Re: [net-next v14 06/12] net: mtip: Add net_device_ops functions to the L2 switch driver

[Lukasz Majewski <lukma@denx.de>]

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Hi Paolo,

> On 7/1/25 1:49 PM, Lukasz Majewski wrote:
> > +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(&fep->hw_lock);  
> 
> mtip_start_xmit_port() runs with BH disabled. The above lock variant
> is inconsistent with what you use in patch 4.

I've looked into the fec_main.c driver. They use for TX path
__netif_tx_lock(nq, cpu); which is a simple spin_lock(). I've followed
the same approach (as _irqsave() seems to be an overkill).

This function (mtip_start_xmit_port()) is call as a callback from:
.ndo_start_xmit (member of struct net_device_ops).

IIRC net core code provides locking on this call anyway.

> Please be sure to run
> tests vs the next iteration with CONFIG_PROVE_LOCKING enabled.

This is already enabled. Locking in this driver is a bit special, as
one uDMA is used for both ports... (unlikely as in fec_main.c).

> 
> /P
> 




Best regards,

Lukasz Majewski

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