i2c: rcar: disable PM in multi-master mode

In multi master mode, the IP core needs to be always active for
arbitration reasons. Get the config from DT and set up PM depending on
the config.
Acked-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: NWolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: NWolfram Sang <wsa@the-dreams.de>

drivers/i2c/busses/i2c-rcar.c

@@ -96,6 +96,9 @@
 #define ID_DONE		(1 << 2)
 #define ID_ARBLOST	(1 << 3)
 #define ID_NACK		(1 << 4)
+/* persistent flags */
+#define ID_P_PM_BLOCKED	(1 << 31)
+#define ID_P_MASK	ID_P_PM_BLOCKED
 
 enum rcar_i2c_type {
 	I2C_RCAR_GEN1,
@@ -277,7 +280,7 @@ static void rcar_i2c_next_msg(struct rcar_i2c_priv *priv)
 {
 	priv->msg++;
 	priv->msgs_left--;
-	priv->flags = 0;
+	priv->flags &= ID_P_MASK;
 	rcar_i2c_prepare_msg(priv);
 }
 
@@ -495,7 +498,7 @@ static int rcar_i2c_master_xfer(struct i2c_adapter *adap,
 	/* init first message */
 	priv->msg = msgs;
 	priv->msgs_left = num;
-	priv->flags = ID_FIRST_MSG;
+	priv->flags = (priv->flags & ID_P_MASK) | ID_FIRST_MSG;
 	rcar_i2c_prepare_msg(priv);
 
 	time_left = wait_event_timeout(priv->wait, priv->flags & ID_DONE,
@@ -630,7 +633,13 @@ static int rcar_i2c_probe(struct platform_device *pdev)
 		goto out_pm_put;
 
 	rcar_i2c_init(priv);
-	pm_runtime_put(dev);
+
+	/* Don't suspend when multi-master to keep arbitration working */
+	if (of_property_read_bool(dev->of_node, "multi-master"))
+		priv->flags |= ID_P_PM_BLOCKED;
+	else
+		pm_runtime_put(dev);
+
 
 	irq = platform_get_irq(pdev, 0);
 	ret = devm_request_irq(dev, irq, rcar_i2c_irq, 0, dev_name(dev), priv);
@@ -664,6 +673,8 @@ static int rcar_i2c_remove(struct platform_device *pdev)
 	struct device *dev = &pdev->dev;
 
 	i2c_del_adapter(&priv->adap);
+	if (priv->flags & ID_P_PM_BLOCKED)
+		pm_runtime_put(dev);
 	pm_runtime_disable(dev);
 
 	return 0;