diff --git a/drivers/mfd/axp20x.c b/drivers/mfd/axp20x.c
index 98377d29b783..ed918de84238 100644
--- a/drivers/mfd/axp20x.c
+++ b/drivers/mfd/axp20x.c
@@ -136,6 +136,7 @@ static const struct regmap_range axp806_writeable_ranges[] = {
 	regmap_reg_range(AXP806_PWR_OUT_CTRL1, AXP806_CLDO3_V_CTRL),
 	regmap_reg_range(AXP20X_IRQ1_EN, AXP20X_IRQ2_EN),
 	regmap_reg_range(AXP20X_IRQ1_STATE, AXP20X_IRQ2_STATE),
+	regmap_reg_range(AXP806_REG_ADDR_EXT, AXP806_REG_ADDR_EXT),
 };
 
 static const struct regmap_range axp806_volatile_ranges[] = {
@@ -306,7 +307,7 @@ static const struct regmap_config axp806_regmap_config = {
 	.val_bits	= 8,
 	.wr_table	= &axp806_writeable_table,
 	.volatile_table	= &axp806_volatile_table,
-	.max_register	= AXP806_VREF_TEMP_WARN_L,
+	.max_register	= AXP806_REG_ADDR_EXT,
 	.cache_type	= REGCACHE_RBTREE,
 };
 
diff --git a/include/linux/mfd/axp20x.h b/include/linux/mfd/axp20x.h
index 6349496f09fc..a4860bc9b73d 100644
--- a/include/linux/mfd/axp20x.h
+++ b/include/linux/mfd/axp20x.h
@@ -115,6 +115,8 @@ enum {
 #define AXP806_CLDO2_V_CTRL		0x25
 #define AXP806_CLDO3_V_CTRL		0x26
 #define AXP806_VREF_TEMP_WARN_L		0xf3
+#define AXP806_BUS_ADDR_EXT		0xfe
+#define AXP806_REG_ADDR_EXT		0xff
 
 /* Interrupt */
 #define AXP152_IRQ1_EN			0x40