From: Peter Chen <hzpeterchen@gmail.com>
To: Felipe Balbi <balbi@kernel.org>
Cc: Roger Quadros <rogerq@ti.com>,
peter.chen@freescale.com, yoshihiro.shimoda.uh@renesas.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, 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 14:39:36 +0800 [thread overview]
Message-ID: <20160621063936.GB5108@shlinux2> (raw)
In-Reply-To: <878ty0qd7q.fsf@linux.intel.com>
On Mon, Jun 20, 2016 at 03:03:37PM +0300, Felipe Balbi wrote:
>
> Hi,
>
> >>> +
> >>> + /* start host */
> >>> + ret = hcd_ops->add(otg->primary_hcd.hcd,
> >>> + otg->primary_hcd.irqnum,
> >>> + otg->primary_hcd.irqflags);
> >>
> >> this is usb_add_hcd(), is it not? Why add an indirection?
> >
> > I've introduced the host and gadget ops interface to get around the
> > circular dependency issue we can't avoid.
> > otg needs to call host/gadget functions and host/gadget also needs to
> > call otg functions.
>
> IMO, this shows a fragility of your design. You're, now, lying to
> usb_hcd and usb_udc and making them register into a virtual layer that
> doesn't exist. And that layer will end up calling the real registration
> function when some magic event happens.
>
> This is only really needed for quirky devices like dwc3 (but see more on
> dwc3 below) where host and peripheral registers shadow each
> other. Otherwise we would be able to always keep hcd and udc always
> registered. They would get different interrupt statuses anyway and
> nothing would ever break.
>
> However, when it comes to dwc3, we already have all the code necessary
> to workaround this issue by destroying the XHCI pdev when OTG interrupt
> says we should be peripheral (and vice-versa). DWC3 also keeps track of
> the OTG states for those folks who really care about OTG (Hint: nobody
> has cared for the past 10 years, why would they do so now?) and we don't
> need a SW state machine when the HW handles that for us, right?
>
> As for chipidea, IIRC, that doesn't need a SW state machine either, but
> I know very little about that IP and don't even have documentation on
> it. My understanding, however, is that chipidea behaves kinda like MUSB,
> which changes roles automatically in HW based on ID pin state.
Chipidea needs to set register for USB role manually.
> >>> + * @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?
> >>
> >
> > Andrew had pointed out in [1] that Tegra210 has separate blocks for OTG, host
> > and gadget.
> >
> > [1] http://article.gmane.org/gmane.linux.ports.tegra/22969
>
> that's not an OTG controller, it's just a mux. No different than Intel's
> mux for swapping between XHCI and peripheral-only DWC3.
>
> frankly, I would NEVER talk about OTG when type-C comes into play. They
> are two competing standards and, apparently, type-C is winning when it
> comes to role-swapping.
>
In fact, OTG is mis-used by people. Currently, if the port is dual-role,
It will be considered as an OTG port.
You are right, if the connector is type-c, it will be called as "type-c
port" by people :)
--
Best Regards,
Peter Chen
next prev parent reply other threads:[~2016-06-21 6:46 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 [this message]
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
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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