linux-kernel - Re: [PATCH] net/wireless: enable wiphy device to suspend/resume asynchronously

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Date:	Sat, 19 Sep 2015 10:45:11 +0800
From:	"Fu, Zhonghui" <zhonghui.fu@...ux.intel.com>
To:	Johannes Berg <johannes@...solutions.net>,
	Arend van Spriel <arend@...adcom.com>,
	Emmanuel Grumbach <egrumbach@...il.com>
CC:	David Miller <davem@...emloft.net>,
	"linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH] net/wireless: enable wiphy device to suspend/resume asynchronously



On 2015/8/24 15:38, Johannes Berg wrote:
> On Mon, 2015-08-24 at 11:45 +0800, Fu, Zhonghui wrote:
>> On 2015/8/17 16:46, Arend van Spriel wrote:
>>> + Rafael
>>>
>>> On 08/17/2015 09:29 AM, Johannes Berg wrote:
>>>> On Mon, 2015-08-17 at 09:48 +0800, Fu, Zhonghui wrote:
>>>>> The suspend/resume timing of wiphy device and related devices 
>>>>> will be
>>>>> ensured by their parent/child relationship. So, enabling wiphy 
>>>>> device
>>>>> to suspend/resume asynchronously does not change any 
>>>>>  dependency. It
>>>>> can only take advantage of multicore and improve system
>>>>> suspend/resume speed.
>>>>>
>>>> You're going to have to explain that to me, because I don't see 
>>>> that.
>>>> All I see is that when looking at a device, if async is possible, 
>>>> it
>>>> gets added to an async work, and if async is not possible then it 
>>>> gets
>>>> done immediately. Even putting aside the question of whether or 
>>>> not
>>>> async is ordered or not (I don't know), if the wiphy is async and 
>>>> the
>>>> PCI (or other bus) device isn't, then it seems they could get 
>>>> handled
>>>> out of order, no? Or is there some magic code somewhere that I'm
>>>> missing that explicitly waits for the async of the parent/child
>>>> relationship?
>>> This patch got me worried as well. Can't find the magic either. 
>>> Maybe Rafael can give some hints here.
>> "dpm_wait_for_children" function will be invoked in 
>> "__device_suspend", "__device_suspend_late", and 
>> "__device_suspend_noirq" functions to synchronize the child 
>> relationship. "dpm_wait" function will be invoked in 
>> "device_resume_noirq", "device_resume_early", and "device_resume" 
>> functions to synchronize the parent relationship. If two devices have 
>> parent/child relationship, but different suspend/resume mode(sync or 
>> async), this will have no impact to PM timing order between them. 
>> Because all devices will use "__device_suspend", 
>> "__device_suspend_late" ... functions to complete their PM 
>> transition.
>>
> Ok, good point. For the unaware here, can you please resend with a
> commit message amended with some of this information?
I take some leaves these days, so very sorry for late reply.

I have resent this patch with your advices - "[PATCH v2] net/wireless: enable wiphy device to suspend/resume asynchronously".


Thanks,
Zhonghui
>
> thanks,
> johannes

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