On Fri, 27 Apr 2012, Chen Peter-B29397 wrote: > > No, that's not what I meant. Suppose there is no intermediate hub, > > only a 3G modem plugged directly into the root hub. The 3G modem does > > a runtime autosuspend, and then 2 seconds later sends a wakeup request. > > > > But the autosuspend timeout for the root hub is also 2 seconds, so the > > root hub suspends and the PHY goes into low-power mode at just the same > > time as when the wakeup request arrives. > > At your case, if we put PHY enters low power mode code at both ehci_hub_control > and ehci_bus_suspend, once 3G modem is suspended, the ehci_hub_control > (USB_PORT_FEAT_SUSPEND) will be called, then PHY enters low power mode code > will be called. roohub suspend (ehci_bus_suspend) will not set PORT_SUSPEND > at portsc and call PHY enters low power mode code again. Okay, I didn't realize you wanted to change the PHY state in ehci_hub_control also. You would power-down the PHY whenever every connected port was suspended, right? So consider this scenario instead. There is no intermediate hub, but there are two devices plugged directly into the root hub: a 3G modem and a flash drive. The 3G modem goes into runtime suspend. A minute later, the user unplugs the flash drive, and at that point the PHY is powered down. What's to prevent the modem from sending a wakeup signal at the same time? Are you going to say that this can't happen on the systems you're talking about because their EHCI root hubs have only one port? What about other systems that have more than one port? 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
