Messages in this thread | | | From | Kai-Heng Feng <> | Subject | Thunderbolt, direct-complete and long suspend/resume time of Suspend-to-idle | Date | Wed, 11 Mar 2020 13:39:51 +0800 |
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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;
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...
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pci/pci.c#n4621 [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/base/power/main.c#n1748
Kai-Heng
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