linux-kernel - Re: [PATCH RFC net-next 14/19] net: mvpp2: add ethtool flow control configuration support

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Message-ID: <X/s6bkkoq4HVbLR+@lunn.ch>
Date:   Sun, 10 Jan 2021 18:33:34 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     stefanc@...vell.com
Cc:     netdev@...r.kernel.org, thomas.petazzoni@...tlin.com,
        davem@...emloft.net, nadavh@...vell.com, ymarkman@...vell.com,
        linux-kernel@...r.kernel.org, kuba@...nel.org,
        linux@...linux.org.uk, mw@...ihalf.com, rmk+kernel@...linux.org.uk,
        atenart@...nel.org
Subject: Re: [PATCH RFC net-next  14/19] net: mvpp2: add ethtool flow control
 configuration support

> @@ -5373,6 +5402,30 @@ static int mvpp2_ethtool_set_pause_param(struct net_device *dev,
>  					 struct ethtool_pauseparam *pause)
>  {
>  	struct mvpp2_port *port = netdev_priv(dev);
> +	int i;
> +
> +	if (pause->tx_pause && port->priv->global_tx_fc) {
> +		port->tx_fc = true;
> +		mvpp2_rxq_enable_fc(port);
> +		if (port->priv->percpu_pools) {
> +			for (i = 0; i < port->nrxqs; i++)
> +				mvpp2_bm_pool_update_fc(port, &port->priv->bm_pools[i], true);
> +		} else {
> +			mvpp2_bm_pool_update_fc(port, port->pool_long, true);
> +			mvpp2_bm_pool_update_fc(port, port->pool_short, true);
> +		}
> +
> +	} else if (port->priv->global_tx_fc) {
> +		port->tx_fc = false;
> +		mvpp2_rxq_disable_fc(port);
> +		if (port->priv->percpu_pools) {
> +			for (i = 0; i < port->nrxqs; i++)
> +				mvpp2_bm_pool_update_fc(port, &port->priv->bm_pools[i], false);
> +		} else {
> +			mvpp2_bm_pool_update_fc(port, port->pool_long, false);
> +			mvpp2_bm_pool_update_fc(port, port->pool_short, false);
> +		}
> +	}


This looks wrong. Flow control is normally the result of auto
negotiation. Both ends need to agree to it. Which is why
mvpp2_ethtool_set_pause_param() passes the users request onto phylink.
phylink will handle the autoneg and then ask the MAC to setup flow
control depending on the result in mvpp2_mac_link_up().

	Andrew