linux-kernel - Re: [PATCH v2] extcon: usb-gpio: Don't miss event during suspend/resume

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Date:	Mon, 11 Apr 2016 22:17:03 +0900
From:	Chanwoo Choi <cwchoi00@...il.com>
To:	Roger Quadros <rogerq@...com>
Cc:	Grygorii Strashko <grygorii.strashko@...com>,
	"myungjoo.ham@...sung.com" <myungjoo.ham@...sung.com>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] extcon: usb-gpio: Don't miss event during suspend/resume

Hi Roger,

On Mon, Apr 11, 2016 at 8:39 PM, Roger Quadros <rogerq@...com> wrote:
> Chanwoo,
>
> On 11/04/16 14:12, Chanwoo Choi wrote:
>> On 2016년 04월 11일 17:37, Grygorii Strashko wrote:
>>> On 04/11/2016 03:31 AM, Chanwoo Choi wrote:
>>>> Hi Roger,
>>>>
>>>> On 2016년 04월 08일 16:34, Roger Quadros wrote:
>>>>> Pin state might have changed during suspend/resume while
>>>>> our interrupts were disabled and if device doesn't support wakeup.
>>>>>
>>>>> Scan for change during resume for such case.
>>>>>
>>>>> Signed-off-by: Roger Quadros <rogerq@...com>
>>>>> ---
>>>>> v2:
>>>>> - only check for state change during resume if device wakeup is not supported
>>>>>
>>>>>   drivers/extcon/extcon-usb-gpio.c | 2 ++
>>>>>   1 file changed, 2 insertions(+)
>>>>>
>>>>> diff --git a/drivers/extcon/extcon-usb-gpio.c b/drivers/extcon/extcon-usb-gpio.c
>>>>> index bc61d11..118f8ab 100644
>>>>> --- a/drivers/extcon/extcon-usb-gpio.c
>>>>> +++ b/drivers/extcon/extcon-usb-gpio.c
>>>>> @@ -185,6 +185,8 @@ static int usb_extcon_resume(struct device *dev)
>>>>>    int ret = 0;
>>>>>
>>>>>    enable_irq(info->id_irq);
>>>>> +  if (!device_may_wakeup(dev))
>>>>> +          usb_extcon_detect_cable(&info->wq_detcable.work);
>>>>
>>>> The device_may_wakeup() check the following two states:
>>>> - dev->power.can_wakeup - device_init_wakeup() function set the this field.
>>>> - dev->power.wakeup - device_wakeup_enable() function set the this field.
>>>>
>>>> The probe function of extcon-usb-gpio.c always call the 'device_init_wakeup(dev,true).
>>>> But, anywhere in extcon-usb-gpio.c don't handle the device_wakeup_enable() for dev->power.wakeup.
>>>
>>>
>>> device_init_wakeup()
>>>  |-> device_wakeup_enable()
>>>
>>>>
>>>> In the extcon-usb-gpio.c, device_may_wakeup(dev) return always 'false'.
>>>> If you use the only device_may_wakeup(),
>>>> device_may_wakeup() is not able to check whether interrupt is wakeup source or not.
>>>>
>>>
>>> This check is correct and it also will take into account wake up settings changes
>>> which can be made through sysfs: /sys/.../devX/power/wakeup
>>>
>>
>> To Grygorii,
>>
>> You're right. I was mistaken. Again, I analyzed the sequence about wakeup.
>> Thanks for your reply.
>>
>> 1. Register device as wakeup_source.
>>  device_init_wakeup(dev, true) on probe()
>>       device_wakeup_enable(dev)
>>               device_source_register(const char *name)
>>                       struct wakeup_source *ws;
>>                       ws = wakeup_source_create(name)
>>                       if (ws)
>>                               wakeup_source_add(ws);
>>                                       ...
>>                                       list_add_rcu(&ws->entry, &wakeup_sources);
>>                                       ...
>>                       return ws;
>>
>>
>> 2. Register the interrupt as wake_irq
>> dev_pm_set_wake_irq(struct device *dev, int irq) on probe()
>>       struct wake_irq *wirq;
>>       wirq->dev = dev;
>>       wirq->irq = irq;
>>       dev_pm_attach_wake_irq(dev, irq, wirq);
>>               device_wakeup_attach_irq(*dev, *wakeirq)
>>                       struct wakeup_source *ws;
>>                       ws = dev->power.wakeup;
>>                       ws->wakeirq = wakeirq;
>>
>>
>> 3. Enable irq wake if device is already registed to wakeup_sources.
>> dpm_suspend_noirq()
>>       device_wakeup_arm_wake_irqs()
>>               list_for_each_entry_rcu(ws, &wakeup_sources, entry) {
>>                       if (ws->wakeirq)
>>                               dev_pm_arm_wake_irq(sw->wakeirq);
>>                                       if (device_may_wakeup(wirq->dev))
>>                                               enable_irq_wake(wirq->irq);
>>
>>
>> To Roger,
>>
>> How about using the queue_delayed_work() instead of direct call function?
>> Because the spent time of wakeup from suspend state should be fast.
>> So, I think that you better to use the queue_delayed_work().
>>
>> diff --git a/drivers/extcon/extcon-usb-gpio.c b/drivers/extcon/extcon-usb-gpio.c
>> index 118f8ab3be73..f6cbdfe31519 100644
>> --- a/drivers/extcon/extcon-usb-gpio.c
>> +++ b/drivers/extcon/extcon-usb-gpio.c
>> @@ -186,7 +186,9 @@ static int usb_extcon_resume(struct device *dev)
>>
>>         enable_irq(info->id_irq);
>>         if (!device_may_wakeup(dev))
>> -               usb_extcon_detect_cable(&info->wq_detcable.work);
>> +               queue_delayed_work(system_power_efficient_wq,
>> +                               &info->wq_detcable,
>> +                               info->debounce_jiffies);
>
> Why not to just use queue_work() instead of queue_delayed_work()
> as don't need to debounce the input?

The use of queue_work() is good.

Thanks,
Chanwoo Choi