i2c-powermac: Log errors

Log errors when they happen, otherwise we have no idea what went
wrong.
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Tested-by: Michel Daenzer <michel@daenzer.net>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>

drivers/i2c/busses/i2c-powermac.c

@@ -108,16 +108,25 @@ static s32 i2c_powermac_smbus_xfer(	struct i2c_adapter*	adap,
 	}
 
 	rc = pmac_i2c_open(bus, 0);
-	if (rc)
+	if (rc) {
+		dev_err(&adap->dev, "Failed to open I2C, err %d\n", rc);
 		return rc;
+	}
 
 	rc = pmac_i2c_setmode(bus, mode);
-	if (rc)
+	if (rc) {
+		dev_err(&adap->dev, "Failed to set I2C mode %d, err %d\n",
+			mode, rc);
 		goto bail;
+	}
 
 	rc = pmac_i2c_xfer(bus, addrdir, subsize, subaddr, buf, len);
-	if (rc)
+	if (rc) {
+		dev_err(&adap->dev,
+			"I2C transfer at 0x%02x failed, size %d, err %d\n",
+			addrdir >> 1, size, rc);
 		goto bail;
+	}
 
 	if (size == I2C_SMBUS_WORD_DATA && read) {
 		data->word = ((u16)local[1]) << 8;
@@ -157,12 +166,21 @@ static int i2c_powermac_master_xfer(	struct i2c_adapter *adap,
 		addrdir ^= 1;
 
 	rc = pmac_i2c_open(bus, 0);
-	if (rc)
+	if (rc) {
+		dev_err(&adap->dev, "Failed to open I2C, err %d\n", rc);
 		return rc;
+	}
 	rc = pmac_i2c_setmode(bus, pmac_i2c_mode_std);
-	if (rc)
+	if (rc) {
+		dev_err(&adap->dev, "Failed to set I2C mode %d, err %d\n",
+			pmac_i2c_mode_std, rc);
 		goto bail;
+	}
 	rc = pmac_i2c_xfer(bus, addrdir, 0, 0, msgs->buf, msgs->len);
+	if (rc < 0)
+		dev_err(&adap->dev, "I2C %s 0x%02x failed, err %d\n",
+			addrdir & 1 ? "read from" : "write to", addrdir >> 1,
+			rc);
  bail:
 	pmac_i2c_close(bus);
 	return rc < 0 ? rc : 1;