Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754917AbbDNL3r (ORCPT ); Tue, 14 Apr 2015 07:29:47 -0400 Received: from mailout2.samsung.com ([203.254.224.25]:34887 "EHLO mailout2.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753137AbbDNL3g (ORCPT ); Tue, 14 Apr 2015 07:29:36 -0400 X-AuditID: cbfee68e-f79c56d000006efb-f9-552cfa1e6012 Message-id: <552CFA1E.5070400@samsung.com> Date: Tue, 14 Apr 2015 20:29:34 +0900 From: Chanwoo Choi User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130106 Thunderbird/17.0.2 MIME-version: 1.0 To: Roger Quadros Cc: Robert Baldyga , myungjoo.ham@samsung.com, linux-usb@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, m.szyprowski@samsung.com, "Balbi, Felipe" , "ABRAHAM, KISHON VIJAY" , Peter Chen Subject: Re: [PATCH v3 2/4] extcon: usb-gpio: add support for VBUS detection References: <1427980385-21285-1-git-send-email-r.baldyga@samsung.com> <1427980385-21285-3-git-send-email-r.baldyga@samsung.com> <5525E012.5050207@samsung.com> <552630E4.9030309@samsung.com> <55264148.8070903@samsung.com> <55264534.4020006@samsung.com> <55277910.2070000@samsung.com> <55277FA2.6090700@samsung.com> <55278580.2090809@samsung.com> <55278DD3.3020409@samsung.com> <55279550.1060609@samsung.com> <552CE579.6060702@ti.com> <552CE5C0.3010207@ti.com> <552CEC97.1050205@samsung.com> <552CEE42.1050907@ti.com> In-reply-to: <552CEE42.1050907@ti.com> Content-type: text/plain; charset=UTF-8 Content-transfer-encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFlrDIsWRmVeSWpSXmKPExsWyRsSkSFful06owddDehYH79dbzD9yjtXi wtMeNovLu+awWSxa1spssfbIXXaL240r2CyOzf7LZPHg8E52i55HWg5cHv8O9zN59G1Zxehx /MZ2Jo/Pm+QCWKK4bFJSczLLUov07RK4Mn6cXMVecEm/YsWfe6wNjF/Vuhg5OSQETCSu9cxl hbDFJC7cW8/WxcjFISSwlFFiVfdyZpiivhcnGCESixglHh6fwQrhPGCUWHGplQ2kildAS+Jm /wuwDhYBVYllveeZQGw2oPj+FzfAakQFwiRWTr/CAlEvKPFj8j0wW0RAUeLeyvVgNcwCq5kk 1t9N6mLk4BAW8JFYeANq12QWiU+XZ4GdyimgJnH56DZWiHp1iUnzFjFD2PISm9e8ZQZpkBC4 xi5xb8sidoiDBCS+TT7EAjJUQkBWYtMBqM8kJQ6uuMEygVFsFpKTZiEZOwvJ2AWMzKsYRVML kguKk9KLjPSKE3OLS/PS9ZLzczcxAiPx9L9nfTsYbx6wPsQowMGoxMN7wkcnVIg1say4MvcQ oynQFROZpUST84HxnlcSb2hsZmRhamJqbGRuaaYkzpsg9TNYSCA9sSQ1OzW1ILUovqg0J7X4 ECMTB6dUA6OdxvOPhf6aVtV3prgd5Ttf6fGD9+7dWdemp1hPL+JU22p6w1y1YqbHsg03Dy6s fj3zJdOyzq95vHE99+QWR0h1LjkYdfiOspNC1CTL2om3otdqNQax/awKa9Rwmx3x5r8uX9Dn 97HTT/qUNGbd5Q2W4q+SerjPtO5EjsGRKy0fup6+mWj84rcSS3FGoqEWc1FxIgDcgmUsvwIA AA== X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFvrGIsWRmVeSWpSXmKPExsVy+t9jAV25XzqhBkd+qVgcvF9vMf/IOVaL C0972Cwu75rDZrFoWSuzxdojd9ktbjeuYLM4Nvsvk8WDwzvZLXoeaTlwefw73M/k0bdlFaPH 8RvbmTw+b5ILYIlqYLTJSE1MSS1SSM1Lzk/JzEu3VfIOjneONzUzMNQ1tLQwV1LIS8xNtVVy 8QnQdcvMAbpHSaEsMacUKBSQWFyspG+HaUJoiJuuBUxjhK5vSBBcj5EBGkhYw5jx4+Qq9oJL +hUr/txjbWD8qtbFyMkhIWAi0ffiBCOELSZx4d56ti5GLg4hgUWMEg+Pz2CFcB4wSqy41MoG UsUroCVxs/8FM4jNIqAqsaz3PBOIzQYU3//iBliNqECYxMrpV1gg6gUlfky+B2aLCChK3Fu5 HqyGWWA1k8T6u0ldjBwcwgI+EgtvQO2azCLx6fIsVpAaTgE1ictHt7FC1KtLTJq3iBnClpfY vOYt8wRGgVlIVsxCUjYLSdkCRuZVjKKpBckFxUnpuUZ6xYm5xaV56XrJ+bmbGMFx/kx6B+Oq BotDjAIcjEo8vCd8dEKFWBPLiitzDzFKcDArifCe/A4U4k1JrKxKLcqPLyrNSS0+xGgKDIGJ zFKiyfnAFJRXEm9obGJmZGlkbmhhZGyuJM47R1cuVEggPbEkNTs1tSC1CKaPiYNTqoFxlcga 5sr1P198Wuy17fv5BX4C1R37nm6dsFdtb2Dlt/MswrISHioTNJteT9Pnf9lQ8Fu/rSbhaUjV tFx+xhPtDz+E/m6fZhHk+XGJ+8MPgVNLpxUKHLfsM+NyNZr0Z+/FoKz1fhPZN/2dtu/KjU5e 3ooJkurFTfO3CX4VWKC/r3BZTtGdsu67SizFGYmGWsxFxYkA0nGIAgkDAAA= DLP-Filter: Pass X-MTR: 20000000000000000@CPGS X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6212 Lines: 136 On 04/14/2015 07:38 PM, Roger Quadros wrote: > On 14/04/15 13:31, Chanwoo Choi wrote: >> On 04/14/2015 07:02 PM, Roger Quadros wrote: >>> Fixed Kishon's id. >>> >>> On 14/04/15 13:01, Roger Quadros wrote: >>>> On 10/04/15 12:18, Chanwoo Choi wrote: >>>>> On 04/10/2015 05:46 PM, Robert Baldyga wrote: >>>>>> On 04/10/2015 10:10 AM, Chanwoo Choi wrote: >>>>>>> On 04/10/2015 04:45 PM, Robert Baldyga wrote: >>>>>>>> On 04/10/2015 09:17 AM, Chanwoo Choi wrote: >>>>>>>>> Hi Robert, >>>>>>>>> >>>>>>>>> On 04/09/2015 06:24 PM, Robert Baldyga wrote: >>>>>>>>>> Hi Chanwoo, >>>>>>>>>> >>>>>>>>>> On 04/09/2015 11:07 AM, Chanwoo Choi wrote: >>>>>>>>>>> Hi Robert, >>>>>>>>>>> >>>>>>>>>>> On 04/09/2015 04:57 PM, Robert Baldyga wrote: >>>>>>>>>>>> Hi Chanwoo, >>>>>>>>>>>> >>>>>>>>>>>> On 04/09/2015 04:12 AM, Chanwoo Choi wrote: >>>>>>>>>>>>> Hi Robert, >>>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> [snip] >>>>>>>>>>> >>>>>>>>>>>>> But, I have one question about case[3] >>>>>>>>>>>>> >>>>>>>>>>>>> If id is low and vbus is high, this patch will update the state of both USB and USB-HOST cable as attached state. >>>>>>>>>>>>> Is it possible that two different cables (both USB and USB-HOST) are connected to one port simultaneously? >>>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> It's because state of single USB cable connection cannot be completely >>>>>>>>>>>> described using single extcon cable. USB cable state has two bits (VBUS >>>>>>>>>>>> and ID), so we need to use two cables for single cable connection. We >>>>>>>>>>>> use following convention: >>>>>>>>>>>> cable "USB" = VBUS >>>>>>>>>>>> cable "USB-HOST" = !ID. >>>>>>>>>>> >>>>>>>>>>> I think that extcon provider driver have to update the only one cable state >>>>>>>>>>> of either USB or USB-HOST because USB and USB-HOST feature can not be used >>>>>>>>>>> at the same time through one h/w port. >>>>>>>>>>> >>>>>>>>>>> If extcon-usb-gpio.c update two connected event of both USB and USB-HOST cable >>>>>>>>>>> at the same time, the extcon consumer driver can not decide what handle either USB or USB-HOST. >>>>>>>>>>> >>>>>>>>>> >>>>>>>>>> It can. USB OTG allows for that. Moreover device can be host even if >>>>>>>>>> ID=1 (so detected cable type is USB device), or peripheral when ID=0 (so >>>>>>>>>> detected cable type is USB host). Devices would need to have complete >>>>>>>>>> information about USB cable connection, because OTG state machine needs >>>>>>>>> >>>>>>>>> As I knew, USB OTG port don't send the attached cable of both USB and USB-HOST >>>>>>>>> at the same time. The case3 in your patch update two cable state about one h/w port. >>>>>>>>> >>>>>>>> >>>>>>>> It's because simple "USB" or "USB-HOST" means nothing for USB OTG >>>>>>>> machine. It needs to know exact VBUS and ID states, which cannot be >>>>>>>> concluded basing on cable type only. That's why I have used "USB-HOST" >>>>>>>> name together with "USB" to pass additional information about USB cable >>>>>>>> connection. >>>>>>> >>>>>>> I think this method is not proper to support this case. >>>>>>> It may cause the confusion about other case using USB/USB-HOST cable state >>>>>>> except of you commented case. >>>>>> >>>>>> That's why I finally proposed to use "USB-ID" and "USB-VBUS" in parallel >>>>>> with old names. It seems to be simpler solution than adding new >>>>>> mechanism notifying about VBUS and ID states changes. >>>>> >>>>> >>>>> As I commented on previous reply, I don't agree to use 'USB-ID' and 'USB-VBUS'. >>>>> If we add new strange 'USB-ID' and 'USB-VBUS' name, we would add non-general cable >>>>> name continuoulsy. >>>>> >>>>> I think that extcon core provide the helper API to get the value of VBUS. >>>>> But I need to consider it. >>>> >>>> Now it is starting to look like existing extcon states are not suitable for USB/PHY drivers to deliver >>>> VBUS and ID information reliably. >>>> This is because based on your comments the "USB" and "USB-HOST" states look like some fuzzy states >>>> and have no direct correspondence with "VBUS" and "ID". The fact that they can't become >>>> attached simultaneously makes me conclude that "USB" and "USB-HOST" cable states are really >>>> capturing only the ID pin state. >>>> >>>> I can suggest the following options >>>> a) let "USB" and "USB-HOST" only indicate ID pin status. Add a new cable state for "VBUS" notification. >>>> Maybe call it "USB-POWER" or something. >> >> We must discuss it before using the new cable name >> such as "USB-POWER", "USB-ID" and "USB-VBUS". > > I didn't say to add "USB-ID" or "USB-VBUS". solution (a) was to have the following Right. Robert suggested the "USB-ID" and "USB-VBUS" cable name on previous mail in mail thread. > "USB" - attached means ID is high. i.e. Type-B plug attached. > "USB-HOST" - attached means ID is low. i.e. Type-A plug attached. > "USB-POWER" - attached means USB power is present. i.e. VBUS is alive. > > This way the definition of USB and USB-HOST remain true to their name and avoid further confusions. > VBUS state is got through the "USB-POWER" cable state. There is the same case for MHL cable. Also, MHL cable could be connected to VBUS line. - MHL : attached just MHL cable. - MHL-POWER : attache MHL cable which is connected with VBUS line. We must need the opinion of USB/PHY driver's maintainer. > >> >> What is the appropriate method of following two solution? >> - Fisrt, use the new cable name "USB-*". > I explained this above. > >> - Second, use the additional API to get the VBUS state. > > You keep mentioning additional API for VBUS. But I don't see any such API. Can you please > suggest what API you are talking about? I'm considering following functions for VBUS state. But it is my opinion, If USB/PHY drivers's maintainers don't agree the new cable ("USB-POWER"), We could use the following function to get VBUS state. Because new cable name will affect the USB/PHY drivers. - int extcon_{get|set}_vbus_state(struct extcon_dev *edev); Cheers, Chanwoo Choi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/