powerpc: Add memory_hotplug_max()

Add a function to get the maximum address that can be hotplug added.
This is needed to calculate the size of the tce table needed to cover
all memory in 1:1 mode.
Signed-off-by: Milton Miller <miltonm@bga.com>
Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/asm/mmzone.h

@@ -33,6 +33,9 @@ extern int numa_cpu_lookup_table[];
 extern cpumask_var_t node_to_cpumask_map[];
 #ifdef CONFIG_MEMORY_HOTPLUG
 extern unsigned long max_pfn;
+u64 memory_hotplug_max(void);
+#else
+#define memory_hotplug_max() memblock_end_of_DRAM()
 #endif
 
 /*
@@ -42,6 +45,8 @@ extern unsigned long max_pfn;
 #define node_start_pfn(nid)	(NODE_DATA(nid)->node_start_pfn)
 #define node_end_pfn(nid)	(NODE_DATA(nid)->node_end_pfn)
 
+#else
+#define memory_hotplug_max() memblock_end_of_DRAM()
 #endif /* CONFIG_NEED_MULTIPLE_NODES */
 
 #endif /* __KERNEL__ */

arch/powerpc/mm/numa.c

@@ -1247,4 +1247,30 @@ int hot_add_scn_to_nid(unsigned long scn_addr)
 	return nid;
 }
 
+static u64 hot_add_drconf_memory_max(void)
+{
+        struct device_node *memory = NULL;
+        unsigned int drconf_cell_cnt = 0;
+        u64 lmb_size = 0;
+        const u32 *dm = 0;
+
+        memory = of_find_node_by_path("/ibm,dynamic-reconfiguration-memory");
+        if (memory) {
+                drconf_cell_cnt = of_get_drconf_memory(memory, &dm);
+                lmb_size = of_get_lmb_size(memory);
+                of_node_put(memory);
+        }
+        return lmb_size * drconf_cell_cnt;
+}
+
+/*
+ * memory_hotplug_max - return max address of memory that may be added
+ *
+ * This is currently only used on systems that support drconfig memory
+ * hotplug.
+ */
+u64 memory_hotplug_max(void)
+{
+        return max(hot_add_drconf_memory_max(), memblock_end_of_DRAM());
+}
 #endif /* CONFIG_MEMORY_HOTPLUG */