wii: use both mem1 and mem2 as ram

The Nintendo Wii video game console has two discontiguous RAM regions:
- MEM1: 24MB @ 0x00000000
- MEM2: 64MB @ 0x10000000

Unfortunately, the kernel currently does not support discontiguous RAM
memory regions on 32-bit PowerPC platforms.

This patch adds a series of workarounds to allow the use of the second
memory region (MEM2) as RAM by the kernel.
Basically, a single range of memory from the beginning of MEM1 to the
end of MEM2 is reported to the kernel, and a memory reservation is
created for the hole between MEM1 and MEM2.

With this patch the system is able to use all the available RAM and not
just ~27% of it.

This will no longer be needed when proper discontig memory support
for 32-bit PowerPC is added to the kernel.

Signed-off-by: Albert Herranz <albert_herranz@yahoo.es>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

arch/powerpc/mm/mmu_decl.h

@@ -136,6 +136,14 @@ extern phys_addr_t total_lowmem;
 extern phys_addr_t memstart_addr;
 extern phys_addr_t lowmem_end_addr;
 
+#ifdef CONFIG_WII
+extern unsigned long wii_hole_start;
+extern unsigned long wii_hole_size;
+
+extern unsigned long wii_mmu_mapin_mem2(unsigned long top);
+extern void wii_memory_fixups(void);
+#endif
+
 /* ...and now those things that may be slightly different between processor
  * architectures.  -- Dan
  */
@@ -155,5 +163,5 @@ extern void adjust_total_lowmem(void);
 #elif defined(CONFIG_PPC32)
 /* anything 32-bit except 4xx or 8xx */
 extern void MMU_init_hw(void);
-extern unsigned long mmu_mapin_ram(void);
+extern unsigned long mmu_mapin_ram(unsigned long top);
 #endif