ARM: pxa: fix mfpr_sync to read from valid offset

Since mfpr_mmio_base[0] is not always valid on later SoCs,
fixed mpfr_sync() to read back from valid mfp offset always.
Signed-off-by: NYu Tang <ytang5@marvell.com>
Signed-off-by: NEric Miao <eric.y.miao@gmail.com>

arch/arm/plat-pxa/mfp.c

@@ -139,10 +139,11 @@ static const unsigned long mfpr_edge[] = {
 #define mfp_configured(p)	((p)->config != -1)
 
 /*
- * perform a read-back of any MFPR register to make sure the
+ * perform a read-back of any valid MFPR register to make sure the
  * previous writings are finished
  */
-#define mfpr_sync()	(void)__raw_readl(mfpr_mmio_base + 0)
+static unsigned long mfpr_off_readback;
+#define mfpr_sync()	(void)__raw_readl(mfpr_mmio_base + mfpr_off_readback)
 
 static inline void __mfp_config_run(struct mfp_pin *p)
 {
@@ -248,6 +249,9 @@ void __init mfp_init_addr(struct mfp_addr_map *map)
 
 	spin_lock_irqsave(&mfp_spin_lock, flags);
 
+	/* mfp offset for readback */
+	mfpr_off_readback = map[0].offset;
+
 	for (p = map; p->start != MFP_PIN_INVALID; p++) {
 		offset = p->offset;
 		i = p->start;