openwrt-xburst/target/linux/brcm47xx/patches-2.6.34/170-128MB_ram_bugfix.patch

--- a/arch/mips/bcm47xx/prom.c
+++ b/arch/mips/bcm47xx/prom.c
@@ -126,6 +126,7 @@ static __init void prom_init_cmdline(voi
 static __init void prom_init_mem(void)
 {
 	unsigned long mem;
+	unsigned long max;
 
 	/* Figure out memory size by finding aliases.
 	 *
@@ -134,21 +135,26 @@ static __init void prom_init_mem(void)
 	 * want to reuse the memory used by CFE (around 4MB). That means cfe_*
 	 * functions stop to work at some point during the boot, we should only
 	 * call them at the beginning of the boot.
+	 * 
+	 * BCM47XX uses 128MB for addressing the ram, if the system contains
+	 * less that that amount of ram it remaps the ram more often into the
+	 * available space.
+	 * Accessing memory after 128MB will cause an exception.
+	 * max contains the biggest possible address supported by the platform.
+	 * If the method wants to try something above we assume 128MB ram.
 	 */
+	max = ((unsigned long)(prom_init) | ((128 << 20) - 1));
 	for (mem = (1 << 20); mem < (128 << 20); mem += (1 << 20)) {
+		if (((unsigned long)(prom_init) + mem) > max) {
+			mem = (128 << 20);
+			printk("assume 128MB RAM\n");
+			break;
+		}
 		if (*(unsigned long *)((unsigned long)(prom_init) + mem) ==
 		    *(unsigned long *)(prom_init))
 			break;
 	}
 
-	/* Ignoring the last page when ddr size is 128M. Cached
-	 * accesses to last page is causing the processor to prefetch
-	 * using address above 128M stepping out of the ddr address
-	 * space.
-	 */
-	if (mem == 0x8000000)
-		mem -= 0x1000;
-
 	add_memory_region(0, mem, BOOT_MEM_RAM);
 }