Re: [PATCH net-next v3 03/10] net: sparx5: add hostmode with phylink support

[Steen Hegelund <steen.hegelund@microchip.com>]

Hi Russell,

Thanks for your comments.

On Mon, 2021-06-07 at 10:15 +0100, Russell King (Oracle) wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> On Fri, Jun 04, 2021 at 10:55:53AM +0200, Steen Hegelund wrote:
> > +static void sparx5_phylink_mac_config(struct phylink_config *config,
> > +                                   unsigned int mode,
> > +                                   const struct phylink_link_state *state)
> > +{
> > +     struct sparx5_port *port = netdev_priv(to_net_dev(config->dev));
> > +     struct sparx5_port_config conf;
> > +
> > +     conf = port->conf;
> > +     conf.power_down = false;
> > +     conf.portmode = state->interface;
> > +     conf.speed = state->speed;
> > +     conf.autoneg = state->an_enabled;
> > +     conf.pause = state->pause;
> > +
> > +     if (state->interface == PHY_INTERFACE_MODE_10GBASER) {
> > +             if (state->speed == SPEED_UNKNOWN) {
> > +                     /* When a SFP is plugged in we use capabilities to
> > +                      * default to the highest supported speed
> > +                      */
> > +                     if (phylink_test(state->advertising, 25000baseSR_Full) ||
> > +                         phylink_test(state->advertising, 25000baseCR_Full))
> > +                             conf.speed = SPEED_25000;
> > +                     else if (state->interface == PHY_INTERFACE_MODE_10GBASER)
> > +                             conf.speed = SPEED_10000;
> > +             } else if (state->speed == SPEED_2500) {
> > +                     conf.portmode = PHY_INTERFACE_MODE_2500BASEX;
> > +             } else if (state->speed == SPEED_1000) {
> > +                     conf.portmode = PHY_INTERFACE_MODE_1000BASEX;
> > +             }
> 
> 1) As detailed in the documentation for phylink, state->speed is not
>    guaranteed to be valid in the mac_config method.

OK.  I will assume speed is not known in this callback.


> 2) We clearly need PHY_INTERFACE_MODE_25GBASER rather than working
>    around this by testing bits in the advertising bitmap.


Yes that would be a very useful addition.
Should I add PHY_INTERFACE_MODE_25GBASER in this series or should that be added as a separate
series?

> 
> 3) I really don't get what's going on with setting the port mode to
>    2500base-X and 1000base-X here when state->interface is 10GBASER.

The high speed interfaces (> 2.5G) do not support any in-band signalling, so the only way that e.g a
10G interface running at 2.5G will be able to link up with its partner is if both ends configure the
speed manually via ethtool.
	
> 
> > +             if (phylink_test(state->advertising, FIBRE))
> > +                     conf.media = PHY_MEDIA_SR;
> > +             else
> > +                     conf.media = PHY_MEDIA_DAC;
> > +     }
> > +
> > +     if (!port_conf_has_changed(&port->conf, &conf))
> > +             return;
> > +}
> > +
> > +static void sparx5_phylink_mac_link_up(struct phylink_config *config,
> > +                                    struct phy_device *phy,
> > +                                    unsigned int mode,
> > +                                    phy_interface_t interface,
> > +                                    int speed, int duplex,
> > +                                    bool tx_pause, bool rx_pause)
> > +{
> 
> This is the only place that the MAC is guaranteed to know the
> negotiated speed.

OK.

> 
> --
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
> FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!


-- 
BR
Steen

-=-=-=-=-=-=-=-=-=-=-=-=-=-=
steen.hegelund@microchip.com