[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>

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
+

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,