eth: fbnic: Add support for XDP_TX action

Add support for XDP_TX action and cleaning the associated work.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Mohsin Bashir <mohsin.bashr@gmail.com>
Link: https://patch.msgid.link/20250813221319.3367670-8-mohsin.bashr@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/ethernet/meta/fbnic/fbnic_txrx.c

@@ -19,6 +19,7 @@
 enum {
 	FBNIC_XDP_PASS = 0,
 	FBNIC_XDP_CONSUME,
+	FBNIC_XDP_TX,
 	FBNIC_XDP_LEN_ERR,
 };
 
@@ -1020,6 +1021,80 @@ static struct sk_buff *fbnic_build_skb(struct fbnic_napi_vector *nv,
 	return skb;
 }
 
+static long fbnic_pkt_tx(struct fbnic_napi_vector *nv,
+			 struct fbnic_pkt_buff *pkt)
+{
+	struct fbnic_ring *ring = &nv->qt[0].sub1;
+	int size, offset, nsegs = 1, data_len = 0;
+	unsigned int tail = ring->tail;
+	struct skb_shared_info *shinfo;
+	skb_frag_t *frag = NULL;
+	struct page *page;
+	dma_addr_t dma;
+	__le64 *twd;
+
+	if (unlikely(xdp_buff_has_frags(&pkt->buff))) {
+		shinfo = xdp_get_shared_info_from_buff(&pkt->buff);
+		nsegs += shinfo->nr_frags;
+		data_len = shinfo->xdp_frags_size;
+		frag = &shinfo->frags[0];
+	}
+
+	if (fbnic_desc_unused(ring) < nsegs)
+		return -FBNIC_XDP_CONSUME;
+
+	page = virt_to_page(pkt->buff.data_hard_start);
+	offset = offset_in_page(pkt->buff.data);
+	dma = page_pool_get_dma_addr(page);
+
+	size = pkt->buff.data_end - pkt->buff.data;
+
+	while (nsegs--) {
+		dma_sync_single_range_for_device(nv->dev, dma, offset, size,
+						 DMA_BIDIRECTIONAL);
+		dma += offset;
+
+		ring->tx_buf[tail] = page;
+
+		twd = &ring->desc[tail];
+		*twd = cpu_to_le64(FIELD_PREP(FBNIC_TWD_ADDR_MASK, dma) |
+				   FIELD_PREP(FBNIC_TWD_LEN_MASK, size) |
+				   FIELD_PREP(FBNIC_TWD_TYPE_MASK,
+					      FBNIC_TWD_TYPE_AL));
+
+		tail++;
+		tail &= ring->size_mask;
+
+		if (!data_len)
+			break;
+
+		offset = skb_frag_off(frag);
+		page = skb_frag_page(frag);
+		dma = page_pool_get_dma_addr(page);
+
+		size = skb_frag_size(frag);
+		data_len -= size;
+		frag++;
+	}
+
+	*twd |= FBNIC_TWD_TYPE(LAST_AL);
+
+	ring->tail = tail;
+
+	return -FBNIC_XDP_TX;
+}
+
+static void fbnic_pkt_commit_tail(struct fbnic_napi_vector *nv,
+				  unsigned int pkt_tail)
+{
+	struct fbnic_ring *ring = &nv->qt[0].sub1;
+
+	/* Force DMA writes to flush before writing to tail */
+	dma_wmb();
+
+	writel(pkt_tail, ring->doorbell);
+}
+
 static struct sk_buff *fbnic_run_xdp(struct fbnic_napi_vector *nv,
 				     struct fbnic_pkt_buff *pkt)
 {
@@ -1040,6 +1115,8 @@ static struct sk_buff *fbnic_run_xdp(struct fbnic_napi_vector *nv,
 	case XDP_PASS:
 xdp_pass:
 		return fbnic_build_skb(nv, pkt);
+	case XDP_TX:
+		return ERR_PTR(fbnic_pkt_tx(nv, pkt));
 	default:
 		bpf_warn_invalid_xdp_action(nv->napi.dev, xdp_prog, act);
 		fallthrough;
@@ -1104,10 +1181,10 @@ static int fbnic_clean_rcq(struct fbnic_napi_vector *nv,
 			   struct fbnic_q_triad *qt, int budget)
 {
 	unsigned int packets = 0, bytes = 0, dropped = 0, alloc_failed = 0;
+	s32 head0 = -1, head1 = -1, pkt_tail = -1;
 	u64 csum_complete = 0, csum_none = 0;
 	struct fbnic_ring *rcq = &qt->cmpl;
 	struct fbnic_pkt_buff *pkt;
-	s32 head0 = -1, head1 = -1;
 	__le64 *raw_rcd, done;
 	u32 head = rcq->head;
 
@@ -1163,6 +1240,9 @@ static int fbnic_clean_rcq(struct fbnic_napi_vector *nv,
 				bytes += skb->len;
 
 				napi_gro_receive(&nv->napi, skb);
+			} else if (skb == ERR_PTR(-FBNIC_XDP_TX)) {
+				pkt_tail = nv->qt[0].sub1.tail;
+				bytes += xdp_get_buff_len(&pkt->buff);
 			} else {
 				if (!skb) {
 					alloc_failed++;
@@ -1198,6 +1278,9 @@ static int fbnic_clean_rcq(struct fbnic_napi_vector *nv,
 	rcq->stats.rx.csum_none += csum_none;
 	u64_stats_update_end(&rcq->stats.syncp);
 
+	if (pkt_tail >= 0)
+		fbnic_pkt_commit_tail(nv, pkt_tail);
+
 	/* Unmap and free processed buffers */
 	if (head0 >= 0)
 		fbnic_clean_bdq(nv, budget, &qt->sub0, head0);