netdev - RE: [PATCH net-next v2 3/3] dpaa2-eth: Add pause frame support

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Date:   Wed, 28 Aug 2019 08:40:29 +0000
From:   Ioana Ciocoi Radulescu <ruxandra.radulescu@....com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        Ioana Ciornei <ioana.ciornei@....com>
Subject: RE: [PATCH net-next v2 3/3] dpaa2-eth: Add pause frame support

> -----Original Message-----
> From: Andrew Lunn <andrew@...n.ch>
> Sent: Wednesday, August 28, 2019 2:22 AM
> To: Ioana Ciocoi Radulescu <ruxandra.radulescu@....com>
> Cc: netdev@...r.kernel.org; davem@...emloft.net; Ioana Ciornei
> <ioana.ciornei@....com>
> Subject: Re: [PATCH net-next v2 3/3] dpaa2-eth: Add pause frame support
> 
> On Tue, Aug 27, 2019 at 05:15:51PM +0300, Ioana Radulescu wrote:
> > Starting with firmware version MC10.18.0, we have support for
> > L2 flow control. Asymmetrical configuration (Rx or Tx only) is
> > supported, but not pause frame autonegotioation.
> 
> > +static int set_pause(struct dpaa2_eth_priv *priv)
> > +{
> > +	struct device *dev = priv->net_dev->dev.parent;
> > +	struct dpni_link_cfg link_cfg = {0};
> > +	int err;
> > +
> > +	/* Get the default link options so we don't override other flags */
> > +	err = dpni_get_link_cfg(priv->mc_io, 0, priv->mc_token, &link_cfg);
> > +	if (err) {
> > +		dev_err(dev, "dpni_get_link_cfg() failed\n");
> > +		return err;
> > +	}
> > +
> > +	link_cfg.options |= DPNI_LINK_OPT_PAUSE;
> > +	link_cfg.options &= ~DPNI_LINK_OPT_ASYM_PAUSE;
> > +	err = dpni_set_link_cfg(priv->mc_io, 0, priv->mc_token, &link_cfg);
> > +	if (err) {
> > +		dev_err(dev, "dpni_set_link_cfg() failed\n");
> > +		return err;
> > +	}
> > +
> > +	priv->link_state.options = link_cfg.options;
> > +
> > +	return 0;
> > +}
> > +
> >  /* Configure the DPNI object this interface is associated with */
> >  static int setup_dpni(struct fsl_mc_device *ls_dev)
> >  {
> > @@ -2500,6 +2562,13 @@ static int setup_dpni(struct fsl_mc_device
> *ls_dev)
> >
> >  	set_enqueue_mode(priv);
> >
> > +	/* Enable pause frame support */
> > +	if (dpaa2_eth_has_pause_support(priv)) {
> > +		err = set_pause(priv);
> > +		if (err)
> > +			goto close;
> 
> Hi Ioana
> 
> So by default you have the MAC do pause, not asym pause?  Generally,
> any MAC that can do asym pause does asym pause.

Clearing the ASYM_PAUSE flag only means we tell the firmware we want
both Rx and Tx pause to be enabled in the beginning. User can still set
an asymmetric config (i.e. only Rx pause or only Tx pause to be enabled)
if needed.

The truth table is like this:

PAUSE | ASYM_PAUSE | Rx pause | Tx pause
----------------------------------------
  0   |     0      | disabled | disabled
  0   |     1      | disabled | enabled
  1   |     0      | enabled  | enabled
  1   |     1      | enabled  | disabled

Thanks,
Ioana