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From: Kai-Heng Feng <>
To: Mika Westerberg <>
Cc: Rafael Wysocki <>,
	"Shih-Yuan Lee (FourDollars)" <>,
	Tiffany <>,
	Linux PCI <>,
	Linux PM <>,
	open list <>
Subject: Re: Thunderbolt, direct-complete and long suspend/resume time of Suspend-to-idle
Date: Thu, 12 Mar 2020 12:41:08 +0800	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

> On Mar 11, 2020, at 18:38, Mika Westerberg <> wrote:
> On Wed, Mar 11, 2020 at 01:39:51PM +0800, Kai-Heng Feng wrote:
>> Hi,
>> I am currently investigating long suspend and resume time of suspend-to-idle.
>> It's because Thunderbolt bridges need to wait for 1100ms [1] for runtime-resume on system suspend, and also for system resume.
>> I made a quick hack to the USB driver and xHCI driver to support direct-complete, but I failed to do so for the parent PCIe bridge as it always disables the direct-complete [2], since device_may_wakeup() returns true for the device:
>> 	/* Avoid direct_complete to let wakeup_path propagate. */
>> 		if (device_may_wakeup(dev) || dev->power.wakeup_path)
>> 			dev->power.direct_complete = false;
> You need to be careful here because otherwise you end up situation where
> the link is not properly trained and we tear down the whole tree of
> devices which is worse than waiting bit more for resume.

My idea is to direct-complete when there's no PCI or USB device plugged into the TBT, and use pm_reuqest_resume() in complete() so it won't block resume() or resume_noirq().

>> Once the direct-complete is disabled, system suspend/resume is used hence the delay in [1] is making the resume really slow. 
>> So how do we make suspend-to-idle faster? I have some ideas but I am not sure if they are feasible:
>> - Make PM core know the runtime_suspend() already use the same wakeup as suspend(), so it doesn't need to use device_may_wakeup() check to determine direct-complete.
>> - Remove the DPM_FLAG_NEVER_SKIP flag in pcieport driver, and use pm_request_resume() in its complete() callback to prevent blocking the resume process.
>> - Reduce the 1100ms delay. Maybe someone knows the values used in macOS and Windows...
> Which system this is? ICL?

CML-H + Titan Ridge.

> I think it is the TBT root ports only that do
> not support active link reporting. The PCIe spec is not entirely clear
> about root ports since it explictly mentions only downstream ports so
> one option would be to check for root port and that it supports gen 3
> speeds and based on that wait for max say 2 * 100ms or something like
> that.

So 200ms for rootport, but still 1100ms for downstream ports?


  reply	other threads:[~2020-03-12  4:41 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-11  5:39 Thunderbolt, direct-complete and long suspend/resume time of Suspend-to-idle Kai-Heng Feng
2020-03-11 10:38 ` Mika Westerberg
2020-03-12  4:41   ` Kai-Heng Feng [this message]
2020-03-12  8:15     ` Mika Westerberg
2020-03-12 10:10       ` Kai-Heng Feng
2020-03-12 10:41         ` Mika Westerberg
2020-03-13  5:07           ` Kai-Heng Feng
2020-03-13 11:31             ` Mika Westerberg

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