This patch provides callbacks for struct net_device_ops for MTIP
L2 switch.

Signed-off-by: Lukasz Majewski <lukma@denx.de>

---
Changes for v13:
- New patch - created by excluding some code from large (i.e. v12 and
  earlier) MTIP driver
---
 .../net/ethernet/freescale/mtipsw/mtipl2sw.c  | 273 ++++++++++++++++++
 1 file changed, 273 insertions(+)

diff --git a/drivers/net/ethernet/freescale/mtipsw/mtipl2sw.c b/drivers/net/ethernet/freescale/mtipsw/mtipl2sw.c
index 5142f647d939..813cd39d6d56 100644
--- a/drivers/net/ethernet/freescale/mtipsw/mtipl2sw.c
+++ b/drivers/net/ethernet/freescale/mtipsw/mtipl2sw.c
@@ -43,6 +43,15 @@
 
 #include "mtipl2sw.h"
 
+static void swap_buffer(void *bufaddr, int len)
+{
+	int i;
+	unsigned int *buf = bufaddr;
+
+	for (i = 0; i < len; i += 4, buf++)
+		swab32s(buf);
+}
+
 /* Set the last buffer to wrap */
 static void mtip_set_last_buf_to_wrap(struct cbd_t *bdp)
 {
@@ -444,6 +453,128 @@ static void mtip_config_switch(struct switch_enet_private *fep)
 	       fep->hwp + ESW_IMR);
 }
 
+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(&fep->pdev->dev, "%s: tx queue full!.\n", dev->name);
+		spin_unlock_bh(&fep->hw_lock);
+		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],
+		       (void *)skb->data, skb->len);
+		bufaddr = fep->tx_bounce[index];
+	}
+
+	if (fep->quirks & FEC_QUIRK_SWAP_FRAME)
+		swap_buffer(bufaddr, skb->len);
+
+	/* Save skb pointer. */
+	fep->tx_skbuff[fep->skb_cur] = skb;
+
+	fep->skb_cur = (fep->skb_cur + 1) & TX_RING_MOD_MASK;
+
+	/* 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_errors++;
+		dev->stats.tx_dropped++;
+		dev_kfree_skb_any(skb);
+		goto err;
+	}
+
+	/* 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;
+
+	netif_trans_update(dev);
+	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;
+}
+
+static netdev_tx_t mtip_start_xmit(struct sk_buff *skb,
+				   struct net_device *dev)
+{
+	struct mtip_ndev_priv *priv = netdev_priv(dev);
+
+	return mtip_start_xmit_port(skb, dev, priv->portnum);
+}
+
 static void mtip_configure_enet_mii(struct switch_enet_private *fep, int port)
 {
 	struct phy_device *phydev = fep->phy_dev[port - 1];
@@ -601,6 +732,68 @@ static void mtip_switch_restart(struct net_device *dev, int duplex0,
 	mtip_config_switch(fep);
 }
 
+static void mtip_timeout(struct net_device *dev, unsigned int txqueue)
+{
+	struct mtip_ndev_priv *priv = netdev_priv(dev);
+	struct switch_enet_private *fep = priv->fep;
+	struct cbd_t *bdp;
+	int i;
+
+	dev->stats.tx_errors++;
+
+	if (IS_ENABLED(CONFIG_SWITCH_DEBUG)) {
+		dev_info(&dev->dev, "%s: transmit timed out.\n", dev->name);
+		dev_info(&dev->dev,
+			 "Ring data: cur_tx %lx%s, dirty_tx %lx cur_rx: %lx\n",
+			 (unsigned long)fep->cur_tx,
+			 fep->tx_full ? " (full)" : "",
+			 (unsigned long)fep->dirty_tx,
+			 (unsigned long)fep->cur_rx);
+
+		bdp = fep->tx_bd_base;
+		dev_info(&dev->dev, " tx: %u buffers\n", TX_RING_SIZE);
+		for (i = 0; i < TX_RING_SIZE; i++) {
+			dev_info(&dev->dev, "  %08lx: %04x %04x %08x\n",
+				 (kernel_ulong_t)bdp, bdp->cbd_sc,
+				 bdp->cbd_datlen, (int)bdp->cbd_bufaddr);
+			bdp++;
+		}
+
+		bdp = fep->rx_bd_base;
+		dev_info(&dev->dev, " rx: %lu buffers\n",
+			 (unsigned long)RX_RING_SIZE);
+		for (i = 0 ; i < RX_RING_SIZE; i++) {
+			dev_info(&dev->dev, "  %08lx: %04x %04x %08x\n",
+				 (kernel_ulong_t)bdp,
+				 bdp->cbd_sc, bdp->cbd_datlen,
+				 (int)bdp->cbd_bufaddr);
+			bdp++;
+		}
+	}
+
+	schedule_work(&priv->tx_timeout_work);
+}
+
+static void mtip_timeout_work(struct work_struct *work)
+{
+	struct mtip_ndev_priv *priv =
+		container_of(work, struct mtip_ndev_priv, tx_timeout_work);
+	struct switch_enet_private *fep = priv->fep;
+	struct net_device *dev = priv->dev;
+
+	rtnl_lock();
+	if (netif_device_present(dev) || netif_running(dev)) {
+		napi_disable(&fep->napi);
+		netif_tx_lock_bh(dev);
+		mtip_switch_restart(dev, fep->full_duplex[0],
+				    fep->full_duplex[1]);
+		netif_tx_wake_all_queues(dev);
+		netif_tx_unlock_bh(dev);
+		napi_enable(&fep->napi);
+	}
+	rtnl_unlock();
+}
+
 static irqreturn_t mtip_interrupt(int irq, void *ptr_fep)
 {
 	struct switch_enet_private *fep = ptr_fep;
@@ -1080,6 +1273,80 @@ static int mtip_close(struct net_device *dev)
 	return 0;
 }
 
+#define FEC_HASH_BITS	6		/* #bits in hash */
+static void mtip_set_multicast_list(struct net_device *dev)
+{
+	struct mtip_ndev_priv *priv = netdev_priv(dev);
+	unsigned int hash_high = 0, hash_low = 0, crc;
+	struct switch_enet_private *fep = priv->fep;
+	void __iomem *enet_addr = fep->enet_addr;
+	struct netdev_hw_addr *ha;
+	unsigned char hash;
+
+	if (priv->portnum == 2)
+		enet_addr += MCF_ESW_ENET_PORT_OFFSET;
+
+	if (dev->flags & IFF_PROMISC) {
+		/* Promisc mode is required for switch - it is
+		 * already enabled during driver's probe.
+		 */
+		dev_dbg(&dev->dev, "%s: IFF_PROMISC\n", __func__);
+		return;
+	}
+
+	if (dev->flags & IFF_ALLMULTI) {
+		dev_dbg(&dev->dev, "%s: IFF_ALLMULTI\n", __func__);
+
+		/* Allow all multicast addresses */
+		writel(0xFFFFFFFF, enet_addr + MCF_FEC_GRP_HASH_TABLE_HIGH);
+		writel(0xFFFFFFFF, enet_addr + MCF_FEC_GRP_HASH_TABLE_LOW);
+
+		return;
+	}
+
+	netdev_for_each_mc_addr(ha, dev) {
+		/* Calculate crc32 value of mac address */
+		crc = ether_crc_le(dev->addr_len, ha->addr);
+
+		/* Only upper 6 bits (FEC_HASH_BITS) are used
+		 * which point to specific bit in the hash registers
+		 */
+		hash = (crc >> (32 - FEC_HASH_BITS)) & 0x3F;
+
+		if (hash > 31)
+			hash_high |= 1 << (hash - 32);
+		else
+			hash_low |= 1 << hash;
+	}
+
+	writel(hash_high, enet_addr + MCF_FEC_GRP_HASH_TABLE_HIGH);
+	writel(hash_low, enet_addr + MCF_FEC_GRP_HASH_TABLE_LOW);
+}
+
+static int mtip_set_mac_address(struct net_device *dev, void *p)
+{
+	struct mtip_ndev_priv *priv = netdev_priv(dev);
+	struct switch_enet_private *fep = priv->fep;
+	void __iomem *enet_addr = fep->enet_addr;
+	struct sockaddr *addr = p;
+
+	if (!is_valid_ether_addr(addr->sa_data))
+		return -EADDRNOTAVAIL;
+	eth_hw_addr_set(dev, addr->sa_data);
+
+	if (priv->portnum == 2)
+		enet_addr += MCF_ESW_ENET_PORT_OFFSET;
+
+	writel(dev->dev_addr[3] | (dev->dev_addr[2] << 8) |
+	       (dev->dev_addr[1] << 16) | (dev->dev_addr[0] << 24),
+	       enet_addr + MCF_FEC_PALR);
+	writel((dev->dev_addr[5] << 16) | (dev->dev_addr[4] << 24),
+	       enet_addr + MCF_FEC_PAUR);
+
+	return mtip_update_atable_static((unsigned char *)dev->dev_addr,
+					 7, 7, fep);
+}
+
 static const struct ethtool_ops mtip_ethtool_ops = {
 	.get_link_ksettings     = phy_ethtool_get_link_ksettings,
 	.set_link_ksettings     = phy_ethtool_set_link_ksettings,
@@ -1091,6 +1358,10 @@ static const struct ethtool_ops mtip_ethtool_ops = {
 static const struct net_device_ops mtip_netdev_ops = {
 	.ndo_open		= mtip_open,
 	.ndo_stop		= mtip_close,
+	.ndo_start_xmit	= mtip_start_xmit,
+	.ndo_set_rx_mode	= mtip_set_multicast_list,
+	.ndo_tx_timeout	= mtip_timeout,
+	.ndo_set_mac_address	= mtip_set_mac_address,
 };
 
 bool mtip_is_switch_netdev_port(const struct net_device *ndev)
@@ -1192,6 +1463,8 @@ static int mtip_ndev_init(struct switch_enet_private *fep,
 			break;
 		}
 
+		INIT_WORK(&priv->tx_timeout_work, mtip_timeout_work);
+
 		dev_dbg(&fep->ndev[i]->dev, "%s: MTIP eth L2 switch %pM\n",
 			fep->ndev[i]->name, fep->ndev[i]->dev_addr);
 	}
-- 
2.39.5

On 6/22/25 11:37 AM, Lukasz Majewski wrote:
> This patch provides callbacks for struct net_device_ops for MTIP
> L2 switch.
> 
> Signed-off-by: Lukasz Majewski <lukma@denx.de>
> 
> ---
> Changes for v13:
> - New patch - created by excluding some code from large (i.e. v12 and
>   earlier) MTIP driver
> ---
>  .../net/ethernet/freescale/mtipsw/mtipl2sw.c  | 273 ++++++++++++++++++
>  1 file changed, 273 insertions(+)
> 
> diff --git a/drivers/net/ethernet/freescale/mtipsw/mtipl2sw.c b/drivers/net/ethernet/freescale/mtipsw/mtipl2sw.c
> index 5142f647d939..813cd39d6d56 100644
> --- a/drivers/net/ethernet/freescale/mtipsw/mtipl2sw.c
> +++ b/drivers/net/ethernet/freescale/mtipsw/mtipl2sw.c
> @@ -43,6 +43,15 @@
>  
>  #include "mtipl2sw.h"
>  
> +static void swap_buffer(void *bufaddr, int len)
> +{
> +	int i;
> +	unsigned int *buf = bufaddr;
> +
> +	for (i = 0; i < len; i += 4, buf++)
> +		swab32s(buf);
> +}
> +
>  /* Set the last buffer to wrap */
>  static void mtip_set_last_buf_to_wrap(struct cbd_t *bdp)
>  {
> @@ -444,6 +453,128 @@ static void mtip_config_switch(struct switch_enet_private *fep)
>  	       fep->hwp + ESW_IMR);
>  }
>  
> +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(&fep->pdev->dev, "%s: tx queue full!.\n", dev->name);
> +		spin_unlock_bh(&fep->hw_lock);
> +		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],
> +		       (void *)skb->data, skb->len);
> +		bufaddr = fep->tx_bounce[index];
> +	}
> +
> +	if (fep->quirks & FEC_QUIRK_SWAP_FRAME)
> +		swap_buffer(bufaddr, skb->len);
> +
> +	/* Save skb pointer. */
> +	fep->tx_skbuff[fep->skb_cur] = skb;
> +
> +	fep->skb_cur = (fep->skb_cur + 1) & TX_RING_MOD_MASK;
> +
> +	/* 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_errors++;
> +		dev->stats.tx_dropped++;
> +		dev_kfree_skb_any(skb);
> +		goto err;
> +	}
> +
> +	/* 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;
> +
> +	netif_trans_update(dev);
> +	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);

You may want to stop the queue earlier, i.e. when 75% or the like of the
tx ring is full. Also you can use netif_txq_maybe_stop() - with txq ==
netdev_get_tx_queue(dev, 0)

[...]
> +static void mtip_timeout(struct net_device *dev, unsigned int txqueue)
> +{
> +	struct mtip_ndev_priv *priv = netdev_priv(dev);
> +	struct switch_enet_private *fep = priv->fep;
> +	struct cbd_t *bdp;
> +	int i;
> +
> +	dev->stats.tx_errors++;
> +
> +	if (IS_ENABLED(CONFIG_SWITCH_DEBUG)) {
> +		dev_info(&dev->dev, "%s: transmit timed out.\n", dev->name);
> +		dev_info(&dev->dev,
> +			 "Ring data: cur_tx %lx%s, dirty_tx %lx cur_rx: %lx\n",
> +			 (unsigned long)fep->cur_tx,
> +			 fep->tx_full ? " (full)" : "",
> +			 (unsigned long)fep->dirty_tx,
> +			 (unsigned long)fep->cur_rx);
> +
> +		bdp = fep->tx_bd_base;
> +		dev_info(&dev->dev, " tx: %u buffers\n", TX_RING_SIZE);
> +		for (i = 0; i < TX_RING_SIZE; i++) {
> +			dev_info(&dev->dev, "  %08lx: %04x %04x %08x\n",
> +				 (kernel_ulong_t)bdp, bdp->cbd_sc,
> +				 bdp->cbd_datlen, (int)bdp->cbd_bufaddr);
> +			bdp++;
> +		}
> +
> +		bdp = fep->rx_bd_base;
> +		dev_info(&dev->dev, " rx: %lu buffers\n",
> +			 (unsigned long)RX_RING_SIZE);
> +		for (i = 0 ; i < RX_RING_SIZE; i++) {
> +			dev_info(&dev->dev, "  %08lx: %04x %04x %08x\n",
> +				 (kernel_ulong_t)bdp,
> +				 bdp->cbd_sc, bdp->cbd_datlen,
> +				 (int)bdp->cbd_bufaddr);
> +			bdp++;
> +		}

Here you are traversing both rings without any lock, which looks race prone.

/P

Hi Paolo,

> On 6/22/25 11:37 AM, Lukasz Majewski wrote:
> > This patch provides callbacks for struct net_device_ops for MTIP
> > L2 switch.
> > 
> > Signed-off-by: Lukasz Majewski <lukma@denx.de>
> > 
> > ---
> > Changes for v13:
> > - New patch - created by excluding some code from large (i.e. v12
> > and earlier) MTIP driver
> > ---
> >  .../net/ethernet/freescale/mtipsw/mtipl2sw.c  | 273
> > ++++++++++++++++++ 1 file changed, 273 insertions(+)
> > 
> > diff --git a/drivers/net/ethernet/freescale/mtipsw/mtipl2sw.c
> > b/drivers/net/ethernet/freescale/mtipsw/mtipl2sw.c index
> > 5142f647d939..813cd39d6d56 100644 ---
> > a/drivers/net/ethernet/freescale/mtipsw/mtipl2sw.c +++
> > b/drivers/net/ethernet/freescale/mtipsw/mtipl2sw.c @@ -43,6 +43,15
> > @@ 
> >  #include "mtipl2sw.h"
> >  
> > +static void swap_buffer(void *bufaddr, int len)
> > +{
> > +	int i;
> > +	unsigned int *buf = bufaddr;
> > +
> > +	for (i = 0; i < len; i += 4, buf++)
> > +		swab32s(buf);
> > +}
> > +
> >  /* Set the last buffer to wrap */
> >  static void mtip_set_last_buf_to_wrap(struct cbd_t *bdp)
> >  {
> > @@ -444,6 +453,128 @@ static void mtip_config_switch(struct
> > switch_enet_private *fep) fep->hwp + ESW_IMR);
> >  }
> >  
> > +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(&fep->pdev->dev, "%s: tx queue full!.\n",
> > dev->name);
> > +		spin_unlock_bh(&fep->hw_lock);
> > +		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],
> > +		       (void *)skb->data, skb->len);
> > +		bufaddr = fep->tx_bounce[index];
> > +	}
> > +
> > +	if (fep->quirks & FEC_QUIRK_SWAP_FRAME)
> > +		swap_buffer(bufaddr, skb->len);
> > +
> > +	/* Save skb pointer. */
> > +	fep->tx_skbuff[fep->skb_cur] = skb;
> > +
> > +	fep->skb_cur = (fep->skb_cur + 1) & TX_RING_MOD_MASK;
> > +
> > +	/* 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_errors++;
> > +		dev->stats.tx_dropped++;
> > +		dev_kfree_skb_any(skb);
> > +		goto err;
> > +	}
> > +
> > +	/* 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;
> > +
> > +	netif_trans_update(dev);
> > +	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);  
> 
> You may want to stop the queue earlier, i.e. when 75% or the like of
> the tx ring is full. Also you can use netif_txq_maybe_stop() - with
> txq == netdev_get_tx_queue(dev, 0)

There are two main reasons why the netif queue management is so rugged:

1. Due to simplicity - this driver is not using txq (queues), so I
cannot use APIs using as input argument queues. That is why functions
accepting only struct netdev pointer are used.

2. My feeling is that I would need to use queues abstraction only for
one queue - so this would be extra code overhead. I'm trying to
upstream driver which in fact has very simple internals (i.e. ringbuf
with 16 descriptors for tx/rx).

> 
> [...]
> > +static void mtip_timeout(struct net_device *dev, unsigned int
> > txqueue) +{
> > +	struct mtip_ndev_priv *priv = netdev_priv(dev);
> > +	struct switch_enet_private *fep = priv->fep;
> > +	struct cbd_t *bdp;
> > +	int i;
> > +
> > +	dev->stats.tx_errors++;
> > +
> > +	if (IS_ENABLED(CONFIG_SWITCH_DEBUG)) {
> > +		dev_info(&dev->dev, "%s: transmit timed out.\n",
> > dev->name);
> > +		dev_info(&dev->dev,
> > +			 "Ring data: cur_tx %lx%s, dirty_tx %lx
> > cur_rx: %lx\n",
> > +			 (unsigned long)fep->cur_tx,
> > +			 fep->tx_full ? " (full)" : "",
> > +			 (unsigned long)fep->dirty_tx,
> > +			 (unsigned long)fep->cur_rx);
> > +
> > +		bdp = fep->tx_bd_base;
> > +		dev_info(&dev->dev, " tx: %u buffers\n",
> > TX_RING_SIZE);
> > +		for (i = 0; i < TX_RING_SIZE; i++) {
> > +			dev_info(&dev->dev, "  %08lx: %04x %04x
> > %08x\n",
> > +				 (kernel_ulong_t)bdp, bdp->cbd_sc,
> > +				 bdp->cbd_datlen,
> > (int)bdp->cbd_bufaddr);
> > +			bdp++;
> > +		}
> > +
> > +		bdp = fep->rx_bd_base;
> > +		dev_info(&dev->dev, " rx: %lu buffers\n",
> > +			 (unsigned long)RX_RING_SIZE);
> > +		for (i = 0 ; i < RX_RING_SIZE; i++) {
> > +			dev_info(&dev->dev, "  %08lx: %04x %04x
> > %08x\n",
> > +				 (kernel_ulong_t)bdp,
> > +				 bdp->cbd_sc, bdp->cbd_datlen,
> > +				 (int)bdp->cbd_bufaddr);
> > +			bdp++;
> > +		}  
> 
> Here you are traversing both rings without any lock, which looks race
> prone.

I will add  spin_{un}lock_bh(&fep->hw_lock); (this is only code used
for debugging, not production)

> 
> /P
> 




Best regards,

Lukasz Majewski

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