[Dell Inspiron 5552][Synaptics] Touchpad is not working

[Yung Shen]

Install this system with 14.04.3 stock image. Touchpad does not work since installer.
After system upgraded the touchpad still not working.
However it is works in 14.04.1(with kernel 3.3), for the reason why I'm not using 14.04.1 hwe stack please see bug #1502792 comment #4.

$ xinput list
⎡ Virtual core pointer id=2 [master pointer (3)]
⎜ ↳ Virtual core XTEST pointer id=4 [slave pointer (2)]
⎜ ↳ ELAN Touchscreen id=10 [slave pointer (2)]
⎜ ↳ DLLC6D8:00 06CB:796A id=11 [slave pointer (2)]
⎜ ↳ SynPS/2 Synaptics TouchPad id=13 [slave pointer (2)]
⎣ Virtual core keyboard id=3 [master keyboard (2)]
    ↳ Virtual core XTEST keyboard id=5 [slave keyboard (3)]
    ↳ Power Button id=6 [slave keyboard (3)]
    ↳ Video Bus id=7 [slave keyboard (3)]
    ↳ Sleep Button id=8 [slave keyboard (3)]
    ↳ Integrated_Webcam_HD id=9 [slave keyboard (3)]
    ↳ AT Translated Set 2 keyboard id=12 [slave keyboard (3)]
    ↳ Dell WMI hotkeys id=14 [slave keyboard (3)]

$ xinput list-props 13
Device 'SynPS/2 Synaptics TouchPad':
 Device Enabled (139): 1
 Coordinate Transformation Matrix (141): 1.000000, 0.000000, 0.000000, 0.000000, 1.000000, 0.000000, 0.000000, 0.000000, 1.000000
 Device Accel Profile (269): 1
 Device Accel Constant Deceleration (270): 2.500000
 Device Accel Adaptive Deceleration (271): 1.000000
 Device Accel Velocity Scaling (272): 12.500000
 Synaptics Edges (294): 1625, 5359, 1511, 4407
 Synaptics Finger (295): 25, 30, 0
 Synaptics Tap Time (296): 180
 Synaptics Tap Move (297): 241
 Synaptics Tap Durations (298): 180, 180, 100
 Synaptics ClickPad (299): 1
 Synaptics Middle Button Timeout (300): 0
 Synaptics Two-Finger Pressure (301): 282
 Synaptics Two-Finger Width (302): 7
 Synaptics Scrolling Distance (303): 109, 109
 Synaptics Edge Scrolling (304): 0, 0, 0
 Synaptics Two-Finger Scrolling (305): 1, 1
 Synaptics Move Speed (306): 1.000000, 1.750000, 0.036417, 0.000000
 Synaptics Off (307): 2
 Synaptics Locked Drags (308): 0
 Synaptics Locked Drags Timeout (309): 5000
 Synaptics Tap Action (310): 2, 3, 0, 0, 1, 3, 0
 Synaptics Click Action (311): 1, 3, 0
 Synaptics Circular Scrolling (312): 0
 Synaptics Circular Scrolling Distance (313): 0.100000
 Synaptics Circular Scrolling Trigger (314): 0
 Synaptics Circular Pad (315): 0
 Synaptics Palm Detection (316): 0
 Synaptics Palm Dimensions (317): 10, 200
 Synaptics Coasting Speed (318): 20.000000, 50.000000
 Synaptics Pressure Motion (319): 30, 160
 Synaptics Pressure Motion Factor (320): 1.000000, 1.000000
 Synaptics Resolution Detect (321): 1
 Synaptics Grab Event Device (322): 0
 Synaptics Gestures (323): 1
 Synaptics Capabilities (324): 1, 0, 0, 1, 1, 1, 1
 Synaptics Pad Resolution (325): 43, 42
 Synaptics Area (326): 0, 0, 0, 0
 Synaptics Soft Button Areas (327): 3492, 0, 4036, 0, 0, 0, 0, 0
 Synaptics Noise Cancellation (328): 27, 27
 Device Product ID (256): 2, 7
 Device Node (257): "/dev/input/event4"

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: xserver-xorg-input-synaptics-lts-vivid 1.8.1-1ubuntu1~trusty1
ProcVersionSignature: Ubuntu 3.19.0-33.38~14.04.1-generic 3.19.8-ckt7
Uname: Linux 3.19.0-33-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.19
Architecture: amd64
CurrentDesktop: Unity
Date: Thu Nov 19 16:25:10 2015
InstallationDate: Installed on 2015-11-18 (0 days ago)
InstallationMedia: Ubuntu 14.04.3 LTS "Trusty Tahr" - Beta amd64 (20150805)
SourcePackage: xserver-xorg-input-synaptics-lts-vivid
UpgradeStatus: No upgrade log present (probably fresh install)