Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755975AbbDOHvP (ORCPT ); Wed, 15 Apr 2015 03:51:15 -0400 Received: from bear.ext.ti.com ([192.94.94.41]:53351 "EHLO bear.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932113AbbDOHvH (ORCPT ); Wed, 15 Apr 2015 03:51:07 -0400 Message-ID: <552E1862.6090709@ti.com> Date: Wed, 15 Apr 2015 10:50:58 +0300 From: Roger Quadros User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 MIME-Version: 1.0 To: Peter Chen , Chanwoo Choi CC: Robert Baldyga , , , , , , "Balbi, Felipe" , "ABRAHAM, KISHON VIJAY" Subject: Re: [PATCH v3 2/4] extcon: usb-gpio: add support for VBUS detection References: <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> <552CFA1E.5070400@samsung.com> <20150415032734.GA29095@shlinux2> In-Reply-To: <20150415032734.GA29095@shlinux2> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7495 Lines: 159 On 15/04/15 06:27, Peter Chen wrote: > On Tue, Apr 14, 2015 at 08:29:34PM +0900, Chanwoo Choi wrote: >> 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. > > From USB/USB-PHY driver point, it needs to know id and vbus value > for their internal logic, so as extcon users, the cable name > is better to reflect meaning of id and vbus, like "USB-ID" and "USB-VBUS", > if the power is from vbus pin at USB cable, I don't think we need another > cable name "USB-POWER" even the USB/USB-PHY driver don't need it. I agree as well that this is the *best* option for USB case. Just because Chanwoo was objecting these names I suggested "USB-POWER". Chanwoo, can we simply get rid of "USB" and "USB-HOST" cables and move to "USB-ID" and "USB-VBUS"? The only reason you objected was saying that it is a strange cable name. Well this is only what we care about from USB PHY drivers and user space is not interested in it so what is the concern? > >> >>> "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); This is not suitable for us as USB drivers need VBUS notification event to come. They can't keep polling for VBUS state using this API. cheers, -roger -- 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/