On 06/28/2013 10:06 PM, Alan Stern wrote: > On Fri, 28 Jun 2013, Roger Quadros wrote: > >>> That's not what I meant. Never mind the pinctrl; I was asking about >>> the EHCI controller itself. Under what circumstances does the >>> controller assert its wakeup signal? And how do you tell it to stop >>> asserting that signal? >> >> I believe this would be through the EHCI Interrupt enable register (USBINTR). >> I'm not aware of any other mechanism. > > That's strange, because ehci_suspend() sets the intr_enable register to > 0. So how do you ever get any wakeup interrupts at all? Because after ehci_suspend() for OMAP, we solely rely on the out of band wake up mechanism. i.e. Pad wakeup. > >> Right. It seems the external hub has signaled remote wakeup but the kernel doesn't >> resume the root hub's port it is connected to. >> >> By observing the detailed logs below you can see that the root hub does not generate >> an INTerrupt transaction to notify the port status change event. I've captured the pstatus >> and GetPortStatus info as well. > > We don't need an interrupt. The driver is supposed to detect the > remote wakeup sent by the external hub all by itself. OK. Then it could point to a bug in our stack. > >> Failing case >> ------------ >> >> [ 16.108032] usb usb1: usb auto-resume >> [ 16.108062] ehci-omap 48064800.ehci: resume root hub >> [ 16.108154] hub 1-0:1.0: hub_resume >> [ 16.108398] ehci_hub_control GetPortStatus, port 1 temp = 0x1000 >> [ 16.108459] ehci_hub_control GetPortStatus, port 2 temp = 0x14c5 > > Here's where we should detect it. Look at the GetPortStatus case in > ehci_hub_control(); the PORT_RESUME bit (0x0040) is set in temp, so the > "Remote Wakeup received?" code should run. In particular, these lines > should run: > > /* resume signaling for 20 msec */ > ehci->reset_done[wIndex] = jiffies > + msecs_to_jiffies(20); > usb_hcd_start_port_resume(&hcd->self, wIndex); > /* check the port again */ > mod_timer(&ehci_to_hcd(ehci)->rh_timer, > ehci->reset_done[wIndex]); > > Therefore 20 ms later, around timestamp 16.128459, > ehci_hub_status_data() should have been called. At that time, the > root-hub port should have been fully resumed. OK. right. > >> [ 16.108551] hub 1-0:1.0: port 2: status 0507 change 0000 >> [ 16.108612] ehci_hub_control GetPortStatus, port 3 temp = 0x1000 >> [ 16.108642] hub 1-0:1.0: hub_activate submitting urb >> [ 16.109222] ehci_irq port 3 pstatus 0x1000 >> [ 16.109222] ehci_irq port 2 pstatus 0x14c5 >> [ 16.109252] ehci_irq port 1 pstatus 0x1000 >> [ 16.109374] hub 1-0:1.0: state 7 ports 3 chg 0000 evt 0000 > > But apparently nothing happened. Why not? Did the rh_timer get reset? > Maybe you can find out what went wrong. > Sure. I'll investigate. > (Hmmm, we seem to be missing a > > set_bit(wIndex, &ehci->resuming_ports); > > line in there...) > >>> Also, why do you need omap->initialized? Do you think you might get a >>> wakeup interrupt before the controller has been fully set up? I don't >>> see how you could, given the pm_runtime_get_sync() call in the probe >>> routine. >>> >> >> During probe we need to runtime_resume the device before usb_add_hcd() since the >> controller clocks must be enabled before any registers are accessed. >> However, we cannot call ehci_resume() before usb_add_hcd(). So to prevent this >> chicken & egg situation, I've used the omap->initialized flag. It only indicates that >> the ehci structures are initialized and we can call ehci_resume/suspend(). > > Ah, yes. Other subsystems, such as PCI, face exactly the same problem. > > You probably shouldn't call it "initialized", though, because the same > issue arises in ehci_hcd_omap_remove() -- the pm_runtime_put_sync() > there would end up calling ehci_suspend() after usb_remove_hcd(). > "bound" or "started" would be better names. > OK. Started seems fine. cheers, -roger -- 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
