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From: Felipe Balbi <balbi-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
To: Peter Chen <hzpeterchen-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: Roger Quadros <rogerq-l0cyMroinI0@public.gmane.org>,
	peter.chen-KZfg59tc24xl57MIdRCFDg@public.gmane.org,
	yoshihiro.shimoda.uh-zM6kxYcvzFBBDgjK7y7TUQ@public.gmane.org,
	tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org,
	gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org,
	dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org,
	mathias.nyman-VuQAYsv1563Yd54FQh9/CA@public.gmane.org,
	Joao.Pinto-HKixBCOQz3hWk0Htik3J/w@public.gmane.org,
	sergei.shtylyov-M4DtvfQ/ZS1MRgGoP+s0PdBPR1lH4CV8@public.gmane.org,
	jun.li-KZfg59tc24xl57MIdRCFDg@public.gmane.org,
	grygorii.strashko-l0cyMroinI0@public.gmane.org,
	robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org,
	nsekhar-l0cyMroinI0@public.gmane.org,
	b-liu-l0cyMroinI0@public.gmane.org,
	joe-6d6DIl74uiNBDgjK7y7TUQ@public.gmane.org,
	linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.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: 3813 bytes --]


Hi,

Peter Chen <hzpeterchen-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 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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  reply	other threads:[~2016-06-22  6:51 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
     [not found]   ` <1465564043-27163-2-git-send-email-rogerq-l0cyMroinI0@public.gmane.org>
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
     [not found]     ` <575FBD8D.7090700-l0cyMroinI0@public.gmane.org>
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
     [not found] ` <1465564043-27163-1-git-send-email-rogerq-l0cyMroinI0@public.gmane.org>
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
     [not found]         ` <57679B30.6030809-l0cyMroinI0@public.gmane.org>
2016-06-20  8:13           ` Felipe Balbi
     [not found]             ` <87d1ncxopa.fsf-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2016-06-20  8:25               ` Roger Quadros
     [not found]                 ` <5767A87C.20704-l0cyMroinI0@public.gmane.org>
2016-06-20  9:24                   ` Felipe Balbi
     [not found]                     ` <87inx4qkka.fsf-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2016-06-20  9:43                       ` Roger Quadros
2016-06-10 13:07   ` [PATCH v10 08/14] usb: otg: add OTG/dual-role core Roger Quadros
     [not found]     ` <1465564043-27163-9-git-send-email-rogerq-l0cyMroinI0@public.gmane.org>
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
     [not found]         ` <575E672E.5070603-l0cyMroinI0@public.gmane.org>
2016-06-20  7:45           ` Felipe Balbi
     [not found]             ` <87h9coxq04.fsf-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2016-06-20 10:13               ` Roger Quadros
2016-06-20 12:03                 ` Felipe Balbi
     [not found]                   ` <878ty0qd7q.fsf-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
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
     [not found]                           ` <87mvmfneeq.fsf-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
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
     [not found]                                     ` <874m8mmwdo.fsf-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2016-06-22  3:33                                       ` Peter Chen
2016-06-22  6:51                                         ` Felipe Balbi [this message]
     [not found]                                           ` <87shw5lnrs.fsf-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2016-06-22  7:30                                             ` Peter Chen
2016-06-22  8:00                                               ` Felipe Balbi
2016-06-23  7:41                                         ` Yoshihiro Shimoda
     [not found]                 ` <5767C1B9.2060805-l0cyMroinI0@public.gmane.org>
2016-06-21  2:30                   ` Yoshihiro Shimoda
     [not found]                     ` <SG2PR06MB0919045392F2545FF85033CED82B0-ESzmfEwOt/zNQ8RBPPB5A20DtJ1/0DrXvxpqHgZTriW3zl9H0oFU5g@public.gmane.org>
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
     [not found]                       ` <877fdjovef.fsf-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2016-06-21  9:07                         ` Peter Chen
2016-06-21 10:02                           ` Felipe Balbi
     [not found]                             ` <87h9cmoo4s.fsf-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
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
     [not found]                                               ` <3c95b592d78aa569de33d420c4c93018-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
2017-01-20  8:30                                                 ` Roger Quadros
2017-01-20 11:39                                                   ` Vivek Gautam
     [not found]                                     ` <576A4321.6020209-l0cyMroinI0@public.gmane.org>
2016-06-23  7:42                                       ` Yoshihiro Shimoda
2016-06-10 13:07   ` [PATCH v10 13/14] usb: gadget: udc: adapt to OTG core Roger Quadros
     [not found]     ` <1465564043-27163-14-git-send-email-rogerq-l0cyMroinI0@public.gmane.org>
2016-06-12 11:36       ` Peter Chen
2016-06-13  7:14         ` Roger Quadros
     [not found]           ` <575E5D57.7010700-l0cyMroinI0@public.gmane.org>
2016-06-13  7:20             ` Peter Chen
2016-06-13  7:37               ` Roger Quadros
     [not found]                 ` <575E62D7.8010409-l0cyMroinI0@public.gmane.org>
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 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 09/14] usb: of: add an API to get OTG device from USB controller node Roger Quadros
     [not found]   ` <1465564043-27163-10-git-send-email-rogerq-l0cyMroinI0@public.gmane.org>
2016-06-13  8:13     ` Jun Li
     [not found]       ` <AM4PR04MB213007B012120B6FF67F869689530-WOempg8NbQQzjTQnahXoOs9NdZoXdze2vxpqHgZTriW3zl9H0oFU5g@public.gmane.org>
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 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
     [not found]   ` <5762887A.4060606-l0cyMroinI0@public.gmane.org>
2016-06-17  7:17     ` Felipe Balbi
2016-06-17  7:31       ` Roger Quadros

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