Re: [PATCH RFC net-next 1/5] net: stmmac: call phylink_start() and phylink_stop() in XDP functions

[Furong Xu <0x1207@gmail.com>]

On Thu, 27 Feb 2025 15:05:02 +0000
"Russell King (Oracle)" <rmk+kernel@armlinux.org.uk> wrote:

> Phylink does not permit drivers to mess with the netif carrier, as
> this will de-synchronise phylink with the MAC driver. Moreover,
> setting and clearing the TE and RE bits via stmmac_mac_set() in this
> path is also wrong as the link may not be up.
> 
> Replace the netif_carrier_on(), netif_carrier_off() and
> stmmac_mac_set() calls with the appropriate phylink_start() and
> phylink_stop() calls, thereby allowing phylink to manage the netif
> carrier and TE/RE bits through the .mac_link_up() and .mac_link_down()
> methods.
> 
> Note that RE should only be set after the DMA is ready to avoid the
> receive FIFO between the MAC and DMA blocks overflowing, so
> phylink_start() needs to be placed after DMA has been started.
> 
> Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 14 ++++++--------
>  1 file changed, 6 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 13796b1c8d7c..84d8b1c9f6d4 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -6887,6 +6887,8 @@ void stmmac_xdp_release(struct net_device *dev)
>  	/* Ensure tx function is not running */
>  	netif_tx_disable(dev);
>  
> +	phylink_stop(priv->phylink);
> +
>  	/* Disable NAPI process */
>  	stmmac_disable_all_queues(priv);
>  
> @@ -6902,14 +6904,10 @@ void stmmac_xdp_release(struct net_device *dev)
>  	/* Release and free the Rx/Tx resources */
>  	free_dma_desc_resources(priv, &priv->dma_conf);
>  
> -	/* Disable the MAC Rx/Tx */
> -	stmmac_mac_set(priv, priv->ioaddr, false);
> -
>  	/* set trans_start so we don't get spurious
>  	 * watchdogs during reset
>  	 */
>  	netif_trans_update(dev);
> -	netif_carrier_off(dev);
>  }
>  
>  int stmmac_xdp_open(struct net_device *dev)
> @@ -6992,25 +6990,25 @@ int stmmac_xdp_open(struct net_device *dev)
>  		tx_q->txtimer.function = stmmac_tx_timer;
>  	}
>  
> -	/* Enable the MAC Rx/Tx */
> -	stmmac_mac_set(priv, priv->ioaddr, true);
> -
>  	/* Start Rx & Tx DMA Channels */
>  	stmmac_start_all_dma(priv);
>  
> +	phylink_start(priv->phylink);
> +
>  	ret = stmmac_request_irq(dev);
>  	if (ret)
>  		goto irq_error;
>  
>  	/* Enable NAPI process*/
>  	stmmac_enable_all_queues(priv);
> -	netif_carrier_on(dev);
>  	netif_tx_start_all_queues(dev);
>  	stmmac_enable_all_dma_irq(priv);
>  
>  	return 0;
>  
>  irq_error:
> +	phylink_stop(priv->phylink);
> +
>  	for (chan = 0; chan < priv->plat->tx_queues_to_use; chan++)
>  		hrtimer_cancel(&priv->dma_conf.tx_queue[chan].txtimer);
>  

XDP programs work like a charm both before and after this patch.

Tested-by: Furong Xu <0x1207@gmail.com>