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. cheers, -roger > > 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 > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
