can: flexcan: Deferred on Regulator return EPROBE_DEFER

commit 555828ef upstream.

Return EPROBE_DEFER if Regulator returns EPROBE_DEFER

If the Flexcan driver is built into kernel and a regulator is used to
enable the CAN transceiver, the Flexcan driver may not use the regulator.

When initializing the Flexcan device with a regulator defined in the device
tree, but not initialized, the regulator subsystem returns EPROBE_DEFER, hence
the Flexcan init fails.

The solution for this is to return EPROBE_DEFER if regulator is not initialized
and wait until the regulator is initialized.
Signed-off-by: Andreas Werner <kernel@andy89.org>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

drivers/net/can/flexcan.c

@@ -1081,12 +1081,19 @@ static int flexcan_probe(struct platform_device *pdev)
 	const struct flexcan_devtype_data *devtype_data;
 	struct net_device *dev;
 	struct flexcan_priv *priv;
+	struct regulator *reg_xceiver;
 	struct resource *mem;
 	struct clk *clk_ipg = NULL, *clk_per = NULL;
 	void __iomem *base;
 	int err, irq;
 	u32 clock_freq = 0;
 
+	reg_xceiver = devm_regulator_get(&pdev->dev, "xceiver");
+	if (PTR_ERR(reg_xceiver) == -EPROBE_DEFER)
+		return -EPROBE_DEFER;
+	else if (IS_ERR(reg_xceiver))
+		reg_xceiver = NULL;
+
 	if (pdev->dev.of_node)
 		of_property_read_u32(pdev->dev.of_node,
 						"clock-frequency", &clock_freq);
@@ -1148,9 +1155,7 @@ static int flexcan_probe(struct platform_device *pdev)
 	priv->pdata = dev_get_platdata(&pdev->dev);
 	priv->devtype_data = devtype_data;
 
-	priv->reg_xceiver = devm_regulator_get(&pdev->dev, "xceiver");
-	if (IS_ERR(priv->reg_xceiver))
-		priv->reg_xceiver = NULL;
+	priv->reg_xceiver = reg_xceiver;
 
 	netif_napi_add(dev, &priv->napi, flexcan_poll, FLEXCAN_NAPI_WEIGHT);