ahci: add a module parameter to ignore the SSS flags for async scanning

The SSS flag, which directs the OS to spin up one disk at a time
to not have the PSU blow out, sometimes gets set even when not needed.
The effect of this is a longer-than-needed boot time.

This patch adds a module parameter that makes the driver ignore SSS
at least as far as the parallel scan during boot is concerned...
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/ata/ahci.c

@@ -61,9 +61,14 @@
 #define EM_MSG_LED_VALUE_ON           0x00010000
 
 static int ahci_skip_host_reset;
+static int ahci_ignore_sss;
+
 module_param_named(skip_host_reset, ahci_skip_host_reset, int, 0444);
 MODULE_PARM_DESC(skip_host_reset, "skip global host reset (0=don't skip, 1=skip)");
 
+module_param_named(ignore_sss, ahci_ignore_sss, int, 0444);
+MODULE_PARM_DESC(ignore_sss, "Ignore staggered spinup flag (0=don't ignore, 1=ignore)");
+
 static int ahci_enable_alpm(struct ata_port *ap,
 		enum link_pm policy);
 static void ahci_disable_alpm(struct ata_port *ap);
@@ -2692,8 +2697,10 @@ static int ahci_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 	host->iomap = pcim_iomap_table(pdev);
 	host->private_data = hpriv;
 
-	if (!(hpriv->cap & HOST_CAP_SSS))
+	if (!(hpriv->cap & HOST_CAP_SSS) || ahci_ignore_sss)
 		host->flags |= ATA_HOST_PARALLEL_SCAN;
+	else
+		printk(KERN_INFO "ahci: SSS flag set, parallel bus scan disabled\n");
 
 	if (pi.flags & ATA_FLAG_EM)
 		ahci_reset_em(host);