linux-kernel - Re: [PATCH] PM: Enable asynchronous noirq resume threads to save the resuming time

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Date:	Wed, 15 Jan 2014 14:28:13 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	"Liu, Chuansheng" <chuansheng.liu@...el.com>
Cc:	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"Brown, Len" <len.brown@...el.com>, "pavel@....cz" <pavel@....cz>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Li, Zhuangzhi" <zhuangzhi.li@...el.com>
Subject: Re: [PATCH] PM: Enable asynchronous noirq resume threads to save the resuming time

On Wednesday, January 15, 2014 12:35:16 AM Liu, Chuansheng wrote:
> Hello Rafael,
> 
> > -----Original Message-----
> > From: Rafael J. Wysocki [mailto:rjw@...ysocki.net]
> > Sent: Wednesday, January 15, 2014 6:55 AM
> > To: Liu, Chuansheng
> > Cc: gregkh@...uxfoundation.org; Brown, Len; pavel@....cz;
> > linux-pm@...r.kernel.org; linux-kernel@...r.kernel.org; Li, Zhuangzhi
> > Subject: Re: [PATCH] PM: Enable asynchronous noirq resume threads to save
> > the resuming time
> > 
> > On Tuesday, January 14, 2014 03:18:08 PM Chuansheng Liu wrote:
> > >
> > > Currently, the dpm_resume_noirq() is done synchronously, and for PCI devices
> > > pci_pm_resume_noirq():
> > >
> > > pci_pm_resume_noirq()
> > >  pci_pm_default_resume_early()
> > >   pci_power_up()
> > >    pci_raw_set_power_state()
> > > Which set the device from D3hot to D0 mostly, for every device, there will
> > > be one 10ms(pci_pm_d3_delay) to wait.
> > >
> > > Hence normally dpm_resume_noirq() will cost > 100ms, which is bigger for
> > mobile
> > > platform.
> > 
> > pci_pm_d3_delay usually is not 10 ms.  What is 10 ms is dev->d3_delay, but
> > that also is not on every platform now.
> Yes, it is d3_delay exactly, thanks your correction.
> 
> > 
> > That said the approach here makes sense, but I have two questions:
> > 
> > 1. On what systems has it been tested?
> I have been tested on Baytrail platform, and at the beginning the d3_delay is set to 0,
> but we really meet the HANG issue if we operate the device immediately sometimes,
> so currently most PCI devices in Baytrail has the 10ms delay.
> And it caused the whole resume time bigger than Clovertrail platform;

Does setting d3_delay to something smaller that 10 ms work on BayTrail?

You can try to set 5 ms and then 2.5 ms if that works and so on.  That still
would be an improvement from the 10 ms.

> > 2. What about suspend_late/resume_early?  If the _noirq things are to be
> > executed asynchronously, those should be too.
> I noticed it just taken little time often, and I cannot find out some reasons for changing them
> in theory, so if you like it, I will update them into patch V2 also:)

Yes, please do that.

Thanks!

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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