On Tue, 17 Apr 2012, Stephen Warren wrote: > Aha, there's a CONFIG_USB_SUSPEND which I didn't have enabled. Now I see > the controller suspending. Good job. I should have thought of that... > However, the controller suspends immediately the system boots even if > there's a device already connected, and never resumes if there wasn't > connected at boot, but one is plugged in later. The general idea is that when usb_add_hcd() registers the root hub, the hub driver prevents the root hub from autosuspending until it has a chance to scan the ports with plugged-in devices. And naturally, the controller won't suspend while the root hub is running. So maybe the root hub doesn't see the connected devices? You can find out by collecting a usbmon trace for bus 0, starting before you load the ehci-hcd module. > In this state, I must set tegra-ehci.2/usb3/power/control=on to get > anything to work. Forcing just the controller on > (tegra-ehci.2/power/control=on) doesn't fix this. Yeah, powering up the controller doesn't necessarily cause the root hub to be powered up too. Of course, if power_down_on_bus_suspend isn't enabled then the controller's power/control is supposed to be set to "on" by default. > After than, I can set tegra-ehci.2/usb3/power/control=auto, and see the > root hub (tegra-ehci.2/usb3/power) suspending/resuming as devices are > unplugged/plugged. > > I just can't have tegra-ehci.2/power/control=auto while nothing is > plugged in, or the cycle starts again. In other words, if both the root hub and the controller are powered down, then neither one wakes up when a device is plugged in? > I assume this a bug in the Tegra EHCI driver's suspend implementation? Actually it sounds like a bug in the controller's wakeup mechanism. Maybe a hardware bug, maybe a software bug. While looking through the code, I didn't notice anything about enabling wakeups. But I wasn't looking very carefully, because I don't know how the Tegra platform works. A quick search through the patch now seems to show that wakeups never get enabled at all! How well does the existing driver work if you enable the power_down_on_bus_suspend flag in the platform data? 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
