[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>

diff --git a/arch/powerpc/kernel/cpu_setup_44x.S b/arch/powerpc/kernel/cpu_setup_44x.S
index c790634..8e1812e 100644 (file)
--- 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 94d9819..b03a442 100644 (file)
--- 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,