Store a XSK buffer pool per queue, assigned through .ndo_bpf() with
command == XDP_SETUP_XSK_POOL.

We have no sequence upstream to disable a single queue, free its
buffers, refill it and re-enable the queue (without affecting other
queues). Therefore we protect our operation with interface-wide close
and open.

Also, prepare the terrain with a .ndo_xsk_wakeup() operation that does
the pre-flight-checks but is a no-op.

Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
---
 drivers/net/ethernet/cadence/macb.h      |  1 +
 drivers/net/ethernet/cadence/macb_main.c | 66 +++++++++++++++++++++++++++++++-
 2 files changed, 66 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/cadence/macb.h b/drivers/net/ethernet/cadence/macb.h
index 009a44e94726..a9e6f0289ecb 100644
--- a/drivers/net/ethernet/cadence/macb.h
+++ b/drivers/net/ethernet/cadence/macb.h
@@ -1278,6 +1278,7 @@ struct macb_queue {
 	struct napi_struct	napi_rx;
 	struct queue_stats stats;
 	struct page_pool	*page_pool;
+	struct xsk_buff_pool	*xsk_pool;
 	struct sk_buff		*skb;
 	struct xdp_rxq_info	xdp_rxq;
 };
diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index 65c2ec2a843c..a72d59ffd1cf 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -38,6 +38,7 @@
 #include <linux/types.h>
 #include <linux/udp.h>
 #include <net/pkt_sched.h>
+#include <net/xdp_sock_drv.h>
 #include "macb.h"
 
 /* This structure is only used for MACB on SiFive FU540 devices */
@@ -1564,6 +1565,24 @@ static int gem_xdp_xmit(struct net_device *dev, int num_frame,
 	return xmitted;
 }
 
+static int gem_xsk_wakeup(struct net_device *dev, u32 qid, u32 flags)
+{
+	struct macb *bp = netdev_priv(dev);
+	struct macb_queue *queue = &bp->queues[qid];
+
+	if (unlikely(!netif_carrier_ok(dev)))
+		return -ENETDOWN;
+
+	if (unlikely(qid >= bp->num_queues ||
+		     !rcu_access_pointer(bp->prog) ||
+		     !queue->xsk_pool))
+		return -ENXIO;
+
+	/* no-op, until rx/tx implement XSK support */
+
+	return 0;
+}
+
 static u32 gem_xdp_run(struct macb_queue *queue, void *buff_head,
 		       unsigned int *len, unsigned int *headroom,
 		       dma_addr_t addr)
@@ -3580,6 +3599,46 @@ static int gem_xdp_setup(struct net_device *dev, struct bpf_prog *prog,
 	return err;
 }
 
+static int gem_xdp_setup_xsk_pool(struct net_device *netdev,
+				  struct xsk_buff_pool *pool, u16 qid)
+{
+	struct macb *bp = netdev_priv(netdev);
+	unsigned long attrs = DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_WEAK_ORDERING;
+	struct macb_queue *queue = &bp->queues[qid];
+	bool running = netif_running(netdev);
+	struct device *dev = &bp->pdev->dev;
+	int err = 0;
+
+	if (qid >= bp->num_queues)
+		return -EINVAL;
+
+	if (pool && queue->xsk_pool)
+		return -EBUSY;
+
+	if (running)
+		macb_close(netdev);
+
+	if (pool) {
+		err = xsk_pool_dma_map(pool, dev, attrs);
+		if (err)
+			netdev_err(netdev, "xdp: failed to DMA map XSK pool\n");
+		else
+			queue->xsk_pool = pool;
+	} else {
+		if (queue->xsk_pool)
+			xsk_pool_dma_unmap(queue->xsk_pool, attrs);
+		queue->xsk_pool = NULL;
+	}
+
+	if (running) {
+		int err_open = macb_open(netdev);
+
+		err = err ?: err_open;
+	}
+
+	return err;
+}
+
 static int gem_xdp(struct net_device *dev, struct netdev_bpf *xdp)
 {
 	struct macb *bp = netdev_priv(dev);
@@ -3590,6 +3649,9 @@ static int gem_xdp(struct net_device *dev, struct netdev_bpf *xdp)
 	switch (xdp->command) {
 	case XDP_SETUP_PROG:
 		return gem_xdp_setup(dev, xdp->prog, xdp->extack);
+	case XDP_SETUP_XSK_POOL:
+		return gem_xdp_setup_xsk_pool(dev, xdp->xsk.pool,
+					      xdp->xsk.queue_id);
 	default:
 		return -EOPNOTSUPP;
 	}
@@ -4852,6 +4914,7 @@ static const struct net_device_ops macb_netdev_ops = {
 	.ndo_setup_tc		= macb_setup_tc,
 	.ndo_bpf		= gem_xdp,
 	.ndo_xdp_xmit		= gem_xdp_xmit,
+	.ndo_xsk_wakeup		= gem_xsk_wakeup,
 };
 
 /* Configure peripheral capabilities according to device tree
@@ -6156,7 +6219,8 @@ static int macb_probe(struct platform_device *pdev)
 
 		dev->xdp_features = NETDEV_XDP_ACT_BASIC |
 				    NETDEV_XDP_ACT_REDIRECT |
-				    NETDEV_XDP_ACT_NDO_XMIT;
+				    NETDEV_XDP_ACT_NDO_XMIT |
+				    NETDEV_XDP_ACT_XSK_ZEROCOPY;
 	}
 
 	netif_carrier_off(dev);

-- 
2.53.0