diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index cb1dd5f4988..ed9eb68fd94 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -2587,7 +2587,7 @@ int pcix_get_max_mmrbc(struct pci_dev *dev)
 	if (err)
 		return -EINVAL;
 
-	return (stat & PCI_X_STATUS_MAX_READ) >> 12;
+	return 512 << ((stat & PCI_X_STATUS_MAX_READ) >> 21);
 }
 EXPORT_SYMBOL(pcix_get_max_mmrbc);