Comment 36 for bug 1949394

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In , linux.bug.reporting (linux.bug.reporting-linux-kernel-bugs) wrote :

There's been a change! As per Philip Nye's observation reported above, I too got the Elantech trackpad working right after cold power on by disconnecting the laptop power cable (at the laptop end) for precisely 60 seconds, as per stop watch, before powering laptop up to directly boot in Linux (mainline or distribution kernel doesn't really matter in my testing). Then every time trackpad gets initialised (as per dmesg|egrep elantech) and works! Now it has to be precisely 60 or more seconds off power cable; 55 seconds, then it doesn't work.

(My previous observation of 12 hours of power off wasn't disconnecting the laptop power cable just before the power on, because I've always had the power on. As I've proven now, it really needs to be off the power cable for a minute, before direct Linux boot, for trackpad to work. Once trackpad is initialised successfully under Linux, power can be turned on. Of course, this is going to be a problem when eventually the battery dies, but then booting Windows 8 first before Linux should get it going at that time, if assuming the root cause hasn't been identified & fixed/worked-around by then.)

Although I'm no expert, it's however starting to feel like some power management issue (perhaps ACPI) and device initialisation (interrupts etc.) in relation to that, although it's totally limited to Elantech trackpad alone from my observation (i.e., no other device -- be it Ethernet, Wireless, Video (Intel 4600 or Noveau driven GTX860M), key board, sound card, USB ports etc. -- exhibits this quirky behaviour.)

As always, am happy to try any fixes or steps that may be provided. It'd be ideal if this Elantech trackpad can be made to work (although, it might not its fault) with Linux straight after a cold power up, with the power cable plugged in, of course.

Thanks