From: Roger Quadros <rogerq-l0cyMroinI0@public.gmane.org>
To: Chanwoo Choi <cw00.choi-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
Cc: Robert Baldyga
<r.baldyga-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>,
myungjoo.ham-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org,
linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
m.szyprowski-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org, "Balbi,
Felipe" <balbi-l0cyMroinI0@public.gmane.org>,
"ABRAHAM, KISHON VIJAY" <kishon-l0cyMroinI0@public.gmane.org>,
Peter Chen <peter.chen-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
Subject: Re: [PATCH v3 2/4] extcon: usb-gpio: add support for VBUS detection
Date: Tue, 14 Apr 2015 13:38:58 +0300 [thread overview]
Message-ID: <552CEE42.1050907@ti.com> (raw)
In-Reply-To: <552CEC97.1050205-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
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
"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.
>
> 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?
cheers,
-roger
>
> Cheers,
> Chanwoo Choi
>
>>>
>>> NOTE: "USB-POWER" can become attached simultaneously with "USB" or "USB-HOST". But "USB-POWER" is now really
>>> a different cable like "Fast-Charger" or "Slow-Charger".
>>>
>>> b) stop using extcon framework for USB VBUS and ID notification.
>
>
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next prev parent reply other threads:[~2015-04-14 10:38 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-02 13:13 [PATCH v3 0/4] extcon: usb-gpio: fixes and improvements Robert Baldyga
2015-04-02 13:13 ` [PATCH v3 1/4] extcon: usb-gpio: register extcon device before IRQ registration Robert Baldyga
2015-04-03 0:09 ` Chanwoo Choi
2015-04-02 13:13 ` [PATCH v3 2/4] extcon: usb-gpio: add support for VBUS detection Robert Baldyga
2015-04-02 14:02 ` Roger Quadros
[not found] ` <1427980385-21285-3-git-send-email-r.baldyga-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
2015-04-09 2:12 ` Chanwoo Choi
2015-04-09 7:57 ` Robert Baldyga
[not found] ` <552630E4.9030309-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
2015-04-09 9:07 ` Chanwoo Choi
2015-04-09 9:24 ` Robert Baldyga
[not found] ` <55264534.4020006-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
2015-04-09 9:59 ` Roger Quadros
2015-04-09 10:18 ` Robert Baldyga
2015-04-10 7:39 ` Chanwoo Choi
2015-04-10 7:17 ` Chanwoo Choi
2015-04-10 7:45 ` Robert Baldyga
2015-04-10 8:10 ` Chanwoo Choi
2015-04-10 8:46 ` Robert Baldyga
2015-04-10 9:18 ` Chanwoo Choi
2015-04-10 9:42 ` Robert Baldyga
2015-04-14 10:01 ` Roger Quadros
[not found] ` <552CE579.6060702-l0cyMroinI0@public.gmane.org>
2015-04-14 10:02 ` Roger Quadros
[not found] ` <552CE5C0.3010207-l0cyMroinI0@public.gmane.org>
2015-04-14 10:31 ` Chanwoo Choi
[not found] ` <552CEC97.1050205-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
2015-04-14 10:38 ` Roger Quadros [this message]
2015-04-14 11:29 ` Chanwoo Choi
2015-04-15 3:27 ` Peter Chen
2015-04-15 7:50 ` Roger Quadros
2015-04-15 9:26 ` Chanwoo Choi
[not found] ` <552E2EBF.5090906-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
2015-04-16 1:59 ` Peter Chen
2015-04-16 7:00 ` Chanwoo Choi
[not found] ` <552F5E17.5020902-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
2015-04-16 7:13 ` Ivan T. Ivanov
[not found] ` <1429168424.26621.1.camel-NEYub+7Iv8PQT0dZR+AlfA@public.gmane.org>
2015-04-16 7:59 ` Chanwoo Choi
[not found] ` <552F6BE3.5080604-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
2015-04-16 8:01 ` Peter Chen
2015-04-16 8:26 ` Chanwoo Choi
[not found] ` <552F724A.1050500-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
2015-04-30 7:32 ` Roger Quadros
2015-04-30 7:55 ` Chanwoo Choi
2015-04-30 8:04 ` Roger Quadros
2015-04-16 7:59 ` Peter Chen
2015-04-16 7:16 ` Roger Quadros
2015-04-02 13:13 ` [PATCH v3 3/4] extcon: usb-gpio: make debounce value configurable in devicetree Robert Baldyga
2015-04-02 13:13 ` [PATCH v3 4/4] Documentation: extcon: usb-gpio: update usb-gpio binding description Robert Baldyga
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