From: Peter Chen <hzpeterchen@gmail.com>
To: Felipe Balbi <balbi@kernel.org>, yoshihiro.shimoda.uh@renesas.com
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: Wed, 22 Jun 2016 11:33:56 +0800 [thread overview]
Message-ID: <20160622033356.GB21361@shlinux2> (raw)
In-Reply-To: <874m8mmwdo.fsf@linux.intel.com>
On Tue, Jun 21, 2016 at 05:47:47PM +0300, Felipe Balbi wrote:
>
> Hi,
>
> Peter Chen <hzpeterchen@gmail.com> writes:
> >> >> >> >> >>> + * @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.
> >> >> >>
> >> >> >> That's because "dual-role" is a non-standard OTG. Seen as people really
> >> >> >> didn't care about OTG, we (linux-usb folks) ended up naturally referring
> >> >> >> to "non-standard OTG" as "dual-role". Just to avoid confusion.
> >> >> >
> >> >> > So, unless we use OTG FSM defined in OTG spec, we should not mention
> >> >> > "OTG" in Linux, right?
> >> >>
> >> >> to avoid confusion with the terminology, yes. With that settled, let's
> >> >> figure out how you can deliver what your marketting guys are asking of
> >> >> you.
> >> >>
> >> >
> >> > Since nxp SoC claims they are OTG compliance, we need to pass usb.org
> >> > test. The internal bsp has passed PET test, and formal compliance test
> >> > is on the way (should pass too).
> >> >
> >> > The dual-role and OTG compliance use the same zImage, but different
> >> > dtb.
> >>
> >> okay, that's good to know. Now, the question really is: considering we
> >> only have one user for this generic OTG FSM layer, do we really need to
> >> make it generic at all? I mean, just look at how invasive a change that
> >> is.
> >
> > If the chipidea is the only user for this roger's framework, I don't
> > think it is necessary. In fact, Roger introduces this framework, and
> > the first user is dwc3, we think it can be used for others. Let's
>
> Right, we need to look at the history of dwc3 to figure out why the
> conclusion that dwc3 needs this was made.
>
> Roger started working on this framework when Power on Reset section of
> databook had some details which weren't always clear and, for safety, we
> always had reset asserted for a really long time. It was so long (about
> 400 ms) that resetting dwc3 for each role swap was just too much.
>
> Coupled with that, the OTG chapter wasn't very clear either on
> expections from Host and Peripheral side initialization in OTG/DRD
> systems.
>
> More recent version of dwc3 databook have a much better description of
> how and which reset bits _must_ be asserted and which shouldn't be
> touched unless it's for debugging purposes. When I implemented that, our
> ->probe() went from 400ms down to about 50us.
>
> Coupled with that, the OTG chapter also became a lot clearer to the
> point that it states you just don't initialize anything other than the
> OTG block, and just wait for OTG interrupt to do whatever it is you need
> to do.
>
> This meant that we could actually afford to do full reinitialization of
> dwc3 on role swap (it's now only 50us anyway) and we knew how to swap
> roles properly.
>
> (The reason for needing soft-reset during role swap is kinda long. But
> in summary dwc3 shadows register writes to both host and peripheral
> sides)
>
> > just discuss if it is necessary for dual-role switch.
>
> fair. However, if we have a single user we don't have a Generic
> layer. There's not enough variance to come up with truly generic
> architecture for this.
>
> --
I have put some points in my last reply [1], I summery it here to
see if a generic framework is deserved or not?
1. If there are some parts we can use during the role switch
- The common start/stop host and peripheral operation
eg, when switch from host to peripheral, all drivers can use
usb_remove_hcd to finish it.
- A common workqueue to handle vbus and id event
- sysfs for role switch
2. Does a mux driver can do it well? Yoshihiro, here we need your
point. The main point is if we need to call USB API to change
roles (eg, usb_remove_hcd) during the role switch, thanks.
[1] http://www.spinics.net/lists/linux-usb/msg142974.html
--
Best Regards,
Peter Chen
next prev parent reply other threads:[~2016-06-22 3:40 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 [this message]
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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