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From: Kai-Heng Feng <>
To: Rafael Wysocki <>,
	Mika Westerberg <>
Cc: "Shih-Yuan Lee (FourDollars)" <>,
	Tiffany <>,
	Linux PCI <>,
	Linux PM <>,
	open list <>
Subject: Thunderbolt, direct-complete and long suspend/resume time of Suspend-to-idle
Date: Wed, 11 Mar 2020 13:39:51 +0800	[thread overview]
Message-ID: <> (raw)


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;

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...



             reply	other threads:[~2020-03-11  5:40 UTC|newest]

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