i2c: rcar: bail out on zero length transfers

commit d7653964c590ba846aa11a8f6edf409773cbc492 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
index 4ba4a95b6b2607eda712fa1dcbfea6b4cab3751a..8a806f5c40cf915292d6da7977e6b913d1bc3593 100644 (file)
--- a/drivers/i2c/busses/i2c-rcar.c
+++ b/drivers/i2c/busses/i2c-rcar.c
@@ -541,6 +541,12 @@ 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);
 
@@ -605,7 +611,8 @@ 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 = {