MIPS: BCM47XX: ignore last memory page

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.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Patchwork: http://patchwork.linux-mips.org/patch/4365
Signed-off-by: John Crispin <blogic@openwrt.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/arch/mips/bcm47xx/prom.c b/arch/mips/bcm47xx/prom.c
index f6e9063cc4c2..22258a4c652b 100644
--- a/arch/mips/bcm47xx/prom.c
+++ b/arch/mips/bcm47xx/prom.c
@@ -27,6 +27,7 @@
 #include <linux/types.h>
 #include <linux/kernel.h>
 #include <linux/spinlock.h>
+#include <linux/smp.h>
 #include <asm/bootinfo.h>
 #include <asm/fw/cfe/cfe_api.h>
 #include <asm/fw/cfe/cfe_error.h>
@@ -127,6 +128,7 @@ static __init void prom_init_mem(void)
 {
         unsigned long mem;
         unsigned long max;
+        struct cpuinfo_mips *c = &current_cpu_data;
 
         /* Figure out memory size by finding aliases.
          *
@@ -155,6 +157,14 @@ static __init void prom_init_mem(void)
                         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 (c->cputype == CPU_74K && (mem == (128  << 20)))
+                mem -= 0x1000;
+
         add_memory_region(0, mem, BOOT_MEM_RAM);
 }