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

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Message-ID: <CO6PR18MB3873D0FCB65F1E3879002D15B0AC9@CO6PR18MB3873.namprd18.prod.outlook.com>
Date:   Sun, 10 Jan 2021 18:27:57 +0000
From:   Stefan Chulski <stefanc@...vell.com>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "thomas.petazzoni@...tlin.com" <thomas.petazzoni@...tlin.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        Nadav Haklai <nadavh@...vell.com>,
        Yan Markman <ymarkman@...vell.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "mw@...ihalf.com" <mw@...ihalf.com>,
        "andrew@...n.ch" <andrew@...n.ch>,
        "atenart@...nel.org" <atenart@...nel.org>
Subject: RE: [EXT] 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 doesn't look correct to me. This function is only called when ethtool -A is
> used to change the flow control settings. This is not the place to be
> configuring flow control, as flow control is negotiated with the link partner.
> 
> The final resolved flow control settings are available in
> mvpp2_mac_link_up() via the tx_pause and rx_pause parameters.

I would move this to mvpp2_mac_link_up.
Thanks.
 
> What also concerns me is whether flow control is supported in the existing
> driver at all, given this patch set. If it isn't supported without the firmware's
> help, then we should _not_ be negotiating flow control with the link partner
> unless we actually support it, so the Pause and Asym_Pause bits in
> mvpp2_phylink_validate() should be cleared.

RX FC supported, issue only with TX FC.

Stefan,
Regards.