Input: synaptics - fix sync lost after resume on some laptops

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

Only the PSMOUSE_CMD_GETID seems to be significant. The
PSMOUSE_CMD_RESET_DIS is irrelevant to this issue after trying
several times.  So we have only implemented this patch to issue
the PSMOUSE_CMD_GETID so far.

Tested-by: Daniel Manrique <daniel.manrique@canonical.com>
Signed-off-by: James M Leddy <james.leddy@canonical.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

diff --git a/drivers/input/mouse/synaptics.c b/drivers/input/mouse/synaptics.c
index 2f78538e09d0f9e733be6f862a4de8e9d2c0301c..b2420ae19e148039147a33081a651d718e8d2e4d 100644 (file)
--- a/drivers/input/mouse/synaptics.c
+++ b/drivers/input/mouse/synaptics.c
@@ -1379,6 +1379,7 @@ static int synaptics_reconnect(struct psmouse *psmouse)
 {
        struct synaptics_data *priv = psmouse->private;
        struct synaptics_data old_priv = *priv;
+       unsigned char param[2];
        int retry = 0;
        int error;
 
@@ -1394,6 +1395,7 @@ static int synaptics_reconnect(struct psmouse *psmouse)
                         */
                        ssleep(1);
                }
+               ps2_command(&psmouse->ps2dev, param, PSMOUSE_CMD_GETID);
                error = synaptics_detect(psmouse, 0);
        } while (error && ++retry < 3);