i2c: rcar: bail out on zero length transfers

This hardware does not support zero length transfers. Instead, the
driver does one (random) byte transfers currently with undefined results
for the slaves. We now bail out.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Cc: stable@kernel.org

diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
index d4fa8eba6e9d2e40e11cb0ccba5ee64606dd8fff..06d47aafbb79c75a18a66e12964544a9a2b3496f 100644 (file)
--- a/drivers/i2c/busses/i2c-rcar.c
+++ b/drivers/i2c/busses/i2c-rcar.c
@@ -561,6 +561,12 @@ static int rcar_i2c_master_xfer(struct i2c_adapter *adap,
 
        ret = -EINVAL;
        for (i = 0; i < num; i++) {
+               /* This HW can't send STOP after address phase */
+               if (msgs[i].len == 0) {
+                       ret = -EOPNOTSUPP;
+                       break;
+               }
+
                /*-------------- spin lock -----------------*/
                spin_lock_irqsave(&priv->lock, flags);
 
@@ -625,7 +631,8 @@ static int rcar_i2c_master_xfer(struct i2c_adapter *adap,
 
 static u32 rcar_i2c_func(struct i2c_adapter *adap)
 {
-       return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+       /* This HW can't do SMBUS_QUICK and NOSTART */
+       return I2C_FUNC_I2C | (I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK);
 }
 
 static const struct i2c_algorithm rcar_i2c_algo = {