diff --git a/drivers/bus/intel-ixp4xx-eb.c b/drivers/bus/intel-ixp4xx-eb.c
index a4388440aca7..91db001eb69a 100644
--- a/drivers/bus/intel-ixp4xx-eb.c
+++ b/drivers/bus/intel-ixp4xx-eb.c
@@ -49,7 +49,7 @@
 #define IXP4XX_EXP_SIZE_SHIFT		10
 #define IXP4XX_EXP_CNFG_0		BIT(9) /* Always zero */
 #define IXP43X_EXP_SYNC_INTEL		BIT(8) /* Only on IXP43x */
-#define IXP43X_EXP_EXP_CHIP		BIT(7) /* Only on IXP43x */
+#define IXP43X_EXP_EXP_CHIP		BIT(7) /* Only on IXP43x, dangerous to touch on IXP42x */
 #define IXP4XX_EXP_BYTE_RD16		BIT(6)
 #define IXP4XX_EXP_HRDY_POL		BIT(5) /* Only on IXP42x */
 #define IXP4XX_EXP_MUX_EN		BIT(4)
@@ -57,8 +57,6 @@
 #define IXP4XX_EXP_WORD			BIT(2) /* Always zero */
 #define IXP4XX_EXP_WR_EN		BIT(1)
 #define IXP4XX_EXP_BYTE_EN		BIT(0)
-#define IXP42X_RESERVED			(BIT(30)|IXP4XX_EXP_CNFG_0|BIT(8)|BIT(7)|IXP4XX_EXP_WORD)
-#define IXP43X_RESERVED			(BIT(30)|IXP4XX_EXP_CNFG_0|BIT(5)|IXP4XX_EXP_WORD)
 
 #define IXP4XX_EXP_CNFG0		0x20
 #define IXP4XX_EXP_CNFG0_MEM_MAP	BIT(31)
@@ -252,10 +250,9 @@ static void ixp4xx_exp_setup_chipselect(struct ixp4xx_eb *eb,
 		cs_cfg |= val << IXP4XX_EXP_CYC_TYPE_SHIFT;
 	}
 
-	if (eb->is_42x)
-		cs_cfg &= ~IXP42X_RESERVED;
 	if (eb->is_43x) {
-		cs_cfg &= ~IXP43X_RESERVED;
+		/* Should always be zero */
+		cs_cfg &= ~IXP4XX_EXP_WORD;
 		/*
 		 * This bit for Intel strata flash is currently unused, but let's
 		 * report it if we find one.