Comment 183 for bug 1166442

mika, I also have the asus TP500LN and this seems to be a different problem to this bug.

Description of bug is mouse does not work at all. Dmesg gives "lost sync at byte 6" messages. Mouse does work with proto=imps parameter but no two-finger functionality. If this is the same with you, after sudo su try
echo 1 > /sys/devices/platform/i8042/serio4/reg_07
(or serioX?)
and see if it fixes the issue.

For at least asus TP500LN a kernel patch is under consideration
https://bugzilla.kernel.org/show_bug.cgi?id=84491
https://www.marc.info/?t=142731893400011
Many thanks to Ulrik de Bie!

Perhaps you can post on bugzilla that it affects TP500LA too.