Re: [net-next v16 06/12] net: mtip: Add net_device_ops functions to the L2 switch driver

Simon Horman
2025-07-25T16:17:51Z

On Fri, Jul 25, 2025 at 12:33:12AM +0200, Lukasz Majewski wrote:
> This patch provides callbacks for struct net_device_ops for MTIP
> L2 switch.
>
> Signed-off-by: Lukasz Majewski <lukma@denx.de>

...

> +static netdev_tx_t mtip_start_xmit_port(struct sk_buff *skb,
> + struct net_device *dev, int port)
> +{
> + struct mtip_ndev_priv *priv = netdev_priv(dev);
> + struct switch_enet_private *fep = priv->fep;
> + unsigned short status;
> + struct cbd_t *bdp;
> + void *bufaddr;
> +
> + spin_lock_bh(&fep->hw_lock);
> +
> + if (!fep->link[0] && !fep->link[1]) {
> + /* Link is down or autonegotiation is in progress. */
> + netif_stop_queue(dev);
> + spin_unlock_bh(&fep->hw_lock);
> + return NETDEV_TX_BUSY;
> + }
> +
> + /* Fill in a Tx ring entry */
> + bdp = fep->cur_tx;
> + status = bdp->cbd_sc;
> +
> + if (status & BD_ENET_TX_READY) {
> + /* All transmit buffers are full. Bail out.
> + * This should not happen, since dev->tbusy should be set.
> + */
> + netif_stop_queue(dev);
> + dev_err_ratelimited(&fep->pdev->dev, "%s: tx queue full!.\n",
> + dev->name);
> + spin_unlock(&fep->hw_lock);

Sorry be the one to point out this needle in a haystack,
but this should be spin_unlock_bh()

Flagged by Smatch.

> + return NETDEV_TX_BUSY;
> + }
> +
> + /* Clear all of the status flags */
> + status &= ~BD_ENET_TX_STATS;
> +
> + /* Set buffer length and buffer pointer */
> + bufaddr = skb->data;
> + bdp->cbd_datlen = skb->len;
> +
> + /* On some FEC implementations data must be aligned on
> + * 4-byte boundaries. Use bounce buffers to copy data
> + * and get it aligned.spin
> + */
> + if ((unsigned long)bufaddr & MTIP_ALIGNMENT) {
> + unsigned int index;
> +
> + index = bdp - fep->tx_bd_base;
> + memcpy(fep->tx_bounce[index], skb->data, skb->len);
> + bufaddr = fep->tx_bounce[index];
> + }
> +
> + if (fep->quirks & FEC_QUIRK_SWAP_FRAME)
> + swap_buffer(bufaddr, skb->len);
> +
> + /* Push the data cache so the CPM does not get stale memory
> + * data.
> + */
> + bdp->cbd_bufaddr = dma_map_single(&fep->pdev->dev, bufaddr,
> + MTIP_SWITCH_TX_FRSIZE,
> + DMA_TO_DEVICE);
> + if (unlikely(dma_mapping_error(&fep->pdev->dev, bdp->cbd_bufaddr))) {
> + dev_err(&fep->pdev->dev,
> + "Failed to map descriptor tx buffer\n");
> + dev->stats.tx_dropped++;
> + dev_kfree_skb_any(skb);
> + goto err;
> + }
> +
> + /* Save skb pointer. */
> + fep->tx_skbuff[fep->skb_cur] = skb;
> + fep->skb_cur = (fep->skb_cur + 1) & TX_RING_MOD_MASK;
> +
> + /* Send it on its way. Tell FEC it's ready, interrupt when done,
> + * it's the last BD of the frame, and to put the CRC on the end.
> + */
> +
> + status |= (BD_ENET_TX_READY | BD_ENET_TX_INTR | BD_ENET_TX_LAST |
> + BD_ENET_TX_TC);
> +
> + /* Synchronize all descriptor writes */
> + wmb();
> + bdp->cbd_sc = status;
> +
> + skb_tx_timestamp(skb);
> +
> + /* Trigger transmission start */
> + writel(MCF_ESW_TDAR_X_DES_ACTIVE, fep->hwp + ESW_TDAR);
> +
> + dev->stats.tx_bytes += skb->len;
> + /* If this was the last BD in the ring,
> + * start at the beginning again.
> + */
> + if (status & BD_ENET_TX_WRAP)
> + bdp = fep->tx_bd_base;
> + else
> + bdp++;
> +
> + if (bdp == fep->dirty_tx) {
> + fep->tx_full = 1;
> + netif_stop_queue(dev);
> + }
> +
> + fep->cur_tx = bdp;
> + err:
> + spin_unlock_bh(&fep->hw_lock);
> +
> + return NETDEV_TX_OK;
> +}

...