[PATCH v4 1/1] Input: atmel_mxt_ts - implement I2C retries

[Jiada Wang <jiada_wang@xxxxxxxxxx>]

From: Nick Dyer <nick.dyer@xxxxxxxxxxx>

Some maXTouch chips (eg mXT1386) will not respond on the first I2C request
when they are in a sleep state. It must be retried after a delay for the
chip to wake up.

Signed-off-by: Nick Dyer <nick.dyer@xxxxxxxxxxx>
[gdavis: Forward port and fix conflicts.]
Signed-off-by: George G. Davis <george_davis@xxxxxxxxxx>
[jiada: return exact errno when i2c_transfer & i2c_master_send fails
	rename "retry" to "retried" and keep its order in length
	set "ret" to correct errno before calling dev_err()
	remove reduntant conditional]
Signed-off-by: Jiada Wang <jiada_wang@xxxxxxxxxx>
Reviewed-by: Dmitry Osipenko <digetx@xxxxxxxxx>
Tested-by: Dmitry Osipenko <digetx@xxxxxxxxx>
---
 drivers/input/touchscreen/atmel_mxt_ts.c | 38 ++++++++++++++++--------
 1 file changed, 26 insertions(+), 12 deletions(-)

diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c b/drivers/input/touchscreen/atmel_mxt_ts.c
index a2189739e30f..bad3ac58503d 100644
--- a/drivers/input/touchscreen/atmel_mxt_ts.c
+++ b/drivers/input/touchscreen/atmel_mxt_ts.c
@@ -196,6 +196,7 @@ enum t100_type {
 #define MXT_CRC_TIMEOUT		1000	/* msec */
 #define MXT_FW_RESET_TIME	3000	/* msec */
 #define MXT_FW_CHG_TIMEOUT	300	/* msec */
+#define MXT_WAKEUP_TIME		25	/* msec */
 
 /* Command to unlock bootloader */
 #define MXT_UNLOCK_CMD_MSB	0xaa
@@ -624,6 +625,7 @@ static int __mxt_read_reg(struct i2c_client *client,
 			       u16 reg, u16 len, void *val)
 {
 	struct i2c_msg xfer[2];
+	bool retried = false;
 	u8 buf[2];
 	int ret;
 
@@ -642,22 +644,28 @@ static int __mxt_read_reg(struct i2c_client *client,
 	xfer[1].len = len;
 	xfer[1].buf = val;
 
-	ret = i2c_transfer(client->adapter, xfer, 2);
-	if (ret == 2) {
-		ret = 0;
-	} else {
-		if (ret >= 0)
-			ret = -EIO;
+retry_read:
+	ret = i2c_transfer(client->adapter, xfer, ARRAY_SIZE(xfer));
+	if (ret != ARRAY_SIZE(xfer)) {
+		if (!retried) {
+			dev_dbg(&client->dev, "i2c retry\n");
+			msleep(MXT_WAKEUP_TIME);
+			retried = true;
+			goto retry_read;
+		}
+		ret = ret < 0 ? ret : -EIO;
 		dev_err(&client->dev, "%s: i2c transfer failed (%d)\n",
 			__func__, ret);
+		return ret;
 	}
 
-	return ret;
+	return 0;
 }
 
 static int __mxt_write_reg(struct i2c_client *client, u16 reg, u16 len,
 			   const void *val)
 {
+	bool retried = false;
 	u8 *buf;
 	size_t count;
 	int ret;
@@ -671,14 +679,20 @@ static int __mxt_write_reg(struct i2c_client *client, u16 reg, u16 len,
 	buf[1] = (reg >> 8) & 0xff;
 	memcpy(&buf[2], val, len);
 
+retry_write:
 	ret = i2c_master_send(client, buf, count);
-	if (ret == count) {
-		ret = 0;
-	} else {
-		if (ret >= 0)
-			ret = -EIO;
+	if (ret != count) {
+		if (!retried) {
+			dev_dbg(&client->dev, "i2c retry\n");
+			msleep(MXT_WAKEUP_TIME);
+			retried = true;
+			goto retry_write;
+		}
+		ret = ret < 0 ? ret : -EIO;
 		dev_err(&client->dev, "%s: i2c send failed (%d)\n",
 			__func__, ret);
+	} else {
+		ret = 0;
 	}
 
 	kfree(buf);
-- 
2.17.1