From: Peter Chen <hzpeterchen@gmail.com>
To: Felipe Balbi <balbi@kernel.org>
Cc: Roger Quadros <rogerq@ti.com>,
peter.chen@freescale.com, tony@atomide.com,
gregkh@linuxfoundation.org, dan.j.williams@intel.com,
mathias.nyman@linux.intel.com, Joao.Pinto@synopsys.com,
sergei.shtylyov@cogentembedded.com, jun.li@freescale.com,
grygorii.strashko@ti.com, yoshihiro.shimoda.uh@renesas.com,
robh@kernel.org, nsekhar@ti.com, b-liu@ti.com, joe@perches.com,
linux-usb@vger.kernel.org, linux-omap@vger.kernel.org,
linux-kernel@vger.kernel.org, devicetree@vger.kernel.org
Subject: Re: [PATCH v11 08/14] usb: otg: add OTG/dual-role core
Date: Tue, 21 Jun 2016 17:07:38 +0800 [thread overview]
Message-ID: <20160621090738.GD5108@shlinux2> (raw)
In-Reply-To: <877fdjovef.fsf@linux.intel.com>
On Tue, Jun 21, 2016 at 10:26:00AM +0300, Felipe Balbi wrote:
>
> Hi,
>
> >>
> >> So far, I haven't seen anybody talking about real USB OTG (the spec)
> >> when they say OTG. Usually they just mean "a method for swapping between
> >> host and peripheral roles, but we really don't want all the extra cost
> >> of the OTG specification".
> >>
> >
> > That's what I thought before, but the request from the Marketing guy is
> > "To prove the SoC is OTG compliance, support HNP and SRP", don't you
> > see the SoC reference manual say "it supports HNP and SRP"?
> >
> > If there is no request, who else wants to implement so complicated FSM
> > but seldom use cases, and go to pass OTG compliance test (tested by PET).
>
> I stand corrected :-)
>
> So there is one user for this layer. And this user has its own role
> control registers. I'm not convinced we need this large generic layer
> for one user.
>
You mean chipidea or dwc3? I have more comments below.
> >> > For the real use case, some Carplay platforms need it.
> >>
> >> Carplay does *NOT* rely on OTG. Apple has its own proprietary and closed
> >> specification which is not OTG-compliant.
> >>
> >
> > Yes, it is not OTG-compliant, but it can co-work with some standard OTG FSM
> > states to finish role swap.
>
> What are you referring to as "finish role swap"? I don't get that.
Change current role from host to peripheral.
>
> > Notice, it needs to swap role without disconnect cable.
>
> right, I can swap role without changing cable, but that's not OTG. The
> mechanism for that, AFAICT, is not HNP. I don't know details about
> CarPlay because the spec isn't public, but my understanding is that
> CarPlay doesn't rely on anything from OTG spec.
Since it is non-public, I can't say much. Some flows of its role-swap
refers to On-The-Go and Embedded Host Supplement to the USB Revision 2.0
Specification.
But OTG FSM is not the only way, the platform which can do role-swap
without disconnection can support it too.
>
> >> >> > diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
> >> >> > index f4fc0aa..1d74fb8 100644
> >> >> > --- a/include/linux/usb/gadget.h
> >> >> > +++ b/include/linux/usb/gadget.h
> >> >> > @@ -328,6 +328,7 @@ struct usb_gadget_ops {
> >> >> > * @in_epnum: last used in ep number
> >> >> > * @mA: last set mA value
> >> >> > * @otg_caps: OTG capabilities of this gadget.
> >> >> > + * @otg_dev: OTG controller device, if needs to be used with OTG core.
> >> >>
> >> >> do you really know of any platform which has a separate OTG controller?
> >> >>
> >> >
> >> > It may not be a real separate OTG controller. It can be a hardware part
> >> > (external connector, external IC, SoC OTG register area, etc) to handle vbus
> >> > ,id and other signals which are used for role swap.
> >>
> >> That's already solved. EXTCON solved that years back and OMAP has been
> >> using EXTCON to program its UTMI mailbox.
> >>
> >
> > No, that's not the same thing, it does not include the swap role.
>
> Read your original comment:
>
> "handle vbus, id and other signals which are *used for* role swap"
>
> You didn't include role swap in your original comment. Semantics aside...
>
> > Consider the use case the host driver is at host/ and udc driver is
> > at gadget/udc, how to finish to role swap?
>
> ... why does the source code placement matter? And what do you mean by
> "finish role swap"?
>
Well, it depends on your driver design, do you want the host driver's
API is still be called when current role is peripheral? One typical
problem you can refer below:
commit 11c011a5e777c83819078a18672543f04482b3ec
Author: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Date: Thu May 19 11:12:56 2016 +0100
usb: echi-hcd: Add ehci_setup check before echi_shutdown
In some cases, the USB code (gadget/hcd->start/stop) needs to be called
during the role swap. For example, if you have mux driver, you may
need to call usb_remove_hcd when ID from 0 to 1. Without Roger's framework,
how can we do that?
--
Best Regards,
Peter Chen
next prev parent reply other threads:[~2016-06-21 9:14 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-10 13:07 [PATCH v10 00/14] USB OTG/dual-role framework Roger Quadros
2016-06-10 13:07 ` [PATCH v10 01/14] usb: hcd: Initialize hcd->flags to 0 Roger Quadros
2016-06-14 8:16 ` Roger Quadros
2016-06-10 13:07 ` [PATCH v10 02/14] usb: otg-fsm: Prevent build warning "VDBG" redefined Roger Quadros
2016-06-10 13:07 ` [PATCH v10 03/14] usb: hcd.h: Add OTG to HCD interface Roger Quadros
2016-06-14 8:17 ` Roger Quadros
2016-06-14 14:21 ` Alan Stern
2016-06-15 7:14 ` Roger Quadros
2016-06-10 13:07 ` [PATCH v10 04/14] usb: otg-fsm: use usb_otg wherever possible Roger Quadros
2016-06-10 13:07 ` [PATCH v10 05/14] usb: otg-fsm: move host controller operations into usb_otg->hcd_ops Roger Quadros
2016-06-10 13:07 ` [PATCH v10 06/14] usb: gadget.h: Add OTG to gadget interface Roger Quadros
2016-06-12 9:13 ` Peter Chen
2016-06-20 7:21 ` Felipe Balbi
2016-06-20 7:28 ` Roger Quadros
2016-06-20 8:13 ` Felipe Balbi
2016-06-20 8:25 ` Roger Quadros
2016-06-20 9:24 ` Felipe Balbi
2016-06-20 9:43 ` Roger Quadros
2016-06-10 13:07 ` [PATCH v10 07/14] usb: otg: get rid of CONFIG_USB_OTG_FSM in favour of CONFIG_USB_OTG Roger Quadros
2016-06-10 13:07 ` [PATCH v10 08/14] usb: otg: add OTG/dual-role core Roger Quadros
2016-06-12 11:21 ` Peter Chen
2016-06-13 7:42 ` Roger Quadros
2016-06-13 7:56 ` [PATCH v11 " Roger Quadros
2016-06-13 7:58 ` Peter Chen
2016-06-20 7:45 ` Felipe Balbi
2016-06-20 10:13 ` Roger Quadros
2016-06-20 12:03 ` Felipe Balbi
2016-06-20 12:26 ` Roger Quadros
2016-06-20 12:46 ` Felipe Balbi
2016-06-21 6:39 ` Peter Chen
2016-06-21 7:19 ` Felipe Balbi
2016-06-21 8:02 ` Peter Chen
2016-06-21 8:18 ` Felipe Balbi
2016-06-21 9:14 ` Peter Chen
2016-06-21 12:35 ` Felipe Balbi
2016-06-21 13:12 ` Peter Chen
2016-06-21 14:47 ` Felipe Balbi
2016-06-22 3:33 ` Peter Chen
2016-06-22 6:51 ` Felipe Balbi
2016-06-22 7:30 ` Peter Chen
2016-06-22 8:00 ` Felipe Balbi
2016-06-23 7:41 ` Yoshihiro Shimoda
2016-06-21 2:30 ` Yoshihiro Shimoda
2016-06-21 7:21 ` Felipe Balbi
2016-06-20 11:49 ` Peter Chen
2016-06-20 12:08 ` Felipe Balbi
2016-06-21 6:05 ` Peter Chen
2016-06-21 7:26 ` Felipe Balbi
2016-06-21 9:07 ` Peter Chen [this message]
2016-06-21 10:02 ` Felipe Balbi
2016-06-21 10:43 ` Tony Lindgren
2016-06-21 10:56 ` Felipe Balbi
2016-06-21 13:05 ` Peter Chen
2016-06-22 6:56 ` Felipe Balbi
2016-06-22 7:33 ` Peter Chen
2016-06-22 8:03 ` Felipe Balbi
2016-06-22 7:49 ` Roger Quadros
2016-06-22 8:14 ` Felipe Balbi
2016-06-22 8:30 ` Roger Quadros
2017-01-19 11:56 ` Vivek Gautam
2017-01-19 12:15 ` Roger Quadros
2017-01-19 15:15 ` vivek.gautam
2017-01-20 8:30 ` Roger Quadros
2017-01-20 11:39 ` Vivek Gautam
2016-06-23 7:42 ` Yoshihiro Shimoda
2016-06-10 13:07 ` [PATCH v10 09/14] usb: of: add an API to get OTG device from USB controller node Roger Quadros
2016-06-13 8:13 ` Jun Li
2016-06-13 8:16 ` Roger Quadros
2016-06-13 8:23 ` [PATCH v11 " Roger Quadros
2016-06-10 13:07 ` [PATCH v10 10/14] usb: otg: add hcd companion support Roger Quadros
2016-06-10 13:07 ` [PATCH v10 11/14] usb: otg: use dev_vdbg() instead of VDBG() Roger Quadros
2016-06-10 13:07 ` [PATCH v10 12/14] usb: hcd: Adapt to OTG core Roger Quadros
2016-06-14 8:17 ` Roger Quadros
2016-06-10 13:07 ` [PATCH v10 13/14] usb: gadget: udc: adapt " Roger Quadros
2016-06-12 11:36 ` Peter Chen
2016-06-13 7:14 ` Roger Quadros
2016-06-13 7:20 ` Peter Chen
2016-06-13 7:37 ` Roger Quadros
2016-06-13 7:40 ` Peter Chen
2016-06-13 7:55 ` [PATCH v11 " Roger Quadros
2016-06-13 7:56 ` Peter Chen
2016-06-13 8:06 ` Roger Quadros
2016-06-10 13:07 ` [PATCH v10 14/14] usb: host: xhci-plat: Add otg device to platform data Roger Quadros
2016-06-14 8:18 ` Roger Quadros
2016-06-14 2:17 ` [PATCH v10 00/14] USB OTG/dual-role framework Peter Chen
2016-06-14 8:12 ` Roger Quadros
2016-06-16 11:07 ` Roger Quadros
2016-06-17 7:17 ` Felipe Balbi
2016-06-17 7:31 ` Roger Quadros
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