Re: [PATCH] usb: xhci-mtk: fixup mouse wakeup failure during system suspend

[Felipe Balbi]

Hi,

chunfeng yun <chunfeng.yun@xxxxxxxxxxxx> writes:
> On Tue, 2016-05-03 at 12:33 +0300, Felipe Balbi wrote:
>> Hi,
>> 
>> chunfeng yun <chunfeng.yun@xxxxxxxxxxxx> writes:
>> >> chunfeng yun <chunfeng.yun@xxxxxxxxxxxx> writes:
>> >> > On Thu, 2016-04-21 at 10:04 +0800, Chunfeng Yun wrote:
>> >> >> Click mouse after xhci suspend completion but before system suspend
>> >> >> completion, system will not be waken up by mouse if the duration of
>> >> >> them is larger than 20ms which is the device UFP's resume signaling
>> >> 
>> >> what is "them" here ? The duration of what is longer than 20ms ?
>> > They are "xhci suspend completion" and "system suspend completion";
>> >
>> > It's time duration
>> 
>> okay. So if xhci suspend takes longer than 20ms your SPM doesn't see a
>> wakeup ?
> It is not the time of xhci suspend consumed, but is the time of duration
> from xhci suspend completion to system suspend completion(after BOOT-CPU
> is turned off, SPM will be enabled to receive wakeup event)

Okay, so SPM will be the entity actually handling wakeups, right ? I'm
assuming something like this happens:

echo mem > /sys/power/state
 /* start suspending devices */
  xhci_suspend()
 /* all devices suspended */
 enable_spm()

so, if a mouse button is pressed after xhci_suspend() returns but before
enable_spm() runs, then we're gonna miss that event, am I right ?

I can't think of any way to sort this out. Let's ask on linux-pm (I've
added linux-pm to Cc list)

>> >> >> lasted. Another reason is that the SPM is not enabled before system
>> >> 
>> >> what's SPM ?
>> > It is System Power Management which is powered off when system is
>> > running in normal mode, and is powered on when system enters suspend
>> > mode. It is used to wakeup system when some wakeup sources, such as
>> > bluetooth or powerkey etc, tigger wakeup event.
>> 
>> okay, thanks
>> 
>> >> >> suspend compeltion, this causes SPM also not notice the resume signal.
>> >>            ^^^^^^^^^^
>> >>            completion
>> >> 
>> >> >> So in order to reduce the duration less than 20ms, make use of
>> >> >> syscore's suspend/resume interface.
>> >> 
>> >> no, this is the wrong approach
>> > But it seems only one workable approach from software side
>> 
>> I wouldn't say that. It seems to me SPM should be enabled earlier.
> Yes, but normally SPM should be enabled after all CPUS are turned off,
> so it's difficult to do that, I mean enable SPM before turning off CPUS

is it a requirement that SPM should be enabled only after all CPUs are
turned off ? If that's the case, then any device in the system might
have missed wakeups. This doesn't seem like a good design to me; unless
I'm missing something...

>> >> >> Because the syscore runs on irq disabled context, and xhci's
>> >> >> suspend/resume calls some sleeping functions, enable local irq
>> >> >> and then disable it during suspend/resume. This may be not a problem,
>> >> >> since only boot CPU is runing.
>> >> 
>> >> another problem :) calling local_irq_{enable,disable}() is an indication
>> >> that something's wrong.
>> > Oh!
>> >
>> > BTW: There will be warning logs if they are not called.
>> 
>> yeah, I got that :-) But it's still wrong to use
>> local_irq_{enable,disable}() the way you're using them :-)
> Yes
>
> Thank you very much.
>> 
>
>

-- 
balbi

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