 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? > > We know the special case by using the hcd_needs_companion flag. > You had said "we don't need this..", ok, yes, we do need it. -- Best Regards, Peter Chen -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
