diff --git a/src/northbridge/intel/haswell/acpi.c b/src/northbridge/intel/haswell/acpi.c
index 1df66bc..cc4487c 100644
--- a/src/northbridge/intel/haswell/acpi.c
+++ b/src/northbridge/intel/haswell/acpi.c
@@ -2,6 +2,7 @@
 
 #include <types.h>
 #include <console/console.h>
+#include <commonlib/helpers.h>
 #include <acpi/acpi.h>
 #include <device/device.h>
 #include <device/pci_ops.h>
@@ -10,44 +11,12 @@
 
 unsigned long acpi_fill_mcfg(unsigned long current)
 {
-	struct device *dev;
-	u32 pciexbar = 0;
-	u32 pciexbar_reg;
-	int max_buses;
-	u32 mask;
+	u32 length, pciexbar;
 
-	dev = pcidev_on_root(0, 0);
-	if (!dev)
+	if (!decode_pcie_bar(&pciexbar, &length))
 		return current;
 
-	pciexbar_reg = pci_read_config32(dev, PCIEXBAR);
-
-	/* MMCFG not supported or not enabled. */
-	if (!(pciexbar_reg & (1 << 0)))
-		return current;
-
-	mask = (1UL << 31) | (1 << 30) | (1 << 29) | (1 << 28);
-	switch ((pciexbar_reg >> 1) & 3) {
-	case 0: /* 256MB */
-		pciexbar = pciexbar_reg & mask;
-		max_buses = 256;
-		break;
-	case 1: /* 128M */
-		mask |= (1 << 27);
-		pciexbar = pciexbar_reg & mask;
-		max_buses = 128;
-		break;
-	case 2: /* 64M */
-		mask |= (1 << 27) | (1 << 26);
-		pciexbar = pciexbar_reg & mask;
-		max_buses = 64;
-		break;
-	default: /* RSVD */
-		return current;
-	}
-
-	if (!pciexbar)
-		return current;
+	const int max_buses = length / MiB;
 
 	current += acpi_create_mcfg_mmconfig((acpi_mcfg_mmconfig_t *) current, pciexbar, 0, 0,
 					     max_buses - 1);
diff --git a/src/northbridge/intel/haswell/haswell.h b/src/northbridge/intel/haswell/haswell.h
index 5e28336..9a99c2a 100644
--- a/src/northbridge/intel/haswell/haswell.h
+++ b/src/northbridge/intel/haswell/haswell.h
@@ -157,6 +157,8 @@
 
 void report_platform_info(void);
 
+int decode_pcie_bar(u32 *const base, u32 *const len);
+
 #include <device/device.h>
 
 struct acpi_rsdp;
diff --git a/src/northbridge/intel/haswell/northbridge.c b/src/northbridge/intel/haswell/northbridge.c
index 0a5af4f..e1c26d1 100644
--- a/src/northbridge/intel/haswell/northbridge.c
+++ b/src/northbridge/intel/haswell/northbridge.c
@@ -51,6 +51,11 @@
 	return 0;
 }
 
+int decode_pcie_bar(u32 *const base, u32 *const len)
+{
+	return get_pcie_bar(pcidev_on_root(0, 0), PCIEXBAR, base, len);
+}
+
 static const char *northbridge_acpi_name(const struct device *dev)
 {
 	if (dev->path.type == DEVICE_PATH_DOMAIN)