net: axienet: Check for DMA mapping errors

Especially with the default 32-bit DMA mask, DMA buffers are a limited
resource, so their allocation can fail.
So as the DMA API documentation requires, add error checking code after
dma_map_single() calls to catch the case where we run out of "low" memory.
Signed-off-by: NAndre Przywara <andre.przywara@arm.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/xilinx/xilinx_axienet_main.c

@@ -248,6 +248,11 @@ static int axienet_dma_bd_init(struct net_device *ndev)
 						     skb->data,
 						     lp->max_frm_size,
 						     DMA_FROM_DEVICE);
+		if (dma_mapping_error(ndev->dev.parent, lp->rx_bd_v[i].phys)) {
+			netdev_err(ndev, "DMA mapping error\n");
+			goto out;
+		}
+
 		lp->rx_bd_v[i].cntrl = lp->max_frm_size;
 	}
 
@@ -679,6 +684,7 @@ axienet_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 	dma_addr_t tail_p;
 	struct axienet_local *lp = netdev_priv(ndev);
 	struct axidma_bd *cur_p;
+	u32 orig_tail_ptr = lp->tx_bd_tail;
 
 	num_frag = skb_shinfo(skb)->nr_frags;
 	cur_p = &lp->tx_bd_v[lp->tx_bd_tail];
@@ -714,9 +720,15 @@ axienet_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 		cur_p->app0 |= 2; /* Tx Full Checksum Offload Enabled */
 	}
 
-	cur_p->cntrl = skb_headlen(skb) | XAXIDMA_BD_CTRL_TXSOF_MASK;
 	cur_p->phys = dma_map_single(ndev->dev.parent, skb->data,
 				     skb_headlen(skb), DMA_TO_DEVICE);
+	if (unlikely(dma_mapping_error(ndev->dev.parent, cur_p->phys))) {
+		if (net_ratelimit())
+			netdev_err(ndev, "TX DMA mapping error\n");
+		ndev->stats.tx_dropped++;
+		return NETDEV_TX_OK;
+	}
+	cur_p->cntrl = skb_headlen(skb) | XAXIDMA_BD_CTRL_TXSOF_MASK;
 
 	for (ii = 0; ii < num_frag; ii++) {
 		if (++lp->tx_bd_tail >= lp->tx_bd_num)
@@ -727,6 +739,16 @@ axienet_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 					     skb_frag_address(frag),
 					     skb_frag_size(frag),
 					     DMA_TO_DEVICE);
+		if (unlikely(dma_mapping_error(ndev->dev.parent, cur_p->phys))) {
+			if (net_ratelimit())
+				netdev_err(ndev, "TX DMA mapping error\n");
+			ndev->stats.tx_dropped++;
+			axienet_free_tx_chain(ndev, orig_tail_ptr, ii + 1,
+					      NULL);
+			lp->tx_bd_tail = orig_tail_ptr;
+
+			return NETDEV_TX_OK;
+		}
 		cur_p->cntrl = skb_frag_size(frag);
 	}
 
@@ -807,6 +829,13 @@ static void axienet_recv(struct net_device *ndev)
 		cur_p->phys = dma_map_single(ndev->dev.parent, new_skb->data,
 					     lp->max_frm_size,
 					     DMA_FROM_DEVICE);
+		if (unlikely(dma_mapping_error(ndev->dev.parent, cur_p->phys))) {
+			if (net_ratelimit())
+				netdev_err(ndev, "RX DMA mapping error\n");
+			dev_kfree_skb(new_skb);
+			return;
+		}
+
 		cur_p->cntrl = lp->max_frm_size;
 		cur_p->status = 0;
 		cur_p->skb = new_skb;