On Thu, Sep 20, 2012 at 10:48 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > On Thu, 20 Sep 2012, Ming Lei wrote: > >> This patch sets hub device's default autosuspend delay as 0 to >> speedup bus suspend, see comments in code for details. > > The explanation in the comments assumes that the only reasons for hubs > to wake up are because of a connect change or a wakeup request from a > child. This is not correct. > > Hubs can also be woken up by the user. Have you tried running lsusb on > a system with several USB devices attached to the same hub and the > autosuspend delay set to 0? It's a mess. Looks no mess, see log below: [ 513.732513] hub 1-1.2:1.0: state 7 ports 4 chg 0000 evt 0008 [ 513.826019] usb 1-1.2.3: link qh256-0001/ee780800 start 6 [1/0 us] [ 513.826141] hub 1-1.2.3:1.0: state 7 ports 4 chg 0000 evt 0000 [ 513.826293] hub 1-1.2.3:1.0: hub_suspend [ 513.826324] usb 1-1.2.3: unlink qh256-0001/ee780800 start 6 [1/0 us] [ 513.842559] usb 1-1.2.3: usb auto-suspend, wakeup 1 [ 513.863067] hub 1-1.2:1.0: hub_suspend [ 513.863128] usb 1-1.2: unlink qh256-0001/ee6c7e00 start 2 [1/0 us] [ 513.873413] usb 1-1.2: usb auto-suspend, wakeup 1 [ 513.894287] hub 1-1:1.0: hub_suspend [ 513.894317] usb 1-1: unlink qh256-0001/eea03dc0 start 1 [1/0 us] [ 513.904357] usb 1-1: usb auto-suspend, wakeup 1 [ 513.925506] hub 1-0:1.0: hub_suspend [ 513.925720] usb usb1: bus auto-suspend, wakeup 1 [ 513.925750] ehci-omap ehci-omap.0: suspend root hub [root@tom-pandaboard 1-1.2]# lsusb Bus 001 Device 002: ID 0424:9514 Standard Microsystems Corp. Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 001 Device 003: ID 0424:ec00 Standard Microsystems Corp. Bus 001 Device 004: ID 05e3:0608 Genesys Logic, Inc. USB-2.0 4-Port HUB Bus 001 Device 007: ID 05e3:0606 Genesys Logic, Inc. USB 2.0 Hub / D-Link DUB-H4 USB 2.0 Hub [root@tom-pandaboard 1-1.2]# lsusb --version lsusb (usbutils) 004 > > I think it would make more sense to set the autosuspend delay to > something more like 50 or 100 ms. Maybe even as low as 20. But 0 > seems too small. IMO, suppose it is a problem, we should try to use 0 to make it working because 'lsusb' is just a tool which isn't involved into actual hub function. I will try to study 'lsusb' to see if there is one problem and try to solve it. Thanks, -- Ming Lei -- 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
