EDAC, altera: Check parent status for Arria10 EDAC block

In preparation for the Arria10 ECC modules, check the status of the
parent in the device tree to ensure the block is enabled. Skip if no
parent phandle is set in the device tree.

Signed-off-by: Thor Thayer <tthayer@opensource.altera.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-edac <linux-edac@vger.kernel.org>
Link: http://lkml.kernel.org/r/1466603939-7526-2-git-send-email-tthayer@opensource.altera.com
Signed-off-by: Borislav Petkov <bp@suse.de>

drivers/edac/altera_edac.c

@@ -1125,6 +1125,20 @@ static void altr_edac_a10_irq_handler(struct irq_desc *desc)
 	chained_irq_exit(chip, desc);
 }
 
+static int validate_parent_available(struct device_node *np)
+{
+	struct device_node *parent;
+	int ret = 0;
+
+	/* Ensure parent device is enabled if parent node exists */
+	parent = of_parse_phandle(np, "altr,ecc-parent", 0);
+	if (parent && !of_device_is_available(parent))
+		ret = -ENODEV;
+
+	of_node_put(parent);
+	return ret;
+}
+
 static int altr_edac_a10_device_add(struct altr_arria10_edac *edac,
 				    struct device_node *np)
 {
@@ -1146,6 +1160,9 @@ static int altr_edac_a10_device_add(struct altr_arria10_edac *edac,
 	if (IS_ERR_OR_NULL(prv))
 		return -ENODEV;
 
+	if (validate_parent_available(np))
+		return -ENODEV;
+
 	if (!devres_open_group(edac->dev, altr_edac_a10_device_add, GFP_KERNEL))
 		return -ENOMEM;