[PATCH] powerpc: Add support for "linux,usable-memory" on memory nodes

Milton has proposed that we should support a "linux,usable-memory" property
on memory nodes which describes, in preference to "reg", the regions of memory
Linux should use.

This facility is required for kdump to inform the second kernel which memory
it should use.

Signed-off-by: Haren Myneni <haren@us.ibm.com>
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/prom.c

@@ -567,7 +567,10 @@ static int __init interpret_root_props(struct device_node *np,
 	unsigned int *rp;
 	int rpsize = (naddrc + nsizec) * sizeof(unsigned int);
 
-	rp = (unsigned int *) get_property(np, "reg", &l);
+	rp = (unsigned int *) get_property(np, "linux,usable-memory", &l);
+	if (rp == NULL)
+		rp = (unsigned int *) get_property(np, "reg", &l);
+
 	if (rp != 0 && l >= rpsize) {
 		i = 0;
 		adr = (struct address_range *) (*mem_start);
@@ -1275,7 +1278,9 @@ static int __init early_init_dt_scan_memory(unsigned long node,
 	} else if (strcmp(type, "memory") != 0)
 		return 0;
 
-	reg = (cell_t *)of_get_flat_dt_prop(node, "reg", &l);
+	reg = (cell_t *)of_get_flat_dt_prop(node, "linux,usable-memory", &l);
+	if (reg == NULL)
+		reg = (cell_t *)of_get_flat_dt_prop(node, "reg", &l);
 	if (reg == NULL)
 		return 0;