ThinkPad P14s Gen 2 AMD: Synaptics LEN2073 stuck on PS/2, SMBus companion not ready

[Haris Khan]

Hi,

I have a Lenovo ThinkPad P14s Gen 2 AMD with a Synaptics LEN2073
touchpad, and I appear to be hitting the previously reported
SMBus/RMI4 issue on this platform.

Hardware/system:

Laptop: Lenovo ThinkPad P14s Gen 2 AMD
Touchpad: Synaptics LEN2073
Synaptics board ID: 3471
Current kernel: 7.2.8-1
libinput: 1.32.0

Under Linux the touchpad is detected as:

SynPS/2 Synaptics TouchPad

The PS/2 interface exposes only two multitouch position slots:

ABS_MT_SLOT:
Min 0
Max 1

It can detect additional fingers through BTN_TOOL_TRIPLETAP,
BTN_TOOL_QUADTAP, and BTN_TOOL_QUINTTAP, but only two fingers have
independent positional data.

In practice:

- One-finger tracking works well.
- Two-finger scrolling is smooth.
- Three-finger GNOME workspace/overview gestures are noticeably janky.
- Windows on the same machine provides significantly smoother multitouch
  behavior.

The kernel also reports:

psmouse serio1: synaptics: Your touchpad (PNP: LEN2073 PNP0f13)
says it can support a different bus. If i2c-hid and hid-rmi are not
used, you might want to try setting psmouse.synaptics_intertouch to 1

I have tested:

psmouse.synaptics_intertouch=1

but the RMI/SMBus device does not become available and reports the
previously documented "SMBus companion is not ready yet" condition.

This appears related to the existing P14s Gen 2 AMD reports involving
the AMD FCH i2c-piix4 controller and SMBus Host Notify support.

Previous related discussions:

https://www.spinics.net/lists/linux-input/msg75885.html
https://www.spinics.net/lists/linux-input/msg101577.html

I would like to help determine whether this issue can now be fixed
upstream.

In particular:

1. Is I2C_FUNC_SMBUS_HOST_NOTIFY support for the AMD FCH / i2c-piix4
   controller still the blocker for RMI4/SMBus on this hardware?
2. Is there any current patch series or experimental branch that would
   be useful to test on this P14s Gen 2 AMD?
3. If useful, I am willing to build and test patched kernels and provide
   libinput recordings, dmesg output, PCI information, ACPI tables, or
   other diagnostics.

Relevant current psmouse parameters:

psmouse.proto=auto
psmouse.rate=100
psmouse.resolution=200
psmouse.synaptics_intertouch=-1

Thank you,

Haris Khan