of/base: Fix PowerPC address parsing hack

commit 746c9e9f upstream.

We have a historical hack that treats missing ranges properties as the
equivalent of an empty one. This is needed for ancient PowerMac "bad"
device-trees, and shouldn't be enabled for any other PowerPC platform,
otherwise we get some nasty layout of devices in sysfs or even
duplication when a set of otherwise identically named devices is
created multiple times under a different parent node with no ranges
property.

This fix is needed for the PowerNV i2c busses to be exposed properly
and will fix a number of other embedded cases.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Grant Likely <grant.likely@linaro.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

drivers/of/address.c

@@ -403,6 +403,21 @@ static struct of_bus *of_match_bus(struct device_node *np)
 	return NULL;
 }
 
+static int of_empty_ranges_quirk(void)
+{
+	if (IS_ENABLED(CONFIG_PPC)) {
+		/* To save cycles, we cache the result */
+		static int quirk_state = -1;
+
+		if (quirk_state < 0)
+			quirk_state =
+				of_machine_is_compatible("Power Macintosh") ||
+				of_machine_is_compatible("MacRISC");
+		return quirk_state;
+	}
+	return false;
+}
+
 static int of_translate_one(struct device_node *parent, struct of_bus *bus,
 			    struct of_bus *pbus, __be32 *addr,
 			    int na, int ns, int pna, const char *rprop)
@@ -428,12 +443,10 @@ static int of_translate_one(struct device_node *parent, struct of_bus *bus,
 	 * This code is only enabled on powerpc. --gcl
 	 */
 	ranges = of_get_property(parent, rprop, &rlen);
-#if !defined(CONFIG_PPC)
-	if (ranges == NULL) {
+	if (ranges == NULL && !of_empty_ranges_quirk()) {
 		pr_err("OF: no ranges; cannot translate\n");
 		return 1;
 	}
-#endif /* !defined(CONFIG_PPC) */
 	if (ranges == NULL || rlen == 0) {
 		offset = of_read_number(addr, na);
 		memset(addr, 0, pna * 4);