of_net: add NVMEM support to of_get_mac_address

Many embedded devices have information such as MAC addresses stored
inside NVMEMs like EEPROMs and so on. Currently there are only two
drivers in the tree which benefit from NVMEM bindings.

Adding support for NVMEM into every other driver would mean adding a lot
of repetitive code. This patch allows us to configure MAC addresses in
various devices like ethernet and wireless adapters directly from
of_get_mac_address, which is already used by almost every driver in the
tree.

Predecessor of this patch which used directly MTD layer has originated
in OpenWrt some time ago and supports already about 497 use cases in 357
device tree files.

Cc: Alban Bedel <albeu@free.fr>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: John Crispin <john@phrozen.org>
Signed-off-by: Petr Štetiar <ynezz@true.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/of/of_net.c

@@ -8,8 +8,10 @@
 #include <linux/etherdevice.h>
 #include <linux/kernel.h>
 #include <linux/of_net.h>
+#include <linux/of_platform.h>
 #include <linux/phy.h>
 #include <linux/export.h>
+#include <linux/device.h>
 
 /**
  * of_get_phy_mode - Get phy mode for given device_node
@@ -47,12 +49,52 @@ static const void *of_get_mac_addr(struct device_node *np, const char *name)
 	return NULL;
 }
 
+static const void *of_get_mac_addr_nvmem(struct device_node *np)
+{
+	int ret;
+	u8 mac[ETH_ALEN];
+	struct property *pp;
+	struct platform_device *pdev = of_find_device_by_node(np);
+
+	if (!pdev)
+		return ERR_PTR(-ENODEV);
+
+	ret = nvmem_get_mac_address(&pdev->dev, &mac);
+	if (ret)
+		return ERR_PTR(ret);
+
+	pp = devm_kzalloc(&pdev->dev, sizeof(*pp), GFP_KERNEL);
+	if (!pp)
+		return ERR_PTR(-ENOMEM);
+
+	pp->name = "nvmem-mac-address";
+	pp->length = ETH_ALEN;
+	pp->value = devm_kmemdup(&pdev->dev, mac, ETH_ALEN, GFP_KERNEL);
+	if (!pp->value) {
+		ret = -ENOMEM;
+		goto free;
+	}
+
+	ret = of_add_property(np, pp);
+	if (ret)
+		goto free;
+
+	return pp->value;
+free:
+	devm_kfree(&pdev->dev, pp->value);
+	devm_kfree(&pdev->dev, pp);
+
+	return ERR_PTR(ret);
+}
+
 /**
  * Search the device tree for the best MAC address to use.  'mac-address' is
  * checked first, because that is supposed to contain to "most recent" MAC
  * address. If that isn't set, then 'local-mac-address' is checked next,
  * because that is the default address. If that isn't set, then the obsolete
- * 'address' is checked, just in case we're using an old device tree.
+ * 'address' is checked, just in case we're using an old device tree. If any
+ * of the above isn't set, then try to get MAC address from nvmem cell named
+ * 'mac-address'.
  *
  * Note that the 'address' property is supposed to contain a virtual address of
  * the register set, but some DTS files have redefined that property to be the
@@ -64,6 +106,8 @@ static const void *of_get_mac_addr(struct device_node *np, const char *name)
  * addresses.  Some older U-Boots only initialized 'local-mac-address'.  In
  * this case, the real MAC is in 'local-mac-address', and 'mac-address' exists
  * but is all zeros.
+ *
+ * Return: Will be a valid pointer on success and ERR_PTR in case of error.
 */
 const void *of_get_mac_address(struct device_node *np)
 {
@@ -77,6 +121,10 @@ const void *of_get_mac_address(struct device_node *np)
 	if (addr)
 		return addr;
 
-	return of_get_mac_addr(np, "address");
+	addr = of_get_mac_addr(np, "address");
+	if (addr)
+		return addr;
+
+	return of_get_mac_addr_nvmem(np);
 }
 EXPORT_SYMBOL(of_get_mac_address);