[PATCH] Input: elantech - fix touchpad state on resume for Lenovo N24

[Jonathan Denose]

The Lenovo N24 on resume becomes stuck in a state where it
sends incorrect packets, causing elantech_packet_check_v4 to fail.
The only way for the device to resume sending the correct packets is for
it to be disabled and then re-enabled.

This change adds a dmi check to trigger this behavior on resume.
Signed-off-by: Jonathan Denose <jdenose@xxxxxxxxxx>
---

 drivers/input/mouse/elantech.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/drivers/input/mouse/elantech.c b/drivers/input/mouse/elantech.c
index 4e38229404b4b..e0f3095b4227e 100644
--- a/drivers/input/mouse/elantech.c
+++ b/drivers/input/mouse/elantech.c
@@ -1476,6 +1476,23 @@ static void elantech_disconnect(struct psmouse *psmouse)
 	psmouse->private = NULL;
 }
 
+/*
+ * Some hw_version 4 models fail to properly activate absolute mode on
+ * resume without going through disable/enable cycle.
+ */
+static const struct dmi_system_id elantech_needs_reenable[] = {
+#if defined(CONFIG_DMI) && defined(CONFIG_X86)
+	{
+		/* Lenovo N24 */
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "81AF"),
+		},
+	},
+#endif
+	{ }
+};
+
 /*
  * Put the touchpad back into absolute mode when reconnecting
  */
@@ -1486,6 +1503,22 @@ static int elantech_reconnect(struct psmouse *psmouse)
 	if (elantech_detect(psmouse, 0))
 		return -1;
 
+	if (dmi_check_system(elantech_needs_reenable)) {
+		int err;
+
+		err = ps2_sendbyte(&psmouse->ps2dev, PSMOUSE_CMD_DISABLE, NULL);
+
+		if (err)
+			psmouse_warn(psmouse, "Failed to deactivate mouse on %s: %d\n",
+					psmouse->ps2dev.serio->phys, err);
+
+		err = ps2_sendbyte(&psmouse->ps2dev, PSMOUSE_CMD_ENABLE, NULL);
+
+		if (err)
+			psmouse_warn(psmouse, "Failed to reactivate mouse on %s: %d\n",
+					psmouse->ps2dev.serio->phys, err);
+	}
+
 	if (elantech_set_absolute_mode(psmouse)) {
 		psmouse_err(psmouse,
 			    "failed to put touchpad back into absolute mode.\n");
-- 
2.45.0.rc0.197.gbae5840b3b-goog