[net-next v19 0/7] net: mtip: Add support for MTIP imx287 L2 switch driver

[net-next v19 0/7] net: mtip: Add support for MTIP imx287 L2 switch driver

[Lukasz Majewski]

This patch series adds support for More Than IP's L2 switch driver embedded
in some NXP's SoCs. This one has been tested on imx287, but is also available
in the vf610.

In the past there has been performed some attempts to upstream this driver:

1. The 4.19-cip based one [1]
2. DSA based one for 5.12 [2] - i.e. the switch itself was treat as a DSA switch
   with NO tag appended.
3. The extension for FEC driver for 5.12 [3] - the trick here was to fully reuse
   FEC when the in-HW switching is disabled. When bridge offloading is enabled,
   the driver uses already configured MAC and PHY to also configure PHY.

All three approaches were not accepted as eligible for upstreaming.

The driver from this series has floowing features:

1. It is fully separated from fec_main - i.e. can be used interchangeable
   with it. To be more specific - one can build them as modules and
   if required switch between them when e.g. bridge offloading is required.

   To be more specific:
        - Use FEC_MAIN: When one needs support for two ETH ports with separate
          uDMAs used for both and bridging can be realized in SW.

        - Use MTIPL2SW: When it is enough to support two ports with only uDMA0
          attached to switch and bridging shall be offloaded to HW. 

2. This driver uses MTIP's L2 switch internal VLAN feature to provide port
   separation at boot time. Port separation is disabled when bridging is
   required.

3. Example usage:
        Configuration:
        ip link set lan0 up; sleep 1;
        ip link set lan1 up; sleep 1;
        ip link add name br0 type bridge;
        ip link set br0 up; sleep 1;
        ip link set lan0 master br0;
        ip link set lan1 master br0;
        bridge link;
        ip addr add 192.168.2.17/24 dev br0;
        ping -c 5 192.168.2.222

        Removal:
        ip link set br0 down;
        ip link delete br0 type bridge;
        ip link set dev lan1 down
        ip link set dev lan0 down

4. Limitations:
        - Driver enables and disables switch operation with learning and ageing.
        - Missing is the advanced configuration (e.g. adding entries to FBD). This is
          on purpose, as up till now we didn't had consensus about how the driver
          shall be added to Linux.

5. Clang build:
	make LLVM_SUFFIX=-19 LLVM=1 mrproper
	cp ./arch/arm/configs/mxs_defconfig .config
	make ARCH=arm LLVM_SUFFIX=-19 LLVM=1 W=1 menuconfig
	make ARCH=arm LLVM_SUFFIX=-19 LLVM=1 W=1 -j8 LOADADDR=0x40008000 uImage dtbs

        make LLVM_SUFFIX=-19 LLVM=1 mrproper
        make LLVM_SUFFIX=-19 LLVM=1 allmodconfig
        make LLVM_SUFFIX=-19 LLVM=1 W=1 drivers/net/ethernet/freescale/mtipsw/ | tee llvm_build.log
        make LLVM_SUFFIX=-19 LLVM=1 W=1 -j8 | tee llvm_build.log

6. Kernel compliance checks:
	make coccicheck MODE=report J=4 M=drivers/net/ethernet/freescale/mtipsw/
	~/work/src/smatch/smatch_scripts/kchecker drivers/net/ethernet/freescale/mtipsw/

7. GCC
        make mrproper
        make allmodconfig
        make W=1 drivers/net/ethernet/freescale/mtipsw/

Links:
[1] - https://github.com/lmajewski/linux-imx28-l2switch/commits/master
[2] - https://github.com/lmajewski/linux-imx28-l2switch/tree/imx28-v5.12-L2-upstream-RFC_v1
[3] - https://source.denx.de/linux/linux-imx28-l2switch/-/tree/imx28-v5.12-L2-upstream-switchdev-RFC_v1?ref_type=heads

Lukasz Majewski (7):
  dt-bindings: net: Add MTIP L2 switch description
  net: mtip: The L2 switch driver for imx287
  net: mtip: Add buffers management functions to the L2 switch driver
  net: mtip: Add net_device_ops functions to the L2 switch driver
  net: mtip: Add mtip_switch_{rx|tx} functions to the L2 switch driver
  net: mtip: Extend the L2 switch driver with management operations
  net: mtip: Extend the L2 switch driver for imx287 with bridge
    operations

 .../bindings/net/nxp,imx28-mtip-switch.yaml   |  150 ++
 MAINTAINERS                                   |    7 +
 drivers/net/ethernet/freescale/Kconfig        |    1 +
 drivers/net/ethernet/freescale/Makefile       |    1 +
 drivers/net/ethernet/freescale/mtipsw/Kconfig |   13 +
 .../net/ethernet/freescale/mtipsw/Makefile    |    4 +
 .../net/ethernet/freescale/mtipsw/mtipl2sw.c  | 1984 +++++++++++++++++
 .../net/ethernet/freescale/mtipsw/mtipl2sw.h  |  651 ++++++
 .../ethernet/freescale/mtipsw/mtipl2sw_br.c   |  132 ++
 .../ethernet/freescale/mtipsw/mtipl2sw_mgnt.c |  443 ++++
 10 files changed, 3386 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/net/nxp,imx28-mtip-switch.yaml
 create mode 100644 drivers/net/ethernet/freescale/mtipsw/Kconfig
 create mode 100644 drivers/net/ethernet/freescale/mtipsw/Makefile
 create mode 100644 drivers/net/ethernet/freescale/mtipsw/mtipl2sw.c
 create mode 100644 drivers/net/ethernet/freescale/mtipsw/mtipl2sw.h
 create mode 100644 drivers/net/ethernet/freescale/mtipsw/mtipl2sw_br.c
 create mode 100644 drivers/net/ethernet/freescale/mtipsw/mtipl2sw_mgnt.c

-- 
2.39.5

Re: [net-next v19 4/7] net: mtip: Add net_device_ops functions to the L2 switch driver

[Jakub Kicinski]

On Mon, 25 Aug 2025 00:07:33 +0200 Lukasz Majewski wrote:
> +	/* Set buffer length and buffer pointer */
> +	bufaddr = skb->data;

You can't write (swap) skb->data if the skb is a clone..

> +	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) {

add 
	.. ||
	(fep->quirks & FEC_QUIRK_SWAP_FRAME && skb_cloned(skb))

here to switch to the local buffer for clones ?

> +		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);

> +	if (unlikely(dma_mapping_error(&fep->pdev->dev, bdp->cbd_bufaddr))) {
> +		dev_err(&fep->pdev->dev,
> +			"Failed to map descriptor tx buffer\n");

All per-packet prints must be rate limited

> +		/* Since we have freed up a buffer, the ring is no longer
> +		 * full.
> +		 */
> +		if (fep->tx_full) {
> +			fep->tx_full = 0;
> +			if (netif_queue_stopped(dev))
> +				netif_wake_queue(dev);
> +		}

I must say I'm still quite confused by the netdev management in this
driver. You seem to have 2 netdevs, one per port. There's one
set of queues and one NAPI. Whichever netdev gets up first gets the
NAPI. What makes my head spin is that you seem to record which
netdev/port was doing Rx _last_ and then pass that netdev to
mtip_switch_tx(). Why? Isn't the dev that we're completing Tx for is
best read from skb->dev packet by packet? Also this wake up logic looks
like it will wake up _one_ netdev's queue and then set tx_full = 0, so
presumably it will not wake the other port if both ports queues were
stopped. Why keep tx_full state in the first place? Just check if the
queues is stopped..?

Re: [net-next v19 5/7] net: mtip: Add mtip_switch_{rx|tx} functions to the L2 switch driver

[Jakub Kicinski]

On Mon, 25 Aug 2025 00:07:34 +0200 Lukasz Majewski wrote:
>  static void mtip_switch_tx(struct net_device *dev)
>  {
> +	struct mtip_ndev_priv *priv = netdev_priv(dev);
> +	struct switch_enet_private *fep = priv->fep;
> +	unsigned short status;
> +	struct sk_buff *skb;
> +	struct cbd_t *bdp;

> +		} else {
> +			dev->stats.tx_packets++;
> +		}
> +
> +		if (status & BD_ENET_TX_READY)
> +			dev_err(&fep->pdev->dev,
> +				"Enet xmit interrupt and TX_READY.\n");

per-pkt print, needs rl

> +		/* Free the sk buffer associated with this last transmit */
> +		dev_consume_skb_irq(skb);

why _irq()? this now runs from NAPI, so it's in BH. Just stick 
to dev_comsume_skb_any(), it's the safest choice..

Re: [net-next v19 4/7] net: mtip: Add net_device_ops functions to the L2 switch driver

[Jakub Kicinski]

On Mon, 25 Aug 2025 00:07:33 +0200 Lukasz Majewski wrote:
> +
> +	/* On some FEC implementations data must be aligned on
> +	 * 4-byte boundaries. Use bounce buffers to copy data
> +	 * and get it aligned.spin
> +	 */

Almost forgot, the word "spin" appears here rather out of place.