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

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Date:	Mon, 23 Dec 2013 16:13:32 +0800
From:	Barry Song <21cnbao@...il.com>
To:	Chanwoo Choi <cw00.choi@...sung.com>
Cc:	rjying <rjying@...il.com>, MyungJoo Ham <myungjoo.ham@...sung.com>,
	LKML <linux-kernel@...r.kernel.org>,
	RongJun Ying <Rongjun.Ying@....com>,
	Binghua Duan <Binghua.Duan@....com>
Subject: Re: [PATCH 1/1] extcon: gpio: Add power resume support

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?

>
>>
>>>
>>>>
>>>>> So, kernel would execute proper operation about interrupt
>>>>> after wakeup from suspend state.
>>>>
>>>> kernel only save/restore the register status of gpio, how could it
>>>> know whether there is a pending interrupt if the HW doesn't do it?
>>>>
>>>>>
>>>>> I think it isn't necessary.
>>>>>
>>>>> Thanks,
>>>>> Chanwoo Choi
>>>>>
>>>>>>
>>>>>> Change-Id: I32a9e1c6646035f95765bba79a7acaccb8ce45a7
>>>>>>
>>>>>> Signed-off-by: Rongjun Ying <rongjun.ying@....com>
>>>>>> ---
>>>>>>  drivers/extcon/extcon-gpio.c |   17 +++++++++++++++++
>>>>>>  1 files changed, 17 insertions(+), 0 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/extcon/extcon-gpio.c b/drivers/extcon/extcon-gpio.c
>>>>>> index 7e0dff5..d916522 100644
>>>>>> --- a/drivers/extcon/extcon-gpio.c
>>>>>> +++ b/drivers/extcon/extcon-gpio.c
>>>>>> @@ -159,12 +159,29 @@ static int gpio_extcon_remove(struct platform_device *pdev)
>>>>>>       return 0;
>>>>>>  }
>>>>>>
>>>>>> +#ifdef CONFIG_PM_SLEEP
>>>>>> +static int gpio_extcon_resume(struct device *dev)
>>>>>> +{
>>>>>> +     struct gpio_extcon_data *extcon_data;
>>>>>> +
>>>>>> +     extcon_data = dev_get_drvdata(dev);
>>>>>> +     queue_delayed_work(system_power_efficient_wq, &extcon_data->work,
>>>>>> +                           extcon_data->debounce_jiffies);
>>>>>> +     return 0;
>>>>>> +}
>>>>>> +#endif
>>>>>> +
>>>>>> +static const struct dev_pm_ops gpio_extcon_pm_ops = {
>>>>>> +     SET_SYSTEM_SLEEP_PM_OPS(NULL, gpio_extcon_resume)
>>>>>> +};
>>>>>> +
>>>>>>  static struct platform_driver gpio_extcon_driver = {
>>>>>>       .probe          = gpio_extcon_probe,
>>>>>>       .remove         = gpio_extcon_remove,
>>>>>>       .driver         = {
>>>>>>               .name   = "extcon-gpio",
>>>>>>               .owner  = THIS_MODULE,
>>>>>> +             .pm = &gpio_extcon_pm_ops,
>>>>>>       },
>>>>>>  };
>>>>>>
>>>>>>
>>>>>
>>>>
>>>> -barry
>>
>> -barry




-barry
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