scsi: qla2xxx: use shadow register for ISP27XX

For ISP27XX, use shadow register to read FW provided REQQ's consumer
index.  The shadow register is dma'ed by firmware.
Signed-off-by: Quinn Tran <quinn.tran@cavium.com>
Signed-off-by: Himanshu Madhani <himanshu.madhani@cavium.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/qla2xxx/qla_def.h

@@ -3266,6 +3266,7 @@ struct qla_qpair {
 	uint32_t fw_started:1;
 	uint32_t enable_class_2:1;
 	uint32_t enable_explicit_conf:1;
+	uint32_t use_shadow_reg:1;
 
 	uint16_t id;			/* qp number used with FW */
 	uint16_t vp_idx;		/* vport ID */

drivers/scsi/qla2xxx/qla_init.c

@@ -7614,6 +7614,7 @@ struct qla_qpair *qla2xxx_create_qpair(struct scsi_qla_host *vha, int qos,
 		qpair->vha = vha;
 		qpair->qp_lock_ptr = &qpair->qp_lock;
 		spin_lock_init(&qpair->qp_lock);
+		qpair->use_shadow_reg = IS_SHADOW_REG_CAPABLE(ha) ? 1 : 0;
 
 		/* Assign available que pair id */
 		mutex_lock(&ha->mq_lock);

drivers/scsi/qla2xxx/qla_os.c

@@ -384,6 +384,7 @@ static int qla2x00_alloc_queues(struct qla_hw_data *ha, struct req_que *req,
 	ha->base_qpair->rsp = rsp;
 	ha->base_qpair->vha = vha;
 	ha->base_qpair->qp_lock_ptr = &ha->hardware_lock;
+	ha->base_qpair->use_shadow_reg = IS_SHADOW_REG_CAPABLE(ha) ? 1 : 0;
 	/* init qpair to this cpu. Will adjust at run time. */
 	ha->base_qpair->msix = &ha->msix_entries[QLA_MSIX_RSP_Q];
 	INIT_LIST_HEAD(&ha->base_qpair->hints_list);

drivers/scsi/qla2xxx/qla_target.c

@@ -2288,7 +2288,8 @@ static int qlt_check_reserve_free_req(struct qla_qpair *qpair,
 	struct req_que *req = qpair->req;
 
 	if (req->cnt < (req_cnt + 2)) {
-		cnt = (uint16_t)RD_REG_DWORD(req->req_q_out);
+		cnt = (uint16_t)(qpair->use_shadow_reg ? *req->out_ptr :
+		    RD_REG_DWORD_RELAXED(req->req_q_out));
 
 		if  (req->ring_index < cnt)
 			req->cnt = cnt - req->ring_index;