ppc: Allow boards to specify effective amount of memory

For historical reasons we limited the stack to 256M because some boards
could only map that much via BATS.  However newer boards are capable of
mapping more memory (for example 85xx is capable of doing up to 2G).

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

lib_ppc/board.c

@@ -361,6 +361,20 @@ init_fnc_t *init_sequence[] = {
 	NULL,			/* Terminate this list */
 };
 
+#ifndef CONFIG_MAX_MEM_MAPPED
+#define CONFIG_MAX_MEM_MAPPED (256 << 20)
+#endif
+ulong get_effective_memsize(void)
+{
+#ifndef	CONFIG_VERY_BIG_RAM
+	return gd->ram_size;
+#else
+	/* limit stack to what we can reasonable map */
+	return ((gd->ram_size > CONFIG_MAX_MEM_MAPPED) ?
+		 CONFIG_MAX_MEM_MAPPED : gd->ram_size);
+#endif
+}
+
 /************************************************************************
  *
  * This is the first part of the initialization sequence that is
@@ -419,13 +433,7 @@ void board_init_f (ulong bootflag)
 	 */
 	len = (ulong)&_end - CFG_MONITOR_BASE;
 
-#ifndef	CONFIG_VERY_BIG_RAM
-	addr = CFG_SDRAM_BASE + gd->ram_size;
-#else
-	/* only allow stack below 256M */
-	addr = CFG_SDRAM_BASE +
-	       (gd->ram_size > 256 << 20) ? 256 << 20 : gd->ram_size;
-#endif
+	addr = CFG_SDRAM_BASE + get_effective_memsize();
 
 #ifdef CONFIG_LOGBUFFER
 	/* reserve kernel log buffer */