ahci: use pci_alloc_irq_vectors

Use the new pci_alloc_irq_vectors API to allocate MSI-X and MSI vectors.
The big advantage over the old code is that we can use the same API for
MSI and MSI-X, and that we don't need to store the MSI-X vector mapping
in driver-private data structures.

This first conversion keeps the probe order as-is: MSI-X multi vector,
MSI multi vector, MSI single vector, MSI-X single vector and last a
single least legacy interrupt line.  There is one small change of
behavior: we now check the "MSI Revert to Single Message" flag for
MSI-X in addition to MSI.

Because the API to find the Linux IRQ number for a MSI/MSI-X vector
is PCI specific, but libahaci is bus-agnostic I had to a
get_irq_vector function pointer to struct ahci_host_priv.  The
alternative would be to move the multi-vector case of ahci_host_activate
to ahci.c and just call ata_host_activate directly from the others
users of ahci_host_activate.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
index 5a1329e..0d028ea 100644
--- a/drivers/ata/libahci.c
+++ b/drivers/ata/libahci.c
@@ -2378,7 +2378,7 @@
 	/*
 	 * Switch to per-port locking in case each port has its own MSI vector.
 	 */
-	if (hpriv->flags & (AHCI_HFLAG_MULTI_MSI | AHCI_HFLAG_MULTI_MSIX)) {
+	if (hpriv->flags & AHCI_HFLAG_MULTI_MSI) {
 		spin_lock_init(&pp->lock);
 		ap->lock = &pp->lock;
 	}
@@ -2520,7 +2520,7 @@
 	 */
 	for (i = 0; i < host->n_ports; i++) {
 		struct ahci_port_priv *pp = host->ports[i]->private_data;
-		int irq = ahci_irq_vector(hpriv, i);
+		int irq = hpriv->get_irq_vector(host, i);
 
 		/* Do not receive interrupts sent by dummy ports */
 		if (!pp) {
@@ -2556,10 +2556,15 @@
 	int irq = hpriv->irq;
 	int rc;
 
-	if (hpriv->flags & (AHCI_HFLAG_MULTI_MSI | AHCI_HFLAG_MULTI_MSIX)) {
+	if (hpriv->flags & AHCI_HFLAG_MULTI_MSI) {
 		if (hpriv->irq_handler)
 			dev_warn(host->dev,
 			         "both AHCI_HFLAG_MULTI_MSI flag set and custom irq handler implemented\n");
+		if (!hpriv->get_irq_vector) {
+			dev_err(host->dev,
+				"AHCI_HFLAG_MULTI_MSI requires ->get_irq_vector!\n");
+			return -EIO;
+		}
 
 		rc = ahci_host_activate_multi_irqs(host, sht);
 	} else {