staging: android: ion: do not clear dma_address of unmapped heap

Since commit 54ef5b9 (staging: android: ion: Initialize dma_address
of new sg list") (Linux v4.17), the helper function dup_sg_table() called
by ion_dma_buf_attach() does not preserve the dma_address from the
original SG list. It is a problem for the unmapped heap, because
dma_buf_attach() followed by dma_buf_map_attachment() now returns a SG
table with NULL dma_address, which breaks tee_shm_register_fd().

This commit avoids the dma_address reset for the unmapped heap.

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Tested-by: Jerome Forissier <jerome.forissier@linaro.org> (HiKey960, SDP)
Tested-by: Etienne Carriere <etienne.carriere@linaro.org> (Qemu_v7/v8, SDP)

drivers/staging/android/ion/ion.c

@@ -171,7 +171,8 @@ static void ion_buffer_kmap_put(struct ion_buffer *buffer)
 	}
 }
 
-static struct sg_table *dup_sg_table(struct sg_table *table)
+static struct sg_table *dup_sg_table(struct sg_table *table,
+				     bool preserve_dma_address)
 {
 	struct sg_table *new_table;
 	int ret, i;
@@ -190,7 +191,8 @@ static struct sg_table *dup_sg_table(struct sg_table *table)
 	new_sg = new_table->sgl;
 	for_each_sg(table->sgl, sg, table->nents, i) {
 		memcpy(new_sg, sg, sizeof(*sg));
-		new_sg->dma_address = 0;
+		if (!preserve_dma_address)
+			new_sg->dma_address = 0;
 		new_sg = sg_next(new_sg);
 	}
 
@@ -221,15 +223,15 @@ static int ion_dma_buf_attach(struct dma_buf *dmabuf,
 	if (!a)
 		return -ENOMEM;
 
-	table = dup_sg_table(buffer->sg_table);
+	if (buffer->heap->type == ION_HEAP_TYPE_UNMAPPED)
+		a->no_map = true;
+
+	table = dup_sg_table(buffer->sg_table, a->no_map);
 	if (IS_ERR(table)) {
 		kfree(a);
 		return -ENOMEM;
 	}
 
-	if (buffer->heap->type == ION_HEAP_TYPE_UNMAPPED)
-		a->no_map = true;
-
 	a->table = table;
 	a->dev = attachment->dev;
 	INIT_LIST_HEAD(&a->list);