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[PATCH v2 1/5] MIPS: BCM47XX: ignore last memory page

To: ralf@linux-mips.org, john@phrozen.org
Subject: [PATCH v2 1/5] MIPS: BCM47XX: ignore last memory page
From: Hauke Mehrtens <hauke@hauke-m.de>
Date: Wed, 3 Oct 2012 14:34:16 +0200
Cc: linux-mips@linux-mips.org, Hauke Mehrtens <hauke@hauke-m.de>
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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>
---
 arch/mips/bcm47xx/prom.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/mips/bcm47xx/prom.c b/arch/mips/bcm47xx/prom.c
index f6e9063..22258a4 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);
 }
 
-- 
1.7.9.5


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