On Fri, 11 Nov 2011, Sarah Sharp wrote: > One thing I've been trying to figure out is how device suspend (U3) and > link PM (U1/U2) will interact. One complication is that you can't > directly go from U1 or U2 into U3; instead you have to bring the device > back into U0 and then put it in U3. That means when we suspend a > device, we'll have to disable the device from entering U1 and U2, and > disable the parent hub's port U1/U2 timeouts. Then when we resume a > device we'll have to re-enable the device and hub U1/U2 timeouts. Can you tell the hub to prevent the port from going into U1/U2, or does this require communication with the device? Just curious; I don't think it matters very much. > The bit I'm struggling with that there are places where the USB core > disables autosuspend (like when we're installing to a new configuration) > by calling usb_autoresume_device. Should U1 and U2 be disabled in that > case? Any transfer that's sent will wake up any links in a lower power > state, so I can't really see a need to disable it. Do you? No, I don't think it is necessary. These things aren't time-critical; a little extra delay for the links to power up now and then won't matter. If any drivers really do want to suppress LPM on the paths to their devices, there should be a new API specifically that purpose. 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
