ENGR00227890 ts: fix elan touch screen gets no response upon suspend/resume

To reproduce:
1. let system enter suspend mode
2. touch the screen
3. after the system resumes, touch screen does not respond again.

The cause:
The touch screen interrupt is triggered by falling edge. During suspend stage,
once the screen has ever been touched, then the interrupt line will be always
pulled low. Since elan ts chip is always powered on and the interrupt gets no
chance to be handled during suspend stage, the interrupt line can not recover
to high to detect a new one.

Workaround:
Read out the pending data to make the touch screen come back alive.

Signed-off-by: LiGang <b41990@freescale.com>
Signed-off-by: Robby Cai <R63905@freescale.com>

1 files changed, 30 insertions, 0 deletions

diff --git a/drivers/input/touchscreen/elan_ts.c b/drivers/input/touchscreen/elan_ts.c
index 7edd87d6cd1b..90272594d120 100644
--- a/drivers/input/touchscreen/elan_ts.c
+++ b/drivers/input/touchscreen/elan_ts.c
@@ -359,6 +359,33 @@ static const struct i2c_device_id elan_touch_id[] = {
 	{}
 };
 
+static int elan_suspend(struct device *dev)
+{
+	return 0;
+}
+
+static int elan_resume(struct device *dev)
+{
+	uint8_t buf[IDX_PACKET_SIZE] = { 0 };
+
+	if (0 == elan_touch_detect_int_level()) {
+		dev_dbg(dev, "Got touch during suspend period.\n");
+		/*
+		 * if touch screen during suspend, recv and drop the
+		 * data, then touch interrupt pin will return high after
+		 * receving data.
+		 */
+		elan_touch_recv_data(elan_touch_data.client, buf);
+	}
+
+	return 0;
+}
+
+static const struct dev_pm_ops elan_dev_pm_ops = {
+	.suspend = elan_suspend,
+	.resume  = elan_resume,
+};
+
 static struct i2c_driver elan_touch_driver = {
 	.probe = elan_touch_probe,
 	.remove = elan_touch_remove,
@@ -366,6 +393,9 @@ static struct i2c_driver elan_touch_driver = {
 	.driver = {
 		   .name = "elan-touch",
 		   .owner = THIS_MODULE,
+#ifdef CONFIG_PM
+		   .pm = &elan_dev_pm_ops,
+#endif
 		   },
 };