sata_sil24: MSI support, disabled by default

The following patch adds MSI support. Some platforms
may have broken MSI, so those are defaulted to use
legacy PCI interrupts.
Signed-off-by: Vivek Mahajan <vivek.mahajan@freescale.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/ata/sata_sil24.c

@@ -417,6 +417,10 @@ static struct ata_port_operations sil24_ops = {
 #endif
 };
 
+static int sata_sil24_msi;    /* Disable MSI */
+module_param_named(msi, sata_sil24_msi, bool, S_IRUGO);
+MODULE_PARM_DESC(msi, "Enable MSI (Default: false)");
+
 /*
  * Use bits 30-31 of port_flags to encode available port numbers.
  * Current maxium is 4.
@@ -1340,6 +1344,11 @@ static int sil24_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 
 	sil24_init_controller(host);
 
+	if (sata_sil24_msi && !pci_enable_msi(pdev)) {
+		dev_printk(KERN_INFO, &pdev->dev, "Using MSI\n");
+		pci_intx(pdev, 0);
+	}
+
 	pci_set_master(pdev);
 	return ata_host_activate(host, pdev->irq, sil24_interrupt, IRQF_SHARED,
 				 &sil24_sht);