linux-kernel - Re: Re: [PATCH 1/1] extcon: gpio: Add power resume support

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Date:	Mon, 23 Dec 2013 09:02:51 +0000 (GMT)
From:	MyungJoo Ham <myungjoo.ham@...sung.com>
To:	최찬우 <cw00.choi@...sung.com>,
	Barry Song <21cnbao@...il.com>
Cc:	rjying <rjying@...il.com>, LKML <linux-kernel@...r.kernel.org>,
	RongJun Ying <Rongjun.Ying@....com>,
	Binghua Duan <Binghua.Duan@....com>
Subject: Re: Re: [PATCH 1/1] extcon: gpio: Add power resume support

> On 12/23/2013 05:13 PM, Barry Song wrote:
> > 2013/12/23 Chanwoo Choi <cw00.choi@...sung.com>:
> >> On 12/23/2013 04:36 PM, Barry Song wrote:
> >>> 2013/12/23 Chanwoo Choi <cw00.choi@...sung.com>:
> >>>> On 12/23/2013 03:10 PM, Barry Song wrote:
> >>>>> 2013/12/23 Chanwoo Choi <cw00.choi@...sung.com>:
> >>>>>> On 12/20/2013 05:09 PM, rjying wrote:
> >>>>>>> From: Rongjun Ying <rongjun.ying@....com>
> >>>>>>>
> >>>>>>> After system resume, need send extcon uevent to userspace
> >>>>>>
> >>>>>> Why did extcon send uevent after wakeup from suspend?
> >>>>>>
> >>>>>> If extcon cable is attatched or detached on suspend state,
> >>>>>> Kernel can detect the interrupt about changed state of extcon.
> >>>>>
> >>>>> irq controller has lost power in suspend, so there is no pending interrupt.
> >>>>> and HW will not pend any interrupt when we hotplug cable during sleep.
> >>>>
> >>>> No, SoC in suspend state must maintain the minimum power under 1mA
> >>>> if completed the power-optimization on suspend state.
> >>>>
> >>>> If user insert USB cable to target, the external interrupt connected to
> >>>> USB port is happened. And kernel would be waked up from suspend state
> >>>> to operate proper interrupt handler of external interrupt.
> >>>
> >>> no. not every USB supports that. that depends on the power domain design of SoC.
> >>
> >> USB is only example for gpio control in suspend state.
> >>
> >>>
> >>>>
> >>>> Also,
> >>>> Input subsystem used gpio-keys driver for power button..
> >>>> If user press power button in suspend state, target would be waked up from suspend state.
> >>>> It is same case both extcon gpio and gpio-keys of input subsystem.
> >>>
> >>> no. it depends on the SoC design. many SoC only support 1 special key
> >>> which can work as ON-KEY as wakeup source. and this kind of keys might
> >>> not be GPIO at all.
> >>> there is a special power domain which is still open for it.
> >>
> >> many SoC?
> >>
> >> As I knew, most SoC has supported various wakeup source.
> >> As you comment, if specific SoC support only one special key
> >> for wakeup from suspend state, I think it isn't common.
> >>
> >> Also,
> >> This patch isn't necessary on SoCs which support various wakeup source (e.g., external interrupt).
> >> As you comment, this issue has dependecy on specific SoC. Why did you think this common code?
> > 
> > i am not thinking this patch must be common codes but i think the
> > extcon should provide common codes to support all chips. that is what
> > a framework should consider.
> > 
> > if there is no this or things similar with this, how could extcon
> > support the chips which don't support receiving sleep gpio interrupts?
> 
> Sure, subsystem should support all cases related to this issue.
> 
> I'd like to send common patch to support all cases as we discussed.
> If some patch support all case, I would review and apply it.
> 
> Chanwoo Choi

Dear Barry and Chanwoo,


What about having a flag in extcon platform data that describes
whether this extcon-gpio requires status double checking at resume
or not?


Cheers,
MyungJoo