On Tue, 2022-05-31 at 15:21 +0530, Puranjay Mohan wrote:
[...]

+static int emac_tx_complete_packets(struct prueth_emac *emac, int chn,
+				    int budget)
+{
+	struct net_device *ndev = emac->ndev;
+	struct cppi5_host_desc_t *desc_tx;
+	struct netdev_queue *netif_txq;
+	struct prueth_tx_chn *tx_chn;
+	unsigned int total_bytes = 0;
+	struct sk_buff *skb;
+	dma_addr_t desc_dma;
+	int res, num_tx = 0;
+	void **swdata;
+
+	tx_chn = &emac->tx_chns[chn];
+
+	while (budget--) {
+		res = k3_udma_glue_pop_tx_chn(tx_chn->tx_chn, &desc_dma);
+		if (res == -ENODATA)
+			break;
+
+		/* teardown completion */
+		if (cppi5_desc_is_tdcm(desc_dma)) {
+			if (atomic_dec_and_test(&emac->tdown_cnt))
+				complete(&emac->tdown_complete);
+			break;
+		}
+
+		desc_tx = k3_cppi_desc_pool_dma2virt(tx_chn->desc_pool,
+						     desc_dma);
+		swdata = cppi5_hdesc_get_swdata(desc_tx);
+
+		skb = *(swdata);
+		prueth_xmit_free(tx_chn, desc_tx);
+
+		ndev = skb->dev;
+		ndev->stats.tx_packets++;
+		ndev->stats.tx_bytes += skb->len;
+		total_bytes += skb->len;
+		napi_consume_skb(skb, budget);

The above is uncorrect. In this loop's last iteration 'budget' will  be
0 and napi_consume_skb will wrongly assume the caller is not in NAPI
context. 

+static int prueth_dma_rx_push(struct prueth_emac *emac,
+			      struct sk_buff *skb,
+			      struct prueth_rx_chn *rx_chn)
+{
+	struct cppi5_host_desc_t *desc_rx;
+	struct net_device *ndev = emac->ndev;
+	dma_addr_t desc_dma;
+	dma_addr_t buf_dma;
+	u32 pkt_len = skb_tailroom(skb);
+	void **swdata;
+
+	desc_rx = k3_cppi_desc_pool_alloc(rx_chn->desc_pool);
+	if (!desc_rx) {
+		netdev_err(ndev, "rx push: failed to allocate descriptor\n");
+		return -ENOMEM;
+	}
+	desc_dma = k3_cppi_desc_pool_virt2dma(rx_chn->desc_pool, desc_rx);
+
+	buf_dma = dma_map_single(rx_chn->dma_dev, skb->data, pkt_len, DMA_FROM_DEVICE);
+	if (unlikely(dma_mapping_error(rx_chn->dma_dev, buf_dma))) {
+		k3_cppi_desc_pool_free(rx_chn->desc_pool, desc_rx);
+		netdev_err(ndev, "rx push: failed to map rx pkt buffer\n");
+		return -EINVAL;
+	}
+
+	cppi5_hdesc_init(desc_rx, CPPI5_INFO0_HDESC_EPIB_PRESENT,
+			 PRUETH_NAV_PS_DATA_SIZE);
+	k3_udma_glue_rx_dma_to_cppi5_addr(rx_chn->rx_chn, &buf_dma);
+	cppi5_hdesc_attach_buf(desc_rx, buf_dma, skb_tailroom(skb), buf_dma, skb_tailroom(skb));
+
+	swdata = cppi5_hdesc_get_swdata(desc_rx);
+	*swdata = skb;
+
+	return k3_udma_glue_push_rx_chn(rx_chn->rx_chn, 0,
+					desc_rx, desc_dma);
+}
+
+static int emac_rx_packet(struct prueth_emac *emac, u32 flow_id)
+{
+	struct prueth_rx_chn *rx_chn = &emac->rx_chns;
+	struct net_device *ndev = emac->ndev;
+	struct cppi5_host_desc_t *desc_rx;
+	dma_addr_t desc_dma, buf_dma;
+	u32 buf_dma_len, pkt_len, port_id = 0;
+	int ret;
+	void **swdata;
+	struct sk_buff *skb, *new_skb;
+
+	ret = k3_udma_glue_pop_rx_chn(rx_chn->rx_chn, flow_id, &desc_dma);
+	if (ret) {
+		if (ret != -ENODATA)
+			netdev_err(ndev, "rx pop: failed: %d\n", ret);
+		return ret;
+	}
+
+	if (cppi5_desc_is_tdcm(desc_dma)) /* Teardown ? */
+		return 0;
+
+	desc_rx = k3_cppi_desc_pool_dma2virt(rx_chn->desc_pool, desc_dma);
+
+	swdata = cppi5_hdesc_get_swdata(desc_rx);
+	skb = *swdata;
+
+	cppi5_hdesc_get_obuf(desc_rx, &buf_dma, &buf_dma_len);
+	k3_udma_glue_rx_cppi5_to_dma_addr(rx_chn->rx_chn, &buf_dma);
+	pkt_len = cppi5_hdesc_get_pktlen(desc_rx);
+	/* firmware adds 4 CRC bytes, strip them */
+	pkt_len -= 4;
+	cppi5_desc_get_tags_ids(&desc_rx->hdr, &port_id, NULL);
+
+	dma_unmap_single(rx_chn->dma_dev, buf_dma, buf_dma_len, DMA_FROM_DEVICE);
+	k3_cppi_desc_pool_free(rx_chn->desc_pool, desc_rx);
+
+	skb->dev = ndev;
+	if (!netif_running(skb->dev)) {
+		dev_kfree_skb_any(skb);
+		return 0;
+	}
+
+	new_skb = netdev_alloc_skb_ip_align(ndev, PRUETH_MAX_PKT_SIZE);
+	/* if allocation fails we drop the packet but push the
+	 * descriptor back to the ring with old skb to prevent a stall
+	 */
+	if (!new_skb) {
+		ndev->stats.rx_dropped++;
+		new_skb = skb;
+	} else {
+		/* send the filled skb up the n/w stack */
+		skb_put(skb, pkt_len);
+		skb->protocol = eth_type_trans(skb, ndev);
+		netif_receive_skb(skb);

This is (apparently) in napi context. You should use napi_gro_receive()
or napi_gro_frags()


Cheers!

Paolo