diff --git a/drivers/scsi/aic94xx/aic94xx_task.c b/drivers/scsi/aic94xx/aic94xx_task.c
index 9b65abec2f6effbfd5fb26ab27c4214d6cec62f6..6c12c0f19f394ae0c87e0fac907dcb5785482aa4 100644
--- a/drivers/scsi/aic94xx/aic94xx_task.c
+++ b/drivers/scsi/aic94xx/aic94xx_task.c
@@ -74,8 +74,13 @@ static inline int asd_map_scatterlist(struct sas_task *task,
 		return 0;
 	}
 
-	num_sg = pci_map_sg(asd_ha->pcidev, task->scatter, task->num_scatter,
-			    task->data_dir);
+	/* STP tasks come from libata which has already mapped
+	 * the SG list */
+	if (task->task_proto == SAS_PROTOCOL_STP)
+		num_sg = task->num_scatter;
+	else
+		num_sg = pci_map_sg(asd_ha->pcidev, task->scatter,
+				    task->num_scatter, task->data_dir);
 	if (num_sg == 0)
 		return -ENOMEM;
 
@@ -120,8 +125,9 @@ static inline int asd_map_scatterlist(struct sas_task *task,
 
 	return 0;
 err_unmap:
-	pci_unmap_sg(asd_ha->pcidev, task->scatter, task->num_scatter,
-		     task->data_dir);
+	if (task->task_proto != SAS_PROTOCOL_STP)
+		pci_unmap_sg(asd_ha->pcidev, task->scatter, task->num_scatter,
+			     task->data_dir);
 	return res;
 }
 
@@ -142,8 +148,9 @@ static inline void asd_unmap_scatterlist(struct asd_ascb *ascb)
 	}
 
 	asd_free_coherent(asd_ha, ascb->sg_arr);
-	pci_unmap_sg(asd_ha->pcidev, task->scatter, task->num_scatter,
-		     task->data_dir);
+	if (task->task_proto != SAS_PROTOCOL_STP)
+		pci_unmap_sg(asd_ha->pcidev, task->scatter, task->num_scatter,
+			     task->data_dir);
 }
 
 /* ---------- Task complete tasklet ---------- */