[PATCH 2.6.32 v2] MCP55 SATA2 conditional MSI support for sata_nv

[Tony Vroon <tony@linx.net>]

The nVidia MCP55 SATA2 controller quite happily supports MSI.
This adds an option to use it. It is disabled by default and 
will only be honoured on the specific controller I tested.
This was suggested in 2007 back when the driver was less mature, 
perhaps now is a better time for it.

Signed-off-by: Tony Vroon <tony@linx.net>

diff --git a/drivers/ata/sata_nv.c b/drivers/ata/sata_nv.c
index b2d11f3..5ec29c4 100644
--- a/drivers/ata/sata_nv.c
+++ b/drivers/ata/sata_nv.c
@@ -602,6 +602,7 @@ MODULE_VERSION(DRV_VERSION);
 
 static int adma_enabled;
 static int swncq_enabled = 1;
+static int msi_enabled;
 
 static void nv_adma_register_mode(struct ata_port *ap)
 {
@@ -2459,6 +2460,13 @@ static int nv_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 	} else if (type == SWNCQ)
 		nv_swncq_host_init(host);
 
+	/* enable MSI if requested */
+	if (pdev->device == PCI_DEVICE_ID_NVIDIA_NFORCE_MCP55_SATA2 &&
+		msi_enabled) {
+		dev_printk(KERN_NOTICE, &pdev->dev, "Using MSI\n");
+		pci_enable_msi(pdev);
+	}
+
 	pci_set_master(pdev);
 	return ata_host_activate(host, pdev->irq, ipriv->irq_handler,
 				 IRQF_SHARED, ipriv->sht);
@@ -2558,4 +2566,6 @@ module_param_named(adma, adma_enabled, bool, 0444);
 MODULE_PARM_DESC(adma, "Enable use of ADMA (Default: false)");
 module_param_named(swncq, swncq_enabled, bool, 0444);
 MODULE_PARM_DESC(swncq, "Enable use of SWNCQ (Default: true)");
+module_param_named(msi, msi_enabled, bool, 0444);
+MODULE_PARM_DESC(msi, "Enable use of MSI (Default: false)");