dpaa2-eth: Release buffers back to pool on XDP_DROP

Instead of freeing the RX buffers, release them back into the pool.
We wait for the maximum number of buffers supported by a single
release command to accumulate before issuing the command.

Also, don't unmap the Rx buffers at the beginning of the Rx routine
anymore, since that would require remapping them before release.
Instead, just do a DMA sync at first and only unmap if the frame is
meant for the stack.
Signed-off-by: NIoana Radulescu <ruxandra.radulescu@nxp.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c

@@ -217,10 +217,34 @@ static void free_bufs(struct dpaa2_eth_priv *priv, u64 *buf_array, int count)
 	}
 }
 
+static void xdp_release_buf(struct dpaa2_eth_priv *priv,
+			    struct dpaa2_eth_channel *ch,
+			    dma_addr_t addr)
+{
+	int err;
+
+	ch->xdp.drop_bufs[ch->xdp.drop_cnt++] = addr;
+	if (ch->xdp.drop_cnt < DPAA2_ETH_BUFS_PER_CMD)
+		return;
+
+	while ((err = dpaa2_io_service_release(ch->dpio, priv->bpid,
+					       ch->xdp.drop_bufs,
+					       ch->xdp.drop_cnt)) == -EBUSY)
+		cpu_relax();
+
+	if (err) {
+		free_bufs(priv, ch->xdp.drop_bufs, ch->xdp.drop_cnt);
+		ch->buf_count -= ch->xdp.drop_cnt;
+	}
+
+	ch->xdp.drop_cnt = 0;
+}
+
 static u32 run_xdp(struct dpaa2_eth_priv *priv,
 		   struct dpaa2_eth_channel *ch,
 		   struct dpaa2_fd *fd, void *vaddr)
 {
+	dma_addr_t addr = dpaa2_fd_get_addr(fd);
 	struct bpf_prog *xdp_prog;
 	struct xdp_buff xdp;
 	u32 xdp_act = XDP_PASS;
@@ -250,8 +274,7 @@ static u32 run_xdp(struct dpaa2_eth_priv *priv,
 	case XDP_ABORTED:
 		trace_xdp_exception(priv->net_dev, xdp_prog, xdp_act);
 	case XDP_DROP:
-		ch->buf_count--;
-		free_rx_fd(priv, fd, vaddr);
+		xdp_release_buf(priv, ch, addr);
 		break;
 	}
 
@@ -282,7 +305,8 @@ static void dpaa2_eth_rx(struct dpaa2_eth_priv *priv,
 	trace_dpaa2_rx_fd(priv->net_dev, fd);
 
 	vaddr = dpaa2_iova_to_virt(priv->iommu_domain, addr);
-	dma_unmap_single(dev, addr, DPAA2_ETH_RX_BUF_SIZE, DMA_FROM_DEVICE);
+	dma_sync_single_for_cpu(dev, addr, DPAA2_ETH_RX_BUF_SIZE,
+				DMA_FROM_DEVICE);
 
 	fas = dpaa2_get_fas(vaddr, false);
 	prefetch(fas);
@@ -300,10 +324,14 @@ static void dpaa2_eth_rx(struct dpaa2_eth_priv *priv,
 			return;
 		}
 
+		dma_unmap_single(dev, addr, DPAA2_ETH_RX_BUF_SIZE,
+				 DMA_FROM_DEVICE);
 		skb = build_linear_skb(ch, fd, vaddr);
 	} else if (fd_format == dpaa2_fd_sg) {
 		WARN_ON(priv->xdp_prog);
 
+		dma_unmap_single(dev, addr, DPAA2_ETH_RX_BUF_SIZE,
+				 DMA_FROM_DEVICE);
 		skb = build_frag_skb(priv, ch, buf_data);
 		skb_free_frag(vaddr);
 		percpu_extras->rx_sg_frames++;

drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.h

@@ -285,6 +285,8 @@ struct dpaa2_eth_fq {
 
 struct dpaa2_eth_ch_xdp {
 	struct bpf_prog *prog;
+	u64 drop_bufs[DPAA2_ETH_BUFS_PER_CMD];
+	int drop_cnt;
 };
 
 struct dpaa2_eth_channel {