[PATCH net-next v4 4/7] dpaa_eth: add XDP_TX support

[Camelia Groza <camelia.groza@nxp.com>]

Use an xdp_frame structure for managing the frame. Store a backpointer to
the structure at the start of the buffer before enqueueing for cleanup
on TX confirmation. Reserve DPAA_TX_PRIV_DATA_SIZE bytes from the frame
size shared with the XDP program for this purpose. Use the XDP
API for freeing the buffer when it returns to the driver on the TX
confirmation path.

The frame queues are shared with the netstack.

This approach will be reused for XDP REDIRECT.

Acked-by: Madalin Bucur <madalin.bucur@oss.nxp.com>
Signed-off-by: Camelia Groza <camelia.groza@nxp.com>
---
Changes in v4:
- call xdp_rxq_info_is_reg() before unregistering
- minor cleanups (remove unneeded variable, print error code)
- add more details in the commit message
- did not call qman_destroy_fq() in case of xdp_rxq_info_reg() failure
since it would lead to a double free of the fq resources

 drivers/net/ethernet/freescale/dpaa/dpaa_eth.c | 128 ++++++++++++++++++++++++-
 drivers/net/ethernet/freescale/dpaa/dpaa_eth.h |   2 +
 2 files changed, 125 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
index ee076f4..0deffcc 100644
--- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
+++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
@@ -1130,6 +1130,24 @@ static int dpaa_fq_init(struct dpaa_fq *dpaa_fq, bool td_enable)

 	dpaa_fq->fqid = qman_fq_fqid(fq);

+	if (dpaa_fq->fq_type == FQ_TYPE_RX_DEFAULT ||
+	    dpaa_fq->fq_type == FQ_TYPE_RX_PCD) {
+		err = xdp_rxq_info_reg(&dpaa_fq->xdp_rxq, dpaa_fq->net_dev,
+				       dpaa_fq->fqid);
+		if (err) {
+			dev_err(dev, "xdp_rxq_info_reg() = %d\n", err);
+			return err;
+		}
+
+		err = xdp_rxq_info_reg_mem_model(&dpaa_fq->xdp_rxq,
+						 MEM_TYPE_PAGE_ORDER0, NULL);
+		if (err) {
+			dev_err(dev, "xdp_rxq_info_reg_mem_model() = %d\n", err);
+			xdp_rxq_info_unreg(&dpaa_fq->xdp_rxq);
+			return err;
+		}
+	}
+
 	return 0;
 }

@@ -1159,6 +1177,11 @@ static int dpaa_fq_free_entry(struct device *dev, struct qman_fq *fq)
 		}
 	}

+	if ((dpaa_fq->fq_type == FQ_TYPE_RX_DEFAULT ||
+	     dpaa_fq->fq_type == FQ_TYPE_RX_PCD) &&
+	    xdp_rxq_info_is_reg(&dpaa_fq->xdp_rxq))
+		xdp_rxq_info_unreg(&dpaa_fq->xdp_rxq);
+
 	qman_destroy_fq(fq);
 	list_del(&dpaa_fq->list);

@@ -1625,6 +1648,9 @@ static int dpaa_eth_refill_bpools(struct dpaa_priv *priv)
  *
  * Return the skb backpointer, since for S/G frames the buffer containing it
  * gets freed here.
+ *
+ * No skb backpointer is set when transmitting XDP frames. Cleanup the buffer
+ * and return NULL in this case.
  */
 static struct sk_buff *dpaa_cleanup_tx_fd(const struct dpaa_priv *priv,
 					  const struct qm_fd *fd, bool ts)
@@ -1664,13 +1690,21 @@ static struct sk_buff *dpaa_cleanup_tx_fd(const struct dpaa_priv *priv,
 		}
 	} else {
 		dma_unmap_single(priv->tx_dma_dev, addr,
-				 priv->tx_headroom + qm_fd_get_length(fd),
+				 qm_fd_get_offset(fd) + qm_fd_get_length(fd),
 				 dma_dir);
 	}

 	swbp = (struct dpaa_eth_swbp *)vaddr;
 	skb = swbp->skb;

+	/* No skb backpointer is set when running XDP. An xdp_frame
+	 * backpointer is saved instead.
+	 */
+	if (!skb) {
+		xdp_return_frame(swbp->xdpf);
+		return NULL;
+	}
+
 	/* DMA unmapping is required before accessing the HW provided info */
 	if (ts && priv->tx_tstamp &&
 	    skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP) {
@@ -2350,11 +2384,76 @@ static enum qman_cb_dqrr_result rx_error_dqrr(struct qman_portal *portal,
 	return qman_cb_dqrr_consume;
 }

+static int dpaa_xdp_xmit_frame(struct net_device *net_dev,
+			       struct xdp_frame *xdpf)
+{
+	struct dpaa_priv *priv = netdev_priv(net_dev);
+	struct rtnl_link_stats64 *percpu_stats;
+	struct dpaa_percpu_priv *percpu_priv;
+	struct dpaa_eth_swbp *swbp;
+	struct netdev_queue *txq;
+	void *buff_start;
+	struct qm_fd fd;
+	dma_addr_t addr;
+	int err;
+
+	percpu_priv = this_cpu_ptr(priv->percpu_priv);
+	percpu_stats = &percpu_priv->stats;
+
+	if (xdpf->headroom < DPAA_TX_PRIV_DATA_SIZE) {
+		err = -EINVAL;
+		goto out_error;
+	}
+
+	buff_start = xdpf->data - xdpf->headroom;
+
+	/* Leave empty the skb backpointer at the start of the buffer.
+	 * Save the XDP frame for easy cleanup on confirmation.
+	 */
+	swbp = (struct dpaa_eth_swbp *)buff_start;
+	swbp->skb = NULL;
+	swbp->xdpf = xdpf;
+
+	qm_fd_clear_fd(&fd);
+	fd.bpid = FSL_DPAA_BPID_INV;
+	fd.cmd |= cpu_to_be32(FM_FD_CMD_FCO);
+	qm_fd_set_contig(&fd, xdpf->headroom, xdpf->len);
+
+	addr = dma_map_single(priv->tx_dma_dev, buff_start,
+			      xdpf->headroom + xdpf->len,
+			      DMA_TO_DEVICE);
+	if (unlikely(dma_mapping_error(priv->tx_dma_dev, addr))) {
+		err = -EINVAL;
+		goto out_error;
+	}
+
+	qm_fd_addr_set64(&fd, addr);
+
+	/* Bump the trans_start */
+	txq = netdev_get_tx_queue(net_dev, smp_processor_id());
+	txq->trans_start = jiffies;
+
+	err = dpaa_xmit(priv, percpu_stats, smp_processor_id(), &fd);
+	if (err) {
+		dma_unmap_single(priv->tx_dma_dev, addr,
+				 qm_fd_get_offset(&fd) + qm_fd_get_length(&fd),
+				 DMA_TO_DEVICE);
+		goto out_error;
+	}
+
+	return 0;
+
+out_error:
+	percpu_stats->tx_errors++;
+	return err;
+}
+
 static u32 dpaa_run_xdp(struct dpaa_priv *priv, struct qm_fd *fd, void *vaddr,
-			unsigned int *xdp_meta_len)
+			struct dpaa_fq *dpaa_fq, unsigned int *xdp_meta_len)
 {
 	ssize_t fd_off = qm_fd_get_offset(fd);
 	struct bpf_prog *xdp_prog;
+	struct xdp_frame *xdpf;
 	struct xdp_buff xdp;
 	u32 xdp_act;

@@ -2370,7 +2469,8 @@ static u32 dpaa_run_xdp(struct dpaa_priv *priv, struct qm_fd *fd, void *vaddr,
 	xdp.data_meta = xdp.data;
 	xdp.data_hard_start = xdp.data - XDP_PACKET_HEADROOM;
 	xdp.data_end = xdp.data + qm_fd_get_length(fd);
-	xdp.frame_sz = DPAA_BP_RAW_SIZE;
+	xdp.frame_sz = DPAA_BP_RAW_SIZE - DPAA_TX_PRIV_DATA_SIZE;
+	xdp.rxq = &dpaa_fq->xdp_rxq;

 	xdp_act = bpf_prog_run_xdp(xdp_prog, &xdp);

@@ -2381,6 +2481,22 @@ static u32 dpaa_run_xdp(struct dpaa_priv *priv, struct qm_fd *fd, void *vaddr,
 	case XDP_PASS:
 		*xdp_meta_len = xdp.data - xdp.data_meta;
 		break;
+	case XDP_TX:
+		/* We can access the full headroom when sending the frame
+		 * back out
+		 */
+		xdp.data_hard_start = vaddr;
+		xdp.frame_sz = DPAA_BP_RAW_SIZE;
+		xdpf = xdp_convert_buff_to_frame(&xdp);
+		if (unlikely(!xdpf)) {
+			free_pages((unsigned long)vaddr, 0);
+			break;
+		}
+
+		if (dpaa_xdp_xmit_frame(priv->net_dev, xdpf))
+			xdp_return_frame_rx_napi(xdpf);
+
+		break;
 	default:
 		bpf_warn_invalid_xdp_action(xdp_act);
 		fallthrough;
@@ -2415,6 +2531,7 @@ static enum qman_cb_dqrr_result rx_default_dqrr(struct qman_portal *portal,
 	u32 fd_status, hash_offset;
 	struct qm_sg_entry *sgt;
 	struct dpaa_bp *dpaa_bp;
+	struct dpaa_fq *dpaa_fq;
 	struct dpaa_priv *priv;
 	struct sk_buff *skb;
 	int *count_ptr;
@@ -2423,9 +2540,10 @@ static enum qman_cb_dqrr_result rx_default_dqrr(struct qman_portal *portal,
 	u32 hash;
 	u64 ns;

+	dpaa_fq = container_of(fq, struct dpaa_fq, fq_base);
 	fd_status = be32_to_cpu(fd->status);
 	fd_format = qm_fd_get_format(fd);
-	net_dev = ((struct dpaa_fq *)fq)->net_dev;
+	net_dev = dpaa_fq->net_dev;
 	priv = netdev_priv(net_dev);
 	dpaa_bp = dpaa_bpid2pool(dq->fd.bpid);
 	if (!dpaa_bp)
@@ -2494,7 +2612,7 @@ static enum qman_cb_dqrr_result rx_default_dqrr(struct qman_portal *portal,

 	if (likely(fd_format == qm_fd_contig)) {
 		xdp_act = dpaa_run_xdp(priv, (struct qm_fd *)fd, vaddr,
-				       &xdp_meta_len);
+				       dpaa_fq, &xdp_meta_len);
 		if (xdp_act != XDP_PASS) {
 			percpu_stats->rx_packets++;
 			percpu_stats->rx_bytes += qm_fd_get_length(fd);
diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.h b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.h
index 94e8613..5c8d52a 100644
--- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.h
+++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.h
@@ -68,6 +68,7 @@ struct dpaa_fq {
 	u16 channel;
 	u8 wq;
 	enum dpaa_fq_type fq_type;
+	struct xdp_rxq_info xdp_rxq;
 };

 struct dpaa_fq_cbs {
@@ -150,6 +151,7 @@ struct dpaa_buffer_layout {
  */
 struct dpaa_eth_swbp {
 	struct sk_buff *skb;
+	struct xdp_frame *xdpf;
 };

 struct dpaa_priv {
--
1.9.1