Hi Eric,

On Sun, Jun 24, 2012 at 11:32:38PM +0800, Eric Miao wrote:

All,

BugLink: https://bugs.launchpad.net/bugs/717970

So in summary, the symptom is intermittent key events lost after resume
on some machines with synaptics touchpad (seems this is synaptics _only_),
and key events loss is due to serio port reconnect after psmouse sync lost.
Removing psmouse and inserting it back during the suspend/resume process
is able to work around the issue, so the difference between psmouse_connect()
and psmouse_reconnect() is the key to the root cause of this problem.

After comparing the two different paths, synaptics driver has its own
implementation of synaptics_reconnect(), and the missing psmouse_probe()
seems significant, the patch below added psmouse_probe() to the reconnect
process, and has been verified many times that the issue could not be reliably
reproduced.

There are two PS/2 commands in psmouse_probe():

  1. PSMOUSE_CMD_GETID
  2. PSMOUSE_CMD_RESET_DIS

The weird thing is, the PSMOUSE_CMD_GETID seems to be significant, and the
PSMOUSE_CMD_RESET_DIS is irrelevant to this issue after trying several times.
Now it's rather difficult to form a sane theory. So this patch is
really for RFC.

Hmm, murky and unknown to us EC/KBC firmware code and uglies are hidden
there...

I issuing PSMOUSE_CMD_GETID bis fine if it makes some firmware happy and
we probably should do it for all protocols, not only Synaptics. Could
you please try moving calls to psmouse_reset() and psmouse_probe() in
psmouse_reconnect() up, before we check if we have protocol specific
reconnect handler?

Thanks.

-- 
Dmitry