1 files changed, 19 insertions, 16 deletions

diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index 27c8d56111c..29e71bddd6f 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -679,24 +679,20 @@ static void ahci_save_initial_config(struct pci_dev *pdev,
 
 	/* cross check port_map and cap.n_ports */
 	if (port_map) {
-		u32 tmp_port_map = port_map;
-		int n_ports = ahci_nr_ports(cap);
+		int map_ports = 0;
 
-		for (i = 0; i < AHCI_MAX_PORTS && n_ports; i++) {
-			if (tmp_port_map & (1 << i)) {
-				n_ports--;
-				tmp_port_map &= ~(1 << i);
-			}
-		}
+		for (i = 0; i < AHCI_MAX_PORTS; i++)
+			if (port_map & (1 << i))
+				map_ports++;
 
-		/* If n_ports and port_map are inconsistent, whine and
-		 * clear port_map and let it be generated from n_ports.
+		/* If PI has more ports than n_ports, whine, clear
+		 * port_map and let it be generated from n_ports.
 		 */
-		if (n_ports || tmp_port_map) {
+		if (map_ports > ahci_nr_ports(cap)) {
 			dev_printk(KERN_WARNING, &pdev->dev,
-				   "nr_ports (%u) and implemented port map "
-				   "(0x%x) don't match, using nr_ports\n",
-				   ahci_nr_ports(cap), port_map);
+				   "implemented port map (0x%x) contains more "
+				   "ports than nr_ports (%u), using nr_ports\n",
+				   port_map, ahci_nr_ports(cap));
 			port_map = 0;
 		}
 	}
@@ -2201,7 +2197,7 @@ static int ahci_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 	struct device *dev = &pdev->dev;
 	struct ahci_host_priv *hpriv;
 	struct ata_host *host;
-	int i, rc;
+	int n_ports, i, rc;
 
 	VPRINTK("ENTER\n");
 
@@ -2255,7 +2251,14 @@ static int ahci_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 	if (hpriv->cap & HOST_CAP_PMP)
 		pi.flags |= ATA_FLAG_PMP;
 
-	host = ata_host_alloc_pinfo(&pdev->dev, ppi, fls(hpriv->port_map));
+	/* CAP.NP sometimes indicate the index of the last enabled
+	 * port, at other times, that of the last possible port, so
+	 * determining the maximum port number requires looking at
+	 * both CAP.NP and port_map.
+	 */
+	n_ports = max(ahci_nr_ports(hpriv->cap), fls(hpriv->port_map));
+
+	host = ata_host_alloc_pinfo(&pdev->dev, ppi, n_ports);
 	if (!host)
 		return -ENOMEM;
 	host->iomap = pcim_iomap_table(pdev);