Re: [RFC PATCH 2/3] net: sparx5: Add Sparx5 switchdev driver

[Steen Hegelund]

On 29.11.2020 10:52, Russell King - ARM Linux admin wrote:
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> On Sat, Nov 28, 2020 at 10:28:28PM +0000, Russell King - ARM Linux admin wrote:
> > On Sat, Nov 28, 2020 at 08:06:16PM +0100, Andrew Lunn 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;
> > > > + int err = 0;
> > > > +
> > > > + conf = port->conf;
> > > > + conf.autoneg = state->an_enabled;
> > > > + conf.pause = state->pause;
> > > > + conf.duplex = state->duplex;
> > > > + conf.power_down = false;
> > > > + conf.portmode = state->interface;
> > > > +
> > > > + if (state->speed == SPEED_UNKNOWN) {
> > > > +         /* When a SFP is plugged in we use capabilities to
> > > > +          * default to the highest supported speed
> > > > +          */
> > >
> > > This looks suspicious.
> >
> > Yes, it looks highly suspicious. The fact that
> > sparx5_phylink_mac_link_up() is empty, and sparx5_phylink_mac_config()
> > does all the work suggests that this was developed before the phylink
> > re-organisation, and this code hasn't been updated for it.
> >
> > Any new code for the kernel really ought to be updated for the new
> > phylink methodology before it is accepted.
> >
> > Looking at sparx5_port_config(), it also seems to use
> > PHY_INTERFACE_MODE_1000BASEX for both 1000BASE-X and 2500BASE-X. All
> > very well for the driver to do that internally, but it's confusing
> > when it comes to reviewing this stuff, especially when people outside
> > of the driver (such as myself) reviewing it need to understand what's
> > going on with the configuration.

Hi Russell,

> There are other issues too.
>
> Looking at sparx5_get_1000basex_status(), we have:
>
> +       status->link = DEV2G5_PCS1G_LINK_STATUS_LINK_STATUS_GET(value) |
> +                      DEV2G5_PCS1G_LINK_STATUS_SYNC_STATUS_GET(value);

> Why is the link status the logical OR of these?

Oops: It should have been AND. Well spotted.

> +                       if ((lp_abil >> 8) & 1) /* symmetric pause */
> +                               status->pause = MLO_PAUSE_RX | MLO_PAUSE_TX;
> +                       if (lp_abil & (1 << 7)) /* asymmetric pause */
> +                               status->pause |= MLO_PAUSE_RX;
>
> is actually wrong, and I see I need to improve the documentation for
> mac_pcs_get_state(). The intention in the documentation was concerning
> hardware that indicated the _resolved_ status of pause modes. It was
> not intended that drivers resolve the pause modes themselves.
>
> Even so, the above is still wrong; it takes no account of what is being
> advertised at the local end. If one looks at the implementation in
> phylink_decode_c37_word(), one will notice there is code to deal with
> this.
>
> I think we ought to make phylink_decode_c37_word() and
> phylink_decode_sgmii_word() public functions, and then this driver can
> use these helpers to decode the link partner advertisement to the
> phylink state.

Should I remove the current implementation and use something like what
is in phylink_decode_c37_word() and phylink_decode_sgmii_word() in the
meantime?

> Does the driver need to provide an ethtool .get_link function? That
> seems to bypass phylink. Why can't ethtool_op_get_link() be used?

I think that I tried that earlier, but ran into problems.  I better
revisit this, and try out your suggestion.

> I think if ethtool_op_get_link() is used, we then have just one caller
> for sparx5_get_port_status(), which means "struct sparx5_port_status"
> can be eliminated and the code cleaned up to use the phylink decoding
> helpers.
>
> --
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Thanks for your comments.

BR
Steen

---------------------------------------
Steen Hegelund
steen.hegelund@xxxxxxxxxxxxx