ahci: only try to use multi-MSI mode if there is more than 1 port

We should only try to allocate multiple MSI or MSI-X vectors if the device
actually has multiple ports.  Otherwise pci_alloc_irq_vectors will return
a single vector due to n_ports = 1, in which case we shouldn't set the
AHCI_HFLAG_MULTI_MSI flag.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Fixes: 0b9e2988 ("ahci: use pci_alloc_irq_vectors")
Reported-by: Emmanuel Benisty <benisty.e@gmail.com>
Tested-by: Emmanuel Benisty <benisty.e@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index ba5f11c..ed311a0 100644 (file)
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -1418,21 +1418,24 @@ static int ahci_init_msi(struct pci_dev *pdev, unsigned int n_ports,
         * Message mode could be enforced. In this case assume that advantage
         * of multipe MSIs is negated and use single MSI mode instead.
         */
-       nvec = pci_alloc_irq_vectors(pdev, n_ports, INT_MAX,
-                       PCI_IRQ_MSIX | PCI_IRQ_MSI);
-       if (nvec > 0) {
-               if (!(readl(hpriv->mmio + HOST_CTL) & HOST_MRSM)) {
-                       hpriv->get_irq_vector = ahci_get_irq_vector;
-                       hpriv->flags |= AHCI_HFLAG_MULTI_MSI;
-                       return nvec;
-               }
+       if (n_ports > 1) {
+               nvec = pci_alloc_irq_vectors(pdev, n_ports, INT_MAX,
+                               PCI_IRQ_MSIX | PCI_IRQ_MSI);
+               if (nvec > 0) {
+                       if (!(readl(hpriv->mmio + HOST_CTL) & HOST_MRSM)) {
+                               hpriv->get_irq_vector = ahci_get_irq_vector;
+                               hpriv->flags |= AHCI_HFLAG_MULTI_MSI;
+                               return nvec;
+                       }
 
-               /*
-                * Fallback to single MSI mode if the controller enforced MRSM
-                * mode.
-                */
-               printk(KERN_INFO "ahci: MRSM is on, fallback to single MSI\n");
-               pci_free_irq_vectors(pdev);
+                       /*
+                        * Fallback to single MSI mode if the controller
+                        * enforced MRSM mode.
+                        */
+                       printk(KERN_INFO
+                               "ahci: MRSM is on, fallback to single MSI\n");
+                       pci_free_irq_vectors(pdev);
+               }
        }
 
        /*