+static int ag71xx_fill_dma_desc(struct ag71xx_ring *ring, u32 addr, int len)
+{
+ int i;
+ struct ag71xx_desc *desc;
+ int ndesc = 0;
+ int split = ring->desc_split;
+
+ if (!split)
+ split = len;
+
+ while (len > 0) {
+ unsigned int cur_len = len;
+
+ i = (ring->curr + ndesc) % ring->size;
+ desc = ring->buf[i].desc;
+
+ if (!ag71xx_desc_empty(desc))
+ return -1;
+
+ if (cur_len > split) {
+ cur_len = split;
+
+ /*
+ * TX will hang if DMA transfers <= 4 bytes,
+ * make sure next segment is more than 4 bytes long.
+ */
+ if (len <= split + 4)
+ cur_len -= 4;
+ }
+
+ desc->data = addr;
+ addr += cur_len;
+ len -= cur_len;
+
+ if (len > 0)
+ cur_len |= DESC_MORE;
+
+ /* prevent early tx attempt of this descriptor */
+ if (!ndesc)
+ cur_len |= DESC_EMPTY;
+
+ desc->ctrl = cur_len;
+ ndesc++;
+ }
+
+ return ndesc;
+}
+