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

[Jiada Wang]

From: Nick Dyer <nick.d...@itdev.co.uk>

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.d...@itdev.co.uk>
[gdavis: Forward port and fix conflicts.]
Signed-off-by: George G. Davis <george_da...@mentor.com>
[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_w...@mentor.com>
Reviewed-by: Dmitry Osipenko <dig...@gmail.com>
Tested-by: Dmitry Osipenko <dig...@gmail.com>
---
 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