Patch is now in mainline. Pending the requisite testing carried out by Ubuntu team, may I please have this patch nominated for promotion to downstream jobs (ie: Xenial, Wily, and Vivid).
Thank you. commit 6fb650d43da3e7054984dc548eaa88765a94d49f Author: Alan Stern <[email protected]> Date: Fri Apr 29 15:25:17 2016 -0400 USB: leave LPM alone if possible when binding/unbinding interface drivers When a USB driver is bound to an interface (either through probing or by claiming it) or is unbound from an interface, the USB core always disables Link Power Management during the transition and then re-enables it afterward. The reason is because the driver might want to prevent hub-initiated link power transitions, in which case the HCD would have to recalculate the various LPM parameters. This recalculation takes place when LPM is re-enabled and the new parameters are sent to the device and its parent hub. However, if the driver does not want to prevent hub-initiated link power transitions then none of this work is necessary. The parameters don't need to be recalculated, and LPM doesn't need to be disabled and re-enabled. It turns out that disabling and enabling LPM can be time-consuming, enough so that it interferes with user programs that want to claim and release interfaces rapidly via usbfs. Since the usbfs kernel driver doesn't set the disable_hub_initiated_lpm flag, we can speed things up and get the user programs to work by leaving LPM alone whenever the flag isn't set. And while we're improving the way disable_hub_initiated_lpm gets used, let's also fix its kerneldoc. Signed-off-by: Alan Stern <[email protected]> Tested-by: Matthew Giassa <[email protected]> CC: Mathias Nyman <[email protected]> CC: <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> ** Patch added: "6fb650d43da3e7054984dc548eaa88765a94d49f.patch" https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1577024/+attachment/4670331/+files/6fb650d43da3e7054984dc548eaa88765a94d49f.patch -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1577024 Title: Kernel 4.2.X and 4.4.X - Fix USB3.0 link power management (LPM) claim/release logic in USBFS To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1577024/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
