[SCSI] megaraid_sas: Add input parameter for max_sectors

Driver add the input parameters support for max_sectors for megaraid
sas gen2 chip.  Customer can set the max_sectors support to 1MB for
gen2 chip during the driver load.

Signed-off-by Bo Yang <bo.yang@lsi.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

drivers/scsi/megaraid/megaraid_sas.c

@@ -56,6 +56,15 @@ module_param_named(poll_mode_io, poll_mode_io, int, 0);
 MODULE_PARM_DESC(poll_mode_io,
 	"Complete cmds from IO path, (default=0)");
 
+/*
+ * Number of sectors per IO command
+ * Will be set in megasas_init_mfi if user does not provide
+ */
+static unsigned int max_sectors;
+module_param_named(max_sectors, max_sectors, int, 0);
+MODULE_PARM_DESC(max_sectors,
+	"Maximum number of sectors per IO command");
+
 MODULE_LICENSE("GPL");
 MODULE_VERSION(MEGASAS_VERSION);
 MODULE_AUTHOR("megaraidlinux@lsi.com");
@@ -3586,6 +3595,27 @@ static int megasas_io_attach(struct megasas_instance *instance)
 			instance->max_fw_cmds - MEGASAS_INT_CMDS;
 	host->this_id = instance->init_id;
 	host->sg_tablesize = instance->max_num_sge;
+	/*
+	 * Check if the module parameter value for max_sectors can be used
+	 */
+	if (max_sectors && max_sectors < instance->max_sectors_per_req)
+		instance->max_sectors_per_req = max_sectors;
+	else {
+		if (max_sectors) {
+			if (((instance->pdev->device ==
+				PCI_DEVICE_ID_LSI_SAS1078GEN2) ||
+				(instance->pdev->device ==
+				PCI_DEVICE_ID_LSI_SAS0079GEN2)) &&
+				(max_sectors <= MEGASAS_MAX_SECTORS)) {
+				instance->max_sectors_per_req = max_sectors;
+			} else {
+			printk(KERN_INFO "megasas: max_sectors should be > 0"
+				"and <= %d (or < 1MB for GEN2 controller)\n",
+				instance->max_sectors_per_req);
+			}
+		}
+	}
+
 	host->max_sectors = instance->max_sectors_per_req;
 	host->cmd_per_lun = 128;
 	host->max_channel = MEGASAS_MAX_CHANNELS - 1;

drivers/scsi/megaraid/megaraid_sas.h

@@ -706,6 +706,7 @@ struct megasas_ctrl_info {
 #define MEGASAS_MAX_LD_IDS			(MEGASAS_MAX_LD_CHANNELS * \
 						MEGASAS_MAX_DEV_PER_CHANNEL)
 
+#define MEGASAS_MAX_SECTORS                    (2*1024)
 #define MEGASAS_DBG_LVL				1
 
 #define MEGASAS_FW_BUSY				1