mpt2sas: Added driver module parameter max_msix_vectors

Added driver module parameter max_msix_vectors. Using this
module parameter the maximum number of MSI-X vectors could be set.

The number of MSI-X vectors used would be the minimum of MSI-X vectors
supported by the HBA, the number of CPU cores and the value set to
max_msix_vectors module parameters.

Signed-off-by: Sreekanth Reddy <Sreekanth.Reddy@avagotech.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/scsi/mpt2sas/mpt2sas_base.c

@@ -80,6 +80,10 @@ static int msix_disable = -1;
 module_param(msix_disable, int, 0);
 MODULE_PARM_DESC(msix_disable, " disable msix routed interrupts (default=0)");
 
+static int max_msix_vectors = -1;
+module_param(max_msix_vectors, int, 0);
+MODULE_PARM_DESC(max_msix_vectors, " max msix vectors ");
+
 static int mpt2sas_fwfault_debug;
 MODULE_PARM_DESC(mpt2sas_fwfault_debug, " enable detection of firmware fault "
 	"and halt firmware - (default=0)");
@@ -1402,6 +1406,16 @@ _base_enable_msix(struct MPT2SAS_ADAPTER *ioc)
 	ioc->reply_queue_count = min_t(int, ioc->cpu_count,
 	    ioc->msix_vector_count);
 
+	if (max_msix_vectors > 0) {
+		ioc->reply_queue_count = min_t(int, max_msix_vectors,
+		    ioc->reply_queue_count);
+		ioc->msix_vector_count = ioc->reply_queue_count;
+	}
+
+	printk(MPT2SAS_INFO_FMT
+	"MSI-X vectors supported: %d, no of cores: %d, max_msix_vectors: %d\n",
+	 ioc->name, ioc->msix_vector_count, ioc->cpu_count, max_msix_vectors);
+
 	entries = kcalloc(ioc->reply_queue_count, sizeof(struct msix_entry),
 	    GFP_KERNEL);
 	if (!entries) {