[6.12.107] MSI G63 9SEK - Synaptics touchpad falls back to PS/2, multitouch lost at boot, fixed by delayed protocol write

Good morning/afternoon/evening,

I experienced an issue where my Synaptics touchpad is registered as a 
basic PS/2 device at boot, losing all multitouch functionality 
(two-finger scroll, gestures). Writing "synaptics" to the sysfs protocol 
file a few seconds after boot restores the SynPS/2 extended protocol and 
full functionality.

System:

- Kernel: 6.12.107+deb13-amd64
- Distro: LMDE 7 (Debian 13 based)
- Laptop: MSI G63 9SEK
- i8042: PNP: PS/2 Controller [PNP0303:PS2K,PNP0f13:PS2M] at 0x60,0x64 
irq 1,12
- Fix:
     $ cat /etc/systemd/system/psmouse-reload.service
     [Unit]
     Description=Set psmouse protocol to synaptics
     After=systemd-udev-settle.service

     [Service]
     Type=oneshot
     ExecStart=/bin/sh -c 'for i in 1 2 3 4 5; do echo -n synaptics > 
/sys/bus/serio/devices/serio1/protocol 2>/dev/null && exit 0; sleep 2; done'
     RemainAfterExit=yes

     [Install]
     WantedBy=multi-user.target

- Result:
     $ dmesg | grep -iE 'psmouse|synaptics|serio|i8042'
     [    1.006462] i8042: PNP: PS/2 Controller 
[PNP0303:PS2K,PNP0f13:PS2M] at 0x60,0x64 irq 1,12
     [    1.010384] serio: i8042 KBD port at 0x60,0x64 irq 1
     [    1.010392] serio: i8042 AUX port at 0x60,0x64 irq 12
     [    1.018706] input: AT Translated Set 2 keyboard as 
/devices/platform/i8042/serio0/input/input0
     # psmouse probes at boot, fails the Synaptics handshake, registers 
as plain "PS/2 Synaptics TouchPad" (no multitouch)
     [    2.384949] input: PS/2 Synaptics TouchPad as 
/devices/platform/i8042/serio1/input/input6
     # psmouse-reload service runs after systemd-udev-settle and writes 
synaptics to /sys/bus/serio/devices/serio1/protocol, then re-probes with 
the Synaptics extended protocol, queries coordinates, and registers as 
"SynPS/2 Synaptics TouchPad" (multitouch restored)
     [    8.654815] psmouse serio1: synaptics: queried max coordinates: 
x [..5656], y [..4728]
     [    8.683422] psmouse serio1: synaptics: queried min coordinates: 
x [1284..], y [1128..]
     [    8.739382] psmouse serio1: synaptics: Touchpad model: 1, fw: 
8.2, id: 0x1e2b1, caps: 0xf00323/0x840300/0x26800/0x0, board id: 3163, 
fw id: 2286728
     [    8.775128] input: SynPS/2 Synaptics TouchPad as 
/devices/platform/i8042/serio1/input/input21

The issue is 100% reproducible across reboots. "options psmouse 
proto=synaptics" in modprobe config causes "EINVAL" on module insert. 
The handshake fails at that early stage. A systemd service that retries 
the sysfs write after systemd-udev-settle is a reliable workaround.

This appears to be a timing issue where the touchpad firmware or i8042 
controller is not ready for the Synaptics handshake at the time psmouse 
first probes. A retry with a short delay in the probe path, or a 
something more fancy with initial handshake, would likely resolve this.

Happy to provide additional info if required.


Kind regards,

Cameron Spencer