/*The limit of outstanding scsi command that firmware can handle*/
 #define ARCMSR_MAX_FREECCB_NUM         1024
 #define ARCMSR_MAX_OUTSTANDING_CMD     1024
+#define ARCMSR_DEFAULT_OUTSTANDING_CMD 128
+#define ARCMSR_MIN_OUTSTANDING_CMD     32
 #define ARCMSR_DRIVER_VERSION          "v1.30.00.22-20151126"
 #define ARCMSR_SCSI_INITIATOR_ID                                               255
 #define ARCMSR_MAX_XFER_SECTORS                                                        512
 
 MODULE_LICENSE("Dual BSD/GPL");
 MODULE_VERSION(ARCMSR_DRIVER_VERSION);
 
+static int host_can_queue = ARCMSR_DEFAULT_OUTSTANDING_CMD;
+module_param(host_can_queue, int, S_IRUGO);
+MODULE_PARM_DESC(host_can_queue, " adapter queue depth(32 ~ 1024), default is 128");
+
 #define        ARCMSR_SLEEPTIME        10
 #define        ARCMSR_RETRYCOUNT       12
 
        .eh_bus_reset_handler   = arcmsr_bus_reset,
        .bios_param             = arcmsr_bios_param,
        .change_queue_depth     = arcmsr_adjust_disk_queue_depth,
-       .can_queue              = ARCMSR_MAX_OUTSTANDING_CMD,
+       .can_queue              = ARCMSR_DEFAULT_OUTSTANDING_CMD,
        .this_id                        = ARCMSR_SCSI_INITIATOR_ID,
        .sg_tablesize                   = ARCMSR_DEFAULT_SG_ENTRIES, 
        .max_sectors                    = ARCMSR_MAX_XFER_SECTORS_C, 
        host->max_lun = ARCMSR_MAX_TARGETLUN;
        host->max_id = ARCMSR_MAX_TARGETID;             /*16:8*/
        host->max_cmd_len = 16;                         /*this is issue of 64bit LBA ,over 2T byte*/
-       host->can_queue = ARCMSR_MAX_OUTSTANDING_CMD;
+       if ((host_can_queue < ARCMSR_MIN_OUTSTANDING_CMD) || (host_can_queue > ARCMSR_MAX_OUTSTANDING_CMD))
+               host_can_queue = ARCMSR_DEFAULT_OUTSTANDING_CMD;
+       host->can_queue = host_can_queue;       /* max simultaneous cmds */
        host->cmd_per_lun = ARCMSR_MAX_CMD_PERLUN;          
        host->this_id = ARCMSR_SCSI_INITIATOR_ID;
        host->unique_id = (bus << 8) | dev_fun;
        default:
                break;
        }
-       if (acb->firm_numbers_queue > ARCMSR_MAX_OUTSTANDING_CMD)
-               acb->maxOutstanding = ARCMSR_MAX_OUTSTANDING_CMD;
+       acb->maxOutstanding = acb->firm_numbers_queue - 1;
+       if (acb->host->can_queue >= acb->firm_numbers_queue)
+               acb->host->can_queue = acb->maxOutstanding;
        else
-               acb->maxOutstanding = acb->firm_numbers_queue - 1;
-       acb->host->can_queue = acb->maxOutstanding;
+               acb->maxOutstanding = acb->host->can_queue;
        acb->maxFreeCCB = acb->host->can_queue;
        if (acb->maxFreeCCB < ARCMSR_MAX_FREECCB_NUM)
                acb->maxFreeCCB += 64;