scsi: qla2xxx: Add host attribute to trigger MPI hang

Add a mechanism to trigger MPI pause for debugging purposes.

Link: https://lore.kernel.org/r/20210810043720.1137-2-njavali@marvell.comReviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Arun Easi <aeasi@marvell.com>
Signed-off-by: Nilesh Javali <njavali@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/qla2xxx/qla_attr.c

@@ -1887,6 +1887,30 @@ qla2x00_port_speed_show(struct device *dev, struct device_attribute *attr,
 	return scnprintf(buf, PAGE_SIZE, "%s\n", spd[ha->link_data_rate]);
 }
 
+static ssize_t
+qla2x00_mpi_pause_store(struct device *dev,
+	struct device_attribute *attr, const char *buf, size_t count)
+{
+	scsi_qla_host_t *vha = shost_priv(class_to_shost(dev));
+	int rval = 0;
+
+	if (sscanf(buf, "%d", &rval) != 1)
+		return -EINVAL;
+
+	ql_log(ql_log_warn, vha, 0x7089, "Pausing MPI...\n");
+
+	rval = qla83xx_wr_reg(vha, 0x002012d4, 0x30000001);
+
+	if (rval != QLA_SUCCESS) {
+		ql_log(ql_log_warn, vha, 0x708a, "Unable to pause MPI.\n");
+		count = 0;
+	}
+
+	return count;
+}
+
+static DEVICE_ATTR(mpi_pause, S_IWUSR, NULL, qla2x00_mpi_pause_store);
+
 /* ----- */
 
 static ssize_t
@@ -2482,6 +2506,7 @@ struct device_attribute *qla2x00_host_attrs[] = {
 	&dev_attr_fw_attr,
 	&dev_attr_dport_diagnostics,
 	&dev_attr_edif_doorbell,
+	&dev_attr_mpi_pause,
 	NULL, /* reserve for qlini_mode */
 	NULL, /* reserve for ql2xiniexchg */
 	NULL, /* reserve for ql2xexchoffld */