powerpc/5xxx: Add common mpc5xxx_get_bus_frequency() function

So far, MPC512x used mpc512x_find_ips_freq() to get the bus frequency,
while MPC52xx used mpc52xx_find_ipb_freq().  Despite the different
clock names (IPS vs. IPB) the code was identical.

Use common code for both processor families.

Signed-off-by: Wolfgang Denk <wd@denx.de>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

arch/powerpc/sysdev/Makefile

@@ -50,6 +50,9 @@ obj-$(CONFIG_PPC_DCR)		+= dcr.o
 obj-$(CONFIG_8xx)		+= mpc8xx_pic.o cpm1.o
 obj-$(CONFIG_UCODE_PATCH)	+= micropatch.o
 
+obj-$(CONFIG_PPC_MPC512x)	+= mpc5xxx_clocks.o
+obj-$(CONFIG_PPC_MPC52xx)	+= mpc5xxx_clocks.o
+
 ifeq ($(CONFIG_SUSPEND),y)
 obj-$(CONFIG_6xx)		+= 6xx-suspend.o
 endif

arch/powerpc/sysdev/mpc5xxx_clocks.c

@@ -0,0 +1,33 @@
+/**
+ * 	mpc5xxx_get_bus_frequency - Find the bus frequency for a device
+ * 	@node:	device node
+ *
+ * 	Returns bus frequency (IPS on MPC512x, IPB on MPC52xx),
+ * 	or 0 if the bus frequency cannot be found.
+ */
+
+#include <linux/kernel.h>
+#include <linux/of_platform.h>
+
+unsigned int
+mpc5xxx_get_bus_frequency(struct device_node *node)
+{
+	struct device_node *np;
+	const unsigned int *p_bus_freq = NULL;
+
+	of_node_get(node);
+	while (node) {
+		p_bus_freq = of_get_property(node, "bus-frequency", NULL);
+		if (p_bus_freq)
+			break;
+
+		np = of_get_parent(node);
+		of_node_put(node);
+		node = np;
+	}
+	if (node)
+		of_node_put(node);
+
+	return p_bus_freq ? *p_bus_freq : 0;
+}
+EXPORT_SYMBOL(mpc5xxx_get_bus_frequency);