On Thu, Sep 12, 2024 at 11:21:26AM +0800, duanchenghao wrote: > 在 2024-09-11星期三的 10:40 -0400，Alan Stern写道： > > On Tue, Sep 10, 2024 at 05:36:56PM +0800, duanchenghao wrote: > > > S4 wakeup restores the image that was saved before the system > > > entered > > > the S4 sleep state. > > > > > > S4 waking up from hibernation > > > ============================= > > > kernel initialization > > > | > > > v > > > freeze user task and kernel thread > > > | > > > v > > > load saved image > > > | > > > v > > > freeze the peripheral device and controller > > > (Check the HCD_FLAG_WAKEUP_ PENDING flag of the USB. If it is > > > set, > > > return to EBUSY and do not perform the following restore > > > image.) > > > > Why is the flag set at this point? It should not be; the device and > > controller should have been frozen with wakeup disabled. > > > This is check point, not set point. Yes, I know that. But when the flag was checked, why did the code find that it was set? The flag should have been clear. > > Is your problem related to the one discussed in this email thread? > > > > https://lore.kernel.org/linux-usb/d8600868-6e4b-45ab-b328-852b6ac8ecb5@xxxxxxxxxxxxxxxxxxx/ > > > > Would the suggestion I made there -- i.e., have the xhci-hcd > > interrupt handler skip calling usb_hcd_resume_root_hub() if the root > > hub > > was suspended with wakeup = 0 -- fix your problem? > > Skipping usb_hcd_resume_root_hub() should generally be possible, but > it's important to ensure that normal remote wakeup functionality is not > compromised. Is it HUB_SUSPEND that the hub you are referring to is in > a suspended state? I don't understand this question. hub_quiesce() gets called with HUB_SUSPEND when the hub enters a suspended state. You are correct about the need for normal remote wakeup to work properly. The interrupt handler should skip calling usb_hcd_resume_root_hub() for port connect or disconnect changes and for port overcurrent changes (when the root hub is suspended with wakeup = 0). But it should _not_ skip calling usb_hcd_resume_root_hub() for port resume events. Alan Stern
