[SCSI] megaraid_sas: Add throttlequeuedepth module parameter

This allows a user to adjust the queue depth of the adapter when throttled due
to I/O timeout.
Signed-off-by: Adam Radford <aradford@gmail.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

drivers/scsi/megaraid/megaraid_sas.h

@@ -747,6 +747,7 @@ struct megasas_ctrl_info {
 #define	MEGASAS_RESET_NOTICE_INTERVAL		5
 #define MEGASAS_IOCTL_CMD			0
 #define MEGASAS_DEFAULT_CMD_TIMEOUT		90
+#define MEGASAS_THROTTLE_QUEUE_DEPTH		16
 
 /*
  * FW reports the maximum of number of commands that it can accept (maximum
@@ -1364,6 +1365,7 @@ struct megasas_instance {
 	unsigned long bar;
 	long reset_flags;
 	struct mutex reset_mutex;
+	int throttlequeuedepth;
 };
 
 enum {

drivers/scsi/megaraid/megaraid_sas_base.c

@@ -71,6 +71,11 @@ static int msix_disable;
 module_param(msix_disable, int, S_IRUGO);
 MODULE_PARM_DESC(msix_disable, "Disable MSI-X interrupt handling. Default: 0");
 
+static int throttlequeuedepth = MEGASAS_THROTTLE_QUEUE_DEPTH;
+module_param(throttlequeuedepth, int, S_IRUGO);
+MODULE_PARM_DESC(throttlequeuedepth,
+	"Adapter queue depth when throttled due to I/O timeout. Default: 16");
+
 MODULE_LICENSE("GPL");
 MODULE_VERSION(MEGASAS_VERSION);
 MODULE_AUTHOR("megaraidlinux@lsi.com");
@@ -1596,7 +1601,8 @@ megasas_check_and_restore_queue_depth(struct megasas_instance *instance)
 	unsigned long flags;
 	if (instance->flag & MEGASAS_FW_BUSY
 	    && time_after(jiffies, instance->last_time + 5 * HZ)
-		&& atomic_read(&instance->fw_outstanding) < 17) {
+	    && atomic_read(&instance->fw_outstanding) <
+	    instance->throttlequeuedepth + 1) {
 
 		spin_lock_irqsave(instance->host->host_lock, flags);
 		instance->flag &= ~MEGASAS_FW_BUSY;
@@ -1914,7 +1920,7 @@ blk_eh_timer_return megasas_reset_timer(struct scsi_cmnd *scmd)
 		/* FW is busy, throttle IO */
 		spin_lock_irqsave(instance->host->host_lock, flags);
 
-		instance->host->can_queue = 16;
+		instance->host->can_queue = instance->throttlequeuedepth;
 		instance->last_time = jiffies;
 		instance->flag |= MEGASAS_FW_BUSY;
 
@@ -3577,6 +3583,24 @@ static int megasas_init_fw(struct megasas_instance *instance)
 
 	kfree(ctrl_info);
 
+	/* Check for valid throttlequeuedepth module parameter */
+	if (instance->pdev->device == PCI_DEVICE_ID_LSI_SAS0073SKINNY ||
+	    instance->pdev->device == PCI_DEVICE_ID_LSI_SAS0071SKINNY) {
+		if (throttlequeuedepth > (instance->max_fw_cmds -
+					  MEGASAS_SKINNY_INT_CMDS))
+			instance->throttlequeuedepth =
+				MEGASAS_THROTTLE_QUEUE_DEPTH;
+		else
+			instance->throttlequeuedepth = throttlequeuedepth;
+	} else {
+		if (throttlequeuedepth > (instance->max_fw_cmds -
+					  MEGASAS_INT_CMDS))
+			instance->throttlequeuedepth =
+				MEGASAS_THROTTLE_QUEUE_DEPTH;
+		else
+			instance->throttlequeuedepth = throttlequeuedepth;
+	}
+
         /*
 	* Setup tasklet for cmd completion
 	*/