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

Jiada Wang
2020-09-12T01:02:46Z

From: Nick Dyer <nick.dyer@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.dyer@itdev.co.uk>
[gdavis: Forward port and fix conflicts.]
Signed-off-by: George G. Davis <george_davis@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_wang@mentor.com>
Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
Tested-by: Dmitry Osipenko <digetx@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