i2c: rcar: reset controller is mandatory for Gen3+

Initially, we only needed a reset controller to make sure RXDMA works at
least once per transfer. Meanwhile, documentation has been updated. It
now says that a reset has to be performed prior every transaction, even
if it is non-DMA. So, make the reset controller a requirement instead of
being optional. And bail out if resetting fails.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

drivers/i2c/busses/i2c-rcar.c

@@ -838,12 +838,10 @@ static int rcar_i2c_master_xfer(struct i2c_adapter *adap,
 
 	/* Gen3 needs a reset before allowing RXDMA once */
 	if (priv->devtype == I2C_RCAR_GEN3) {
-		priv->flags |= ID_P_NO_RXDMA;
-		if (!IS_ERR(priv->rstc)) {
-			ret = rcar_i2c_do_reset(priv);
-			if (ret == 0)
 		priv->flags &= ~ID_P_NO_RXDMA;
-		}
+		ret = rcar_i2c_do_reset(priv);
+		if (ret)
+			goto out;
 	}
 
 	rcar_i2c_init(priv);
@@ -1094,15 +1092,6 @@ static int rcar_i2c_probe(struct platform_device *pdev)
 		irqhandler = rcar_i2c_gen2_irq;
 	}
 
-	if (priv->devtype == I2C_RCAR_GEN3) {
-		priv->rstc = devm_reset_control_get_exclusive(&pdev->dev, NULL);
-		if (!IS_ERR(priv->rstc)) {
-			ret = reset_control_status(priv->rstc);
-			if (ret < 0)
-				priv->rstc = ERR_PTR(-ENOTSUPP);
-		}
-	}
-
 	/* Stay always active when multi-master to keep arbitration working */
 	if (of_property_read_bool(dev->of_node, "multi-master"))
 		priv->flags |= ID_P_PM_BLOCKED;
@@ -1112,6 +1101,16 @@ static int rcar_i2c_probe(struct platform_device *pdev)
 	if (of_property_read_bool(dev->of_node, "smbus"))
 		priv->flags |= ID_P_HOST_NOTIFY;
 
+	if (priv->devtype == I2C_RCAR_GEN3) {
+		priv->rstc = devm_reset_control_get_exclusive(&pdev->dev, NULL);
+		if (IS_ERR(priv->rstc))
+			goto out_pm_put;
+
+		ret = reset_control_status(priv->rstc);
+		if (ret < 0)
+			goto out_pm_put;
+	}
+
 	ret = platform_get_irq(pdev, 0);
 	if (ret < 0)
 		goto out_pm_put;