[BUG] Elantech trackpoint on Thinkpad loses sync, jumps to edge

[BUG] Elantech trackpoint on Thinkpad loses sync, jumps to edge

[Alex Hofbauer]

On my Thinkpad T14s AMD (but observed on multiple models), the trackpoint sometimes jumps to an edge while being used.

There's a bug report I found and commented on [1] some time ago, but as far as I understood, Bugzilla is not the preferred method of reporting bugs?

Kernel: 5.10.2 (but apparently happens on 5.11.0-rc1 as well).

Firmware ID says PNP: LEN2143 PNP0f13.

Setup at boot:

serio: i8042 KBD port at 0x60,0x64 irq 1
serio: i8042 AUX port at 0x60,0x64 irq 12
psmouse serio1: elantech: assuming hardware version 4 (with firmware version 0x7f3001)
psmouse serio1: elantech: Synaptics capabilities query result 0x90, 0x18, 0x0f.
psmouse serio1: elantech: Elan sample query result 00, 80, c9
psmouse serio1: elantech: Trying to set up SMBus access
psmouse serio1: elantech: SMbus companion is not ready yet
input: ETPS/2 Elantech TrackPoint as /devices/platform/i8042/serio1/input/input8
input: ETPS/2 Elantech Touchpad as /devices/platform/i8042/serio1/input/input6

Various occurrences:

Dec 23 11:54:25 shlep kernel: psmouse serio1: elantech: PS/2 packet [24 80 80 36 00 00]
Dec 23 11:56:16 shlep kernel: psmouse serio1: elantech: PS/2 packet [10 80 80 36 00 00]
Dec 23 11:58:31 shlep kernel: psmouse serio1: Touchpad at isa0060/serio1/input0 lost sync at byte 6
Dec 23 11:58:31 shlep kernel: psmouse serio1: Touchpad at isa0060/serio1/input0 - driver resynced.
Dec 23 12:18:32 shlep kernel: psmouse serio1: Touchpad at isa0060/serio1/input0 lost sync at byte 6
Dec 23 12:18:32 shlep kernel: psmouse serio1: Touchpad at isa0060/serio1/input0 - driver resynced.
Dec 23 12:19:42 shlep kernel: psmouse serio1: elantech: PS/2 packet [10 80 80 36 00 00]
Dec 23 12:27:15 shlep kernel: psmouse serio1: Touchpad at isa0060/serio1/input0 lost sync at byte 6
Dec 23 12:27:15 shlep kernel: psmouse serio1: Touchpad at isa0060/serio1/input0 - driver resynced.
Dec 23 12:40:28 shlep kernel: psmouse serio1: elantech: PS/2 packet [34 80 80 36 00 00]
Dec 23 12:41:06 shlep kernel: psmouse serio1: Touchpad at isa0060/serio1/input0 lost sync at byte 6
Dec 23 12:41:06 shlep kernel: psmouse serio1: Touchpad at isa0060/serio1/input0 - driver resynced.
Dec 23 12:44:54 shlep kernel: psmouse serio1: Touchpad at isa0060/serio1/input0 lost sync at byte 6
Dec 23 12:44:54 shlep kernel: psmouse serio1: Touchpad at isa0060/serio1/input0 lost sync at byte 6
Dec 23 12:44:54 shlep kernel: psmouse serio1: Touchpad at isa0060/serio1/input0 lost sync at byte 6
Dec 23 12:44:54 shlep kernel: psmouse serio1: Touchpad at isa0060/serio1/input0 lost sync at byte 6
Dec 23 12:44:54 shlep kernel: psmouse serio1: Touchpad at isa0060/serio1/input0 lost sync at byte 6
Dec 23 12:44:54 shlep kernel: psmouse serio1: issuing reconnect request
Dec 23 12:47:47 shlep kernel: psmouse serio1: Touchpad at isa0060/serio1/input0 lost sync at byte 6
Dec 23 12:47:47 shlep kernel: psmouse serio1: Touchpad at isa0060/serio1/input0 - driver resynced.
Dec 23 13:02:48 shlep kernel: psmouse serio1: Touchpad at isa0060/serio1/input0 lost sync at byte 6
Dec 23 13:02:48 shlep kernel: psmouse serio1: Touchpad at isa0060/serio1/input0 - driver resynced.

/proc/input/devices:

I: Bus=0011 Vendor=0002 Product=000e Version=0000
N: Name="ETPS/2 Elantech TrackPoint"
P: Phys=isa0060/serio1/input1
S: Sysfs=/devices/platform/i8042/serio1/input/input8
U: Uniq=
H: Handlers=mouse0 event6 
B: PROP=21
B: EV=7
B: KEY=70000 0 0 0 0
B: REL=3

I: Bus=0011 Vendor=0002 Product=000e Version=0000
N: Name="ETPS/2 Elantech Touchpad"
P: Phys=isa0060/serio1/input0
S: Sysfs=/devices/platform/i8042/serio1/input/input6
U: Uniq=
H: Handlers=mouse1 event7 
B: PROP=5
B: EV=b
B: KEY=e420 10000 0 0 0 0
B: ABS=661800011000003


All the best,
Alex

[1] https://bugzilla.kernel.org/show_bug.cgi?id=209167