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From: Mika Westerberg <>
To: Kai-Heng Feng <>
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 10:15:09 +0200	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Thu, Mar 12, 2020 at 12:41:08PM +0800, Kai-Heng Feng wrote:
> > 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().

Before doing that..

> >> 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.

.. we should really understand this better because CML-H PCH root ports
and Titan/Alpine Ridge downstream ports all support active link
reporting so instead of the 1000+100ms you should see something like

  1. Wait for the link + 100ms for the root port
  2. Wait for the link + 100ms for the Titan Ridge downstream ports
    (these are run paraller wrt all Titan Ridge downstream ports that have
     something connected)

If there is a TBT device connected then 2. is repeated for it and so on.

So the 1000ms+ is really unexpected. Are you running mainline kernel and
if so, can you share dmesg with CONFIG_PCI_DEBUG=y so we can see the
delays there? Maybe also add some debugging to
pcie_wait_for_link_delay() where it checks for the
!pdev->link_active_reporting and waits for 1100ms.

  reply	other threads:[~2020-03-12  8:15 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
2020-03-12  8:15     ` Mika Westerberg [this message]
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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