RE: [PATCH v7 10/14] usb: otg: add hcd companion support

From	Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Newsgroups	linux.kernel
Subject	RE: [PATCH v7 10/14] usb: otg: add hcd companion support
Date	2016-05-12 12:40 +0200
Message-ID	<rxWca-3K2-23@gated-at.bofh.it> (permalink)
References	<rxD9w-1n1-21@gated-at.bofh.it> <rxDCy-1G3-9@gated-at.bofh.it> <rxQ6J-68P-1@gated-at.bofh.it> <rxUk2-1QS-5@gated-at.bofh.it> <rxVg7-2MC-15@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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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

Thread

[PATCH v7 00/14] USB OTG/dual-role framework Roger Quadros <rogerq@ti.com> - 2016-05-02 14:20 +0200
  [PATCH v7 02/14] usb: otg-fsm: Prevent build warning "VDBG" redefined Roger Quadros <rogerq@ti.com> - 2016-05-02 14:20 +0200
    Re: [PATCH v7 02/14] usb: otg-fsm: Prevent build warning "VDBG"  redefined Peter Chen <hzpeterchen@gmail.com> - 2016-05-11 10:30 +0200
  [PATCH v7 07/14] usb: otg: get rid of CONFIG_USB_OTG_FSM in favour of CONFIG_USB_OTG Roger Quadros <rogerq@ti.com> - 2016-05-02 14:30 +0200
    Re: [PATCH v7 07/14] usb: otg: get rid of CONFIG_USB_OTG_FSM in  favour of CONFIG_USB_OTG Peter Chen <hzpeterchen@gmail.com> - 2016-05-11 10:40 +0200
  [PATCH v7 09/14] usb: of: add an API to get OTG device from USB controller node Roger Quadros <rogerq@ti.com> - 2016-05-02 14:30 +0200
    Re: [PATCH v7 09/14] usb: of: add an API to get OTG device from USB  controller node Rob Herring <robh@kernel.org> - 2016-05-04 15:20 +0200
    Re: [PATCH v7 09/14] usb: of: add an API to get OTG device from USB  controller node Peter Chen <hzpeterchen@gmail.com> - 2016-05-11 10:50 +0200
      Re: [PATCH v7 09/14] usb: of: add an API to get OTG device from USB  controller node Roger Quadros <rogerq@ti.com> - 2016-05-11 13:10 +0200
  [PATCH v7 11/14] usb: otg: use dev_dbg() instead of VDBG() Roger Quadros <rogerq@ti.com> - 2016-05-02 14:30 +0200
    Re: [PATCH v7 11/14] usb: otg: use dev_dbg() instead of VDBG() Peter Chen <hzpeterchen@gmail.com> - 2016-05-06 11:20 +0200
      Re: [PATCH v7 11/14] usb: otg: use dev_dbg() instead of VDBG() Roger Quadros <rogerq@ti.com> - 2016-05-09 11:50 +0200
        Re: [PATCH v7 11/14] usb: otg: use dev_dbg() instead of VDBG() Peter Chen <hzpeterchen@gmail.com> - 2016-05-11 11:00 +0200
  [PATCH v7 14/14] usb: host: xhci-plat: Add otg device to platform data Roger Quadros <rogerq@ti.com> - 2016-05-02 14:30 +0200
    Re: [PATCH v7 14/14] usb: host: xhci-plat: Add otg device to  platform data Peter Chen <hzpeterchen@gmail.com> - 2016-05-11 11:10 +0200
  [PATCH v7 03/14] usb: hcd.h: Add OTG to HCD interface Roger Quadros <rogerq@ti.com> - 2016-05-02 14:30 +0200
    Re: [PATCH v7 03/14] usb: hcd.h: Add OTG to HCD interface Peter Chen <hzpeterchen@gmail.com> - 2016-05-06 11:50 +0200
      Re: [PATCH v7 03/14] usb: hcd.h: Add OTG to HCD interface Roger Quadros <rogerq@ti.com> - 2016-05-09 11:50 +0200
        Re: [PATCH v7 03/14] usb: hcd.h: Add OTG to HCD interface Peter Chen <hzpeterchen@gmail.com> - 2016-05-10 05:30 +0200
          Re: [PATCH v7 03/14] usb: hcd.h: Add OTG to HCD interface Roger Quadros <rogerq@ti.com> - 2016-05-10 09:40 +0200
            Re: [PATCH v7 03/14] usb: hcd.h: Add OTG to HCD interface Felipe Balbi <balbi@kernel.org> - 2016-05-10 10:20 +0200
              Re: [PATCH v7 03/14] usb: hcd.h: Add OTG to HCD interface Roger Quadros <rogerq@ti.com> - 2016-05-10 11:20 +0200
            RE: [PATCH v7 03/14] usb: hcd.h: Add OTG to HCD interface Jun Li <jun.li@nxp.com> - 2016-05-10 10:20 +0200
              Re: [PATCH v7 03/14] usb: hcd.h: Add OTG to HCD interface Roger Quadros <rogerq@ti.com> - 2016-05-10 11:30 +0200
                Re: [PATCH v7 03/14] usb: hcd.h: Add OTG to HCD interface Peter Chen <hzpeterchen@gmail.com> - 2016-05-11 08:30 +0200
  [PATCH v7 12/14] usb: hcd: Adapt to OTG core Roger Quadros <rogerq@ti.com> - 2016-05-02 14:30 +0200
    Re: [PATCH v7 12/14] usb: hcd: Adapt to OTG core Peter Chen <hzpeterchen@gmail.com> - 2016-05-11 11:10 +0200
  [PATCH v7 01/14] usb: hcd: Initialize hcd->flags to 0 Roger Quadros <rogerq@ti.com> - 2016-05-02 14:30 +0200
    Re: [PATCH v7 01/14] usb: hcd: Initialize hcd->flags to 0 Peter Chen <hzpeterchen@gmail.com> - 2016-05-06 11:20 +0200
  [PATCH v7 06/14] usb: gadget.h: Add OTG to gadget interface Roger Quadros <rogerq@ti.com> - 2016-05-02 14:30 +0200
  [PATCH v7 08/14] usb: otg: add OTG/dual-role core Roger Quadros <rogerq@ti.com> - 2016-05-02 14:30 +0200
    Re: [PATCH v7 08/14] usb: otg: add OTG/dual-role core Peter Chen <hzpeterchen@gmail.com> - 2016-05-11 10:50 +0200
      Re: [PATCH v7 08/14] usb: otg: add OTG/dual-role core Roger Quadros <rogerq@ti.com> - 2016-05-11 13:10 +0200
  [PATCH v7 13/14] usb: gadget: udc: adapt to OTG core Roger Quadros <rogerq@ti.com> - 2016-05-02 14:30 +0200
  [PATCH v7 05/14] usb: otg-fsm: move host controller operations into usb_otg->hcd_ops Roger Quadros <rogerq@ti.com> - 2016-05-02 14:30 +0200
    Re: [PATCH v7 05/14] usb: otg-fsm: move host controller operations  into usb_otg->hcd_ops Peter Chen <hzpeterchen@gmail.com> - 2016-05-11 08:20 +0200
      Re: [PATCH v7 05/14] usb: otg-fsm: move host controller operations  into usb_otg->hcd_ops Roger Quadros <rogerq@ti.com> - 2016-05-11 13:10 +0200
        Re: [PATCH v7 05/14] usb: otg-fsm: move host controller operations  into usb_otg->hcd_ops Roger Quadros <rogerq@ti.com> - 2016-05-11 14:40 +0200
          Re: [PATCH v7 05/14] usb: otg-fsm: move host controller operations  into usb_otg->hcd_ops Peter Chen <hzpeterchen@gmail.com> - 2016-05-12 10:30 +0200
            Re: [PATCH v7 05/14] usb: otg-fsm: move host controller operations  into usb_otg->hcd_ops Roger Quadros <rogerq@ti.com> - 2016-05-12 10:40 +0200
  [PATCH v7 10/14] usb: otg: add hcd companion support Roger Quadros <rogerq@ti.com> - 2016-05-02 14:30 +0200
    Re: [PATCH v7 10/14] usb: otg: add hcd companion support Rob Herring <robh@kernel.org> - 2016-05-04 15:20 +0200
      Re: [PATCH v7 10/14] usb: otg: add hcd companion support Roger Quadros <rogerq@ti.com> - 2016-05-04 15:50 +0200
        Re: [PATCH v7 10/14] usb: otg: add hcd companion support Rob Herring <robh@kernel.org> - 2016-05-11 16:00 +0200
          Re: [PATCH v7 10/14] usb: otg: add hcd companion support Roger Quadros <rogerq@ti.com> - 2016-05-11 16:20 +0200
            Re: [PATCH v7 10/14] usb: otg: add hcd companion support Alan Stern <stern@rowland.harvard.edu> - 2016-05-11 16:50 +0200
              RE: [PATCH v7 10/14] usb: otg: add hcd companion support Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com> - 2016-05-12 06:10 +0200
                Re: [PATCH v7 10/14] usb: otg: add hcd companion support Roger Quadros <rogerq@ti.com> - 2016-05-12 10:40 +0200
                Re: [PATCH v7 10/14] usb: otg: add hcd companion support Roger Quadros <rogerq@ti.com> - 2016-05-12 11:40 +0200
                RE: [PATCH v7 10/14] usb: otg: add hcd companion support Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com> - 2016-05-12 12:40 +0200
                Re: [PATCH v7 10/14] usb: otg: add hcd companion support Roger Quadros <rogerq@ti.com> - 2016-05-12 14:20 +0200
                Re: [PATCH v7 10/14] usb: otg: add hcd companion support Peter Chen <hzpeterchen@gmail.com> - 2016-05-16 04:30 +0200
                Re: [PATCH v7 10/14] usb: otg: add hcd companion support Roger Quadros <rogerq@ti.com> - 2016-05-16 10:10 +0200
                Re: [PATCH v7 10/14] usb: otg: add hcd companion support Peter Chen <hzpeterchen@gmail.com> - 2016-05-16 10:30 +0200
                Re: [PATCH v7 10/14] usb: otg: add hcd companion support Roger Quadros <rogerq@ti.com> - 2016-05-16 10:40 +0200
                RE: [PATCH v7 10/14] usb: otg: add hcd companion support Alan Stern <stern@rowland.harvard.edu> - 2016-05-12 20:20 +0200
    Re: [PATCH v7 10/14] usb: otg: add hcd companion support Peter Chen <hzpeterchen@gmail.com> - 2016-05-11 11:00 +0200
  Re: [PATCH v7 00/14] USB OTG/dual-role framework Peter Chen <hzpeterchen@gmail.com> - 2016-05-11 10:50 +0200
    Re: [PATCH v7 00/14] USB OTG/dual-role framework Roger Quadros <rogerq@ti.com> - 2016-05-11 13:10 +0200

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