[POWERPC] 4xx: 440EPx/GRx incorrect write to DDR SDRAM errata workaround

Add a workaround for PowerPC 440EPx/GRx incorrect write to
DDR SDRAM errata. Data can be written to wrong address
in SDRAM when write pipelining enabled on plb0. We disable
it in the cpu_setup for these processors at early init.

Signed-off-by: Valentine Barshak <vbarshak@ru.mvista.com>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>

2 files changed, 27 insertions, 1 deletions

diff --git a/arch/powerpc/kernel/cpu_setup_44x.S b/arch/powerpc/kernel/cpu_setup_44x.S
index c790634d946b..8e1812e2f3ee 100644
--- a/arch/powerpc/kernel/cpu_setup_44x.S
+++ b/arch/powerpc/kernel/cpu_setup_44x.S
@@ -20,7 +20,14 @@
 _GLOBAL(__setup_cpu_440ep)
         b       __init_fpu_44x
 _GLOBAL(__setup_cpu_440epx)
-        b       __init_fpu_44x
+        mflr    r4
+        bl      __init_fpu_44x
+        bl      __plb_disable_wrp
+        mtlr    r4
+        blr
+_GLOBAL(__setup_cpu_440grx)
+        b       __plb_disable_wrp
+
 
 /* enable APU between CPU and FPU */
 _GLOBAL(__init_fpu_44x)
@@ -31,3 +38,19 @@ _GLOBAL(__init_fpu_44x)
         isync
         blr
 
+/*
+ * Workaround for the incorrect write to DDR SDRAM errata.
+ * The write address can be corrupted during writes to
+ * DDR SDRAM when write pipelining is enabled on PLB0.
+ * Disable write pipelining here.
+ */
+#define DCRN_PLB4A0_ACR 0x81
+
+_GLOBAL(__plb_disable_wrp)
+        mfdcr   r3,DCRN_PLB4A0_ACR
+        /* clear WRP bit in PLB4A0_ACR */
+        rlwinm  r3,r3,0,8,6
+        mtdcr   DCRN_PLB4A0_ACR,r3
+        isync
+        blr
+
diff --git a/arch/powerpc/kernel/cputable.c b/arch/powerpc/kernel/cputable.c
index 94d98190e19a..b03a442b7888 100644
--- a/arch/powerpc/kernel/cputable.c
+++ b/arch/powerpc/kernel/cputable.c
@@ -33,6 +33,7 @@ EXPORT_SYMBOL(cur_cpu_spec);
 #ifdef CONFIG_PPC32
 extern void __setup_cpu_440ep(unsigned long offset, struct cpu_spec* spec);
 extern void __setup_cpu_440epx(unsigned long offset, struct cpu_spec* spec);
+extern void __setup_cpu_440grx(unsigned long offset, struct cpu_spec* spec);
 extern void __setup_cpu_603(unsigned long offset, struct cpu_spec* spec);
 extern void __setup_cpu_604(unsigned long offset, struct cpu_spec* spec);
 extern void __setup_cpu_750(unsigned long offset, struct cpu_spec* spec);
@@ -1146,6 +1147,8 @@ static struct cpu_spec cpu_specs[] = {
                 .cpu_user_features      = COMMON_USER_BOOKE,
                 .icache_bsize           = 32,
                 .dcache_bsize           = 32,
+                .cpu_setup              = __setup_cpu_440grx,
+                .platform               = "ppc440",
         },
         {       /* 440GP Rev. B */
                 .pvr_mask               = 0xf0000fff,