Comment 0 for bug 1854798

environment:
Dell Laptop XPS-9333
Device:
# xinput --list
⎡ Virtual core pointer id=2 [master pointer (3)]
⎜ ↳ Virtual core XTEST pointer id=4 [slave pointer (2)]
⎜ ↳ SYNAPTICS Synaptics Large Touch Screen id=9 [slave pointer (2)]
⎜ ↳ Synaptics s3203 id=12 [slave pointer (2)]
⎜ ↳ Ultrathin Touch Mouse id=11 [slave pointer (2)]
⎣ Virtual core keyboard id=3 [master keyboard (2)]
    ↳ Virtual core XTEST keyboard id=5 [slave keyboard (3)]
    ↳ Dell WMI hotkeys id=13 [slave keyboard (3)]
    ↳ AT Translated Set 2 keyboard id=14 [slave keyboard (3)]
    ↳ Integrated_Webcam_HD: Integrate id=10 [slave keyboard (3)]
    ↳ DELL Wireless hotkeys id=15 [slave keyboard (3)]
    ↳ Video Bus id=7 [slave keyboard (3)]
    ↳ Power Button id=8 [slave keyboard (3)]
    ↳ Power Button id=6 [slave keyboard (3)]

# xinput --list-props 12
Device 'Synaptics s3203':
 Device Enabled (142): 1
 Coordinate Transformation Matrix (144): 1.000000, 0.000000, 0.000000, 0.000000, 1.000000, 0.000000, 0.000000, 0.000000, 1.000000
 Device Accel Profile (270): 1
 Device Accel Constant Deceleration (271): 2.500000
 Device Accel Adaptive Deceleration (272): 1.000000
 Device Accel Velocity Scaling (273): 9.712231
 Synaptics Edges (304): 162, 3908, 133, 2339
 Synaptics Finger (305): 25, 30, 0
 Synaptics Tap Time (306): 180
 Synaptics Tap Move (307): 209
 Synaptics Tap Durations (308): 180, 180, 100
 Synaptics ClickPad (309): 1
 Synaptics Middle Button Timeout (310): 0
 Synaptics Two-Finger Pressure (311): 282
 Synaptics Two-Finger Width (312): 7
 Synaptics Scrolling Distance (313): -95, 95
 Synaptics Edge Scrolling (314): 0, 0, 0
 Synaptics Two-Finger Scrolling (315): 1, 1
 Synaptics Move Speed (316): 1.000000, 1.750000, 0.042008, 0.000000
 Synaptics Off (317): 0
 Synaptics Locked Drags (318): 0
 Synaptics Locked Drags Timeout (319): 5000
 Synaptics Tap Action (320): 0, 0, 0, 0, 1, 3, 2
 Synaptics Click Action (321): 1, 3, 2
 Synaptics Circular Scrolling (322): 0
 Synaptics Circular Scrolling Distance (323): 0.100000
 Synaptics Circular Scrolling Trigger (324): 0
 Synaptics Circular Pad (325): 0
 Synaptics Palm Detection (326): 1
 Synaptics Palm Dimensions (327): 10, 200
 Synaptics Coasting Speed (328): 20.000000, 50.000000
 Synaptics Pressure Motion (329): 30, 160
 Synaptics Pressure Motion Factor (330): 1.000000, 1.000000
 Synaptics Resolution Detect (331): 1
 Synaptics Grab Event Device (332): 0
 Synaptics Gestures (333): 1
 Synaptics Capabilities (334): 1, 0, 0, 1, 1, 1, 0
 Synaptics Pad Resolution (335): 42, 42
 Synaptics Area (336): 0, 0, 0, 0
 Synaptics Soft Button Areas (337): 0, 0, 0, 0, 0, 0, 0, 0
 Synaptics Noise Cancellation (338): 23, 23
 Device Product ID (262): 1739, 10036
 Device Node (263): "/dev/input/event5"

# lspci
00:00.0 Host bridge: Intel Corporation Haswell-ULT DRAM Controller (rev 09)
00:02.0 VGA compatible controller: Intel Corporation Haswell-ULT Integrated Graphics Controller (rev 09)
00:03.0 Audio device: Intel Corporation Haswell-ULT HD Audio Controller (rev 09)
00:14.0 USB controller: Intel Corporation 8 Series USB xHCI HC (rev 04)
00:16.0 Communication controller: Intel Corporation 8 Series HECI #0 (rev 04)
00:1b.0 Audio device: Intel Corporation 8 Series HD Audio Controller (rev 04)
00:1c.0 PCI bridge: Intel Corporation 8 Series PCI Express Root Port 1 (rev e4)
00:1c.2 PCI bridge: Intel Corporation 8 Series PCI Express Root Port 3 (rev e4)
00:1d.0 USB controller: Intel Corporation 8 Series USB EHCI #1 (rev 04)
00:1f.0 ISA bridge: Intel Corporation 8 Series LPC Controller (rev 04)
00:1f.2 SATA controller: Intel Corporation 8 Series SATA Controller 1 [AHCI mode] (rev 04)
00:1f.3 SMBus: Intel Corporation 8 Series SMBus Controller (rev 04)
02:00.0 Network controller: Intel Corporation Wireless 7260 (rev 6b)

# lsusb
Bus 001 Device 002: ID 8087:8000 Intel Corp.
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 003 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 002 Device 004: ID 8087:07dc Intel Corp.
Bus 002 Device 003: ID 1bcf:28ac Sunplus Innovation Technology Inc.
Bus 002 Device 002: ID 06cb:0af8 Synaptics, Inc.
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

# lsmod |grep -i i2
i2c_i801 28672 0
i2c_algo_bit 16384 1 i915
i2c_hid 24576 0
hid 110592 6 i2c_hid,hidp,usbhid,hid_multitouch,hid_generic,hid_rmi

# dmesg |grep -i synaptics
[ 1.977141] usb 2-3: Product: Synaptics Large Touch Screen
[ 1.977142] usb 2-3: Manufacturer: SYNAPTICS
[ 2.111242] rmi4_f01 rmi4-00.fn01: found RMI device, manufacturer: Synaptics, product: s3203, fw id: 1522295
[ 2.175237] input: Synaptics s3203 as /devices/pci0000:00/INT33C3:00/i2c-0/i2c-DLL060A:00/0018:06CB:2734.0001/input/input6
[ 6.196305] input: SYNAPTICS Synaptics Large Touch Screen as /devices/pci0000:00/0000:00:14.0/usb2/2-3/2-3:1.0/0003:06CB:0AF8.0002/input/input17
[ 6.198967] hid-multitouch 0003:06CB:0AF8.0002: input,hiddev0,hidraw1: USB HID v1.11 Mouse [SYNAPTICS Synaptics Large Touch Screen] on usb-0000:00:14.0-3/input0

troubleshooting so far:
1. comment or uncomment /etc/modprobe.d/blacklist.conf blacklist i2c_i801
2. remove xserver-xorg-input-synaptics and install xserver-xorg-input-libinput, and revert back
no result

revert back to kernel 4.15.0-70-generic, touchpad is working

ref:
https://wiki.ubuntu.com/DebuggingTouchpadDetection#generalinfo
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1791921

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: linux-image-4.15.0-72-generic 4.15.0-72.81
ProcVersionSignature: Ubuntu 4.15.0-72.81-generic 4.15.18
Uname: Linux 4.15.0-72-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.9
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC1: lewi 3043 F.... pulseaudio
 /dev/snd/controlC0: lewi 3043 F.... pulseaudio
CurrentDesktop: ubuntu:GNOME
Date: Mon Dec 2 22:30:56 2019
HibernationDevice: RESUME=UUID=006d5f4b-a2fe-4980-a4b6-108756431036
InstallationDate: Installed on 2014-05-10 (2031 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140417)
MachineType: Dell Inc. XPS13 9333
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.15.0-72-generic root=UUID=5bd21a0f-7d69-4ad6-ac73-ad16cc86eb4a ro quiet splash vt.handoff=1
RelatedPackageVersions:
 linux-restricted-modules-4.15.0-72-generic N/A
 linux-backports-modules-4.15.0-72-generic N/A
 linux-firmware 1.173.12
SourcePackage: linux
UpgradeStatus: Upgraded to bionic on 2018-08-12 (476 days ago)
dmi.bios.date: 08/31/2015
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A08
dmi.board.name: 0GFTRT
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 8
dmi.chassis.vendor: Dell Inc.
dmi.chassis.version: 0.1
dmi.modalias: dmi:bvnDellInc.:bvrA08:bd08/31/2015:svnDellInc.:pnXPS139333:pvr:rvnDellInc.:rn0GFTRT:rvrA00:cvnDellInc.:ct8:cvr0.1:
dmi.product.family: Shark Bay System
dmi.product.name: XPS13 9333
dmi.sys.vendor: Dell Inc.