On 11 August 2016 at 16:19, Peter Chen <hzpeterchen@xxxxxxxxx> wrote: > On Thu, Aug 11, 2016 at 04:07:21PM +0800, Baolin Wang wrote: >> Hi Peter, >> >> On 11 August 2016 at 14:54, Peter Chen <hzpeterchen@xxxxxxxxx> wrote: >> > On Thu, Aug 11, 2016 at 11:08:52AM +0800, Baolin Wang wrote: >> >> Hi Alan, >> >> >> >> On 10 August 2016 at 22:25, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: >> >> > On Wed, 10 Aug 2016, Baolin Wang wrote: >> >> > >> >> >> >> >> For example: No slave attached----> usb interface runtime suspend >> >> >> >> >> ----> usb device runtime suspend -----> xhci suspend -----> power off >> >> >> >> >> usb controller. After that if the system wants to enter suspend state, >> >> >> >> >> then it also will issue usb_dev_suspend(), then the >> >> >> >> >> pm_runtime_resume() function (issued in choose_wakeup() function) will >> >> >> >> >> return -ESHUTDOWN due to xhci has been suspend and hardware is not >> >> >> >> >> accessible. >> >> >> >> > >> >> >> >> > Why the controller does not be resumed when the root hub has issued >> >> >> >> > runtime resume? >> >> >> >> >> >> >> >> Because now there is no slave attached, we will not power on usb >> >> >> >> controller and resume xhci. >> >> >> >> >> >> >> > >> >> >> > I don't know why you set policy like this. Even the controller is >> >> >> > resumed, it will still be suspended by system suspend. What's more, >> >> >> > if you disallow it, how can you change your wakeup setting? >> >> >> > Eg, at runtime suspend, we enable wakeup by default. But for system >> >> >> > sleep, we disable wakeup by default. >> >> >> > >> >> >> > At runtime, if there is no device on the port, even we resumes the >> >> >> > controller and roohub, it still will be suspended soon. >> >> >> >> >> >> For saving power, if there is no slave attached, why we need to power >> >> >> on usb controller and resume xhci? Especially for mobile device. >> >> > >> >> > You need to power-on the USB controller in order to change the wakeup >> >> > setting. >> >> >> >> pm_runtime_resume() function issued in choose_wakeup() can just resume >> >> usb device, which can not power-on the USB controller and resume xHCI. >> >> Cause the user won't know you need to power-on usb controller now, >> >> then how to power-on the USB controller when changing wakeup setting? >> >> >> >> > >> >> >> Moreover the usb device runtime suspend/resume is separate with xhci >> >> >> suspend/resume, when xhci entered suspend state, only slave attaching >> >> >> can resume xhci. >> >> > >> >> > That's right. Suppose the user wants the system to stay asleep when a >> >> > slave attaches. But when you suspended the xHCI controller, it was set >> >> > to wake up when a new slave attaches. So when a slave is attached, the >> >> > controller will wake up the system. That's bad. >> >> > >> >> > If the wakeup setting needs to be changed when the system suspend >> >> > begins, then you have to power-on the controller to make that change. >> >> > >> >> > Given a choice between using a little power or behaving incorrectly, >> >> > you should choose to use the power. >> >> >> >> OK. But that is a real problem. It will pm_runtime_resume() falied >> >> (issued in choose_wakeup()), cause usb controller has powered-off and >> >> xHCI controller has suspended and we have no method to notify the user >> >> to power-on USB controller. Any good suggestion to solve this, Alan >> >> and Peter? Thanks. >> >> >> > >> > Maybe you can show us the call stack why pm_runtime_resume has failed >> > at your environment. >> >> OK. I try to explain it at below: >> >> For example: No slave attached----> usb interface runtime suspend >> ----> usb device runtime suspend (routine is: >> usb_suspend_device()--->generic_suspend() --> hcd_bus_suspend()--> >> xhci_bus_suspend()) -----> xhci_ suspend() -----> power off usb >> controller. After that if the system wants to enter suspend state, >> then it also will issue usb_dev_suspend(), then the >> pm_runtime_resume() function (issued in choose_wakeup() function) will >> return -ESHUTDOWN due to xhci has been suspend and hardware is not accessible. >> >> We issue the pm_runtime_resume() function routine: usb_resume_device() >> ----> generic_resume() ----> hcd_bus_resume() ---> xhci_bus_resume(), >> but now xHCI is not accessible due to xhci_suspend() is issued and USB >> controller is power off when no slave attached. That is why >> pm_runtime_resume failed. >> > > What host controller driver you are using? Assume you are using > xhci-plat.c. The problem for you is this driver does not implement Yes. I use xhci-plat.c. > runtime pm operations, so the flag HCD_FLAG_HW_ACCESSIBLE is not set. > Maybe Robert's patch is a good start for you [1] > > [1] http://www.spinics.net/lists/linux-usb/msg144602.html OK. Maybe I need to implement the runtime PM callbacks for xhci-plat, right? -- Baolin.wang Best Regards -- 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
