Re: [BUG] ThinkPad T490 Synaptics TM3471-020 input lag and missed taps with SMBus/RMI4

[Lovekesh Solanki <lovekeshsolanki00@gmail.com>]

On Tue, Nov 03, 2026 at 04:07:48AM +0000, Eduardo Henrique Teixeira wrote:
> Regarding your questions, I can confirm that the problem persists after
> both warm boots (restarting the laptop) and cold boots (completely shutting
> it down and powering it back on). I haven’t noticed any significant
> difference between these scenarios.
> 
> 
> At first, I suspected some kind of electromagnetic interference or a
> hardware-related issue with the power supply. I even tested a brand-new,
> genuine Lenovo charger that I had kept as a spare, but the behavior
> remained unchanged.
> 
> I believe my initial impression was influenced by how I normally use the
> laptop. I rarely use its built-in touchpad while charging because, at home,
> I usually connect the laptop to a docking station with an external keyboard
> and mouse.
> 
> However, after performing additional tests, I confirmed that the issue
> occurs consistently both while charging and while running on battery power.

Okay, thanks for testing.

> I understand that the original reporter confirmed InterTouch was working
> correctly on their device, so perhaps there is some hardware or firmware
> variation between T490 units that would explain the different results.
> 
> I haven’t yet tested disabling runtime power management specifically, but I
> can perform that test if it would help further investigate the issue.
>

I can't think of any other reason why this only breaks on your machine.
Things look same between the original report and yours.
Maybe Dmitry would have any idea what could cause an issue like this.

Could you also test with runtime PM disabled while rmi4 debug enabled?
(boot via rmi_core.debug_flags=1)
Wonder if the device is getting suspended between touches which might
explain the lag.

Regards,
Lovekesh