On 16/05/16 11:13, Peter Chen wrote: > 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. > I'm sorry for the confusion. What I meant by "we don't need this special binding" was that we don't need additional binding to link the HCD and companion HCD. 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
