On Tue, 5 May 2015, Lu, Baolu wrote: > The order that software should do during device suspend/resume is > defined in 4.15.1.1 of xHCI spec 1.1. > > Spec 4.15.1.1: > > Software shall stop all endpoints of a device using the Stop Endpoint > Command and setting the Suspend > (SP) flag to �1� prior to selectively suspending a device. But _after_ all the URBs sent to the device have completed, right? > After the > device is resumed software shall ring an > endpoint�s doorbell to restart it. The driver would ring the endpoint's doorbell anyway when a new URB is submitted, wouldn't it? Which means the resume callback doesn't actually have to do anything. > --end-- > > So the order looks like: > > tell hcd device suspend > usb_port_suspend() You have forgotten that usb_port_suspend() can send URBs to the device (to enable remote wakeup, for example). Therefore you shouldn't notify the HCD until usb_port_suspend() is partly or totally finished. > usb_port_resume() > tell hcd device resume You have also forgotten that usb_port_resume() calls various functions that send URBs to ep0 on the device. Therefore if the HCD's device_resume callback needs to do something (like ringing ep0's doorbell), you had better invoke the callback _before_ calling usb_port_resume(). Or maybe you had better do this _within_ usb_port_resume(). 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
