It's confirmed that it's a Synaptics firmware bug, and the new firmware can fix it. It works for my device, the usb id is 06CB:0AF8 I'm not sure if it'll work or damage other devices, so use it at your own risk.
** Attachment added: "PR1507220.zip" https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-input-evdev/+bug/1180881/+attachment/3835672/+files/PR1507220.zip -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xserver-xorg-input-evdev in Ubuntu. https://bugs.launchpad.net/bugs/1180881 Title: Touchscreen only works after suspend/resume on Lenovo ideapad P400 Touch To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-input-evdev/+bug/1180881/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : ubuntu-x-swat@lists.launchpad.net Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp