diff --git a/drivers/ata/ahci.h b/drivers/ata/ahci.h
index aea30df50c58..b2e0ef4efbdc 100644
--- a/drivers/ata/ahci.h
+++ b/drivers/ata/ahci.h
@@ -386,8 +386,12 @@ struct ahci_host_priv {
 static inline bool ahci_ignore_port(struct ahci_host_priv *hpriv,
 				    unsigned int portid)
 {
-	return portid >= hpriv->nports ||
-		!(hpriv->mask_port_map & (1 << portid));
+	if (portid >= hpriv->nports)
+		return true;
+	/* mask_port_map not set means that all ports are available */
+	if (!hpriv->mask_port_map)
+		return false;
+	return !(hpriv->mask_port_map & (1 << portid));
 }
 
 extern int ahci_ignore_sss;
diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
index fdfa7b266218..e7ace4b10f15 100644
--- a/drivers/ata/libahci.c
+++ b/drivers/ata/libahci.c
@@ -541,6 +541,7 @@ void ahci_save_initial_config(struct device *dev, struct ahci_host_priv *hpriv)
 		hpriv->saved_port_map = port_map;
 	}
 
+	/* mask_port_map not set means that all ports are available */
 	if (hpriv->mask_port_map) {
 		dev_warn(dev, "masking port_map 0x%lx -> 0x%lx\n",
 			port_map,