MIPS: SGI-IP22/28: Use PROM for memory detection

EARLY_PRINTK uses ArcWrite (via prom_putchar) on IP22/28, which needs
to not mess up PROMs data structures. ARC PROM gives out a list of
memory chunks, which are used and which are free. This fixes the
problem of not working early printk.

By using XKPHYS spaces more than 256MB memory on Indigo2 R4k machines
is working now, too.

Signed-off-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: linux-mips@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

arch/mips/fw/arc/memory.c

@@ -158,6 +158,10 @@ void __init prom_meminit(void)
 	}
 }
 
+void __weak __init prom_cleanup(void)
+{
+}
+
 void __init prom_free_prom_memory(void)
 {
 	int i;
@@ -169,4 +173,9 @@ void __init prom_free_prom_memory(void)
 		free_init_pages("prom memory",
 			prom_mem_base[i], prom_mem_base[i] + prom_mem_size[i]);
 	}
+	/*
+	 * at this point it isn't safe to call PROM functions
+	 * give platforms a way to do PROM cleanups
+	 */
+	prom_cleanup();
 }