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

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Date:	Mon, 11 Apr 2016 20:12:06 +0900
From:	Chanwoo Choi <cw00.choi@...sung.com>
To:	Grygorii Strashko <grygorii.strashko@...com>,
	Roger Quadros <rogerq@...com>, myungjoo.ham@...sung.com
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] extcon: usb-gpio: Don't miss event during suspend/resume

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);
 
        return ret;
 }


Thanks,
Chanwoo Choi