On Fri, 15 Aug 2014, Du, ChangbinX wrote: > Hi, All, > As described in runtime_pm.txt for pm_wq: > The power management work queue pm_wq in which bus types and device > drivers can put their PM-related work items. It is strongly recommended that > pm_wq be used for queuing all work items related to runtime PM, because > this allows them to be synchronized with system-wide power transitions > (suspend to RAM, hibernation and resume from system sleep states). > > Per my understanding, all runtime PM related works items queued on pm_wq > should be completed before suspend to RAM. So to ensure device state is > runtime active before suspending. Having checked the pm code, I found this is > not true for work items queued by drivers. > > Now usb driver has used this pm_wq to run a work item that resumes root hub > (see function xhci_resume()->usb_hcd_resume_root_hub()). But sometimes > this work is not completed before usb device suspend. That is to say root hub > device may still in runtime suspend state before suspending. And this can result > in problem. One case is that as below error log shows, > > [ 108.046248] PM: Entering mem sleep > [ 108.050487] Suspending console(s) (use no_console_suspend to debug) > [ 108.426510] active wakeup source: event5-576 > [ 108.426529] PM: Some devices failed to suspend > [ 108.426887] dpm_run_callback(): usb_dev_resume+0x0/0x20 returns -113 > [ 108.426918] PM: Device 1-2 failed to resume async: error -113 > [ 108.428299] PM: resume of devices complete after 1.755 msecs > > The usb_dev_resume() return error -113, which mean host is in suspend state > when resuming a device. The scenario is: > 1) Just before system suspending, pm core will run hcd runtime resume > routine if host is in runtime suspend state. > 2) Hcd runtime resume function xhci_resume() returns, and roothub resume > worker was queued by usb_hcd_resume_root_hub(). > 3) system suspend continue going before roothub resume worker starts executing. > Thus host is still in runtime suspend state. > 4) One event make suspending process aborted before hcd suspended. Then pm > core will call resume routines for just suspended device. But when resuming > a usb device it find the host is in suspended. Then return error -113. > > If my analysis is correct, could you share your ideas for this issue? Hasn't this already been fixed? See commit d6236f6d1d88 (xhci: Fix runtime suspended xhci from blocking system suspend). Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
