From: Felipe Balbi <balbi@kernel.org>
To: Peter Chen <hzpeterchen@gmail.com>, 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 09:51:19 +0300 [thread overview]
Message-ID: <87shw5lnrs.fsf@linux.intel.com> (raw)
In-Reply-To: <20160622033356.GB21361@shlinux2>
[-- Attachment #1: Type: text/plain, Size: 3783 bytes --]
Hi,
Peter Chen <hzpeterchen@gmail.com> writes:
>> >> >> > 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 UDC such as dwc3 already implements start/stop for peripheral and
host. Why would go through and indirection layer that just comes back to
us? (well, dwc3's host side, start/stop translates to adding/removing
xhci-plat's device)
> - A common workqueue to handle vbus and id event
I already have a threaded IRQ handler. Why do I need a workqueue?
> - sysfs for role switch
A generic sysfs is desirable, but I really don't know where to put it.
Maybe it's enough to go down the hwmon route and just have an agreement
of filename and contents to be written to.
--
balbi
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next prev parent reply other threads:[~2016-06-22 6:52 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 [this message]
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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