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SubjectRE: [PATCH net-next v6 6/6] dsa: lan9303: Migrate to PHYLINK
Date
> > +static void lan9303_phylink_get_caps(struct dsa_switch *ds, int port,
> > + struct phylink_config *config)
> > +{
> > + struct lan9303 *chip = ds->priv;
> > +
> > + dev_dbg(chip->dev, "%s(%d) entered.", __func__, port);
> > +
> > + config->mac_capabilities = MAC_10 | MAC_100 | MAC_ASYM_PAUSE |
> > + MAC_SYM_PAUSE;
>
> You indicate that pause modes are supported, but...
>
> > +static void lan9303_phylink_mac_link_up(struct dsa_switch *ds, int port,
> > + unsigned int mode,
> > + phy_interface_t interface,
> > + struct phy_device *phydev, int speed,
> > + int duplex, bool tx_pause,
> > + bool rx_pause)
> > +{
> > + u32 ctl;
> > +
> > + /* On this device, we are only interested in doing something here if
> > + * this is the xMII port. All other ports are 10/100 phys using MDIO
> > + * to control there link settings.
> > + */
> > + if (port != 0)
> > + return;
> > +
> > + ctl = lan9303_phy_read(ds, port, MII_BMCR);
> > +
> > + ctl &= ~BMCR_ANENABLE;
> > +
> > + if (speed == SPEED_100)
> > + ctl |= BMCR_SPEED100;
> > + else if (speed == SPEED_10)
> > + ctl &= ~BMCR_SPEED100;
> > + else
> > + dev_err(ds->dev, "unsupported speed: %d\n", speed);
> > +
> > + if (duplex == DUPLEX_FULL)
> > + ctl |= BMCR_FULLDPLX;
> > + else
> > + ctl &= ~BMCR_FULLDPLX;
> > +
> > + lan9303_phy_write(ds, port, MII_BMCR, ctl);
>
> There is no code here to program the resolved pause modes. Is it handled
> internally within the switch? (Please add a comment to this effect
> either in get_caps or here.)
>
> Thanks.
>

As I look into this, the part does have control flags for advertising
Symmetric and Asymmetric pause toward the link partner. The default is set
by a configuration strap on power-up. I am having trouble mapping the rx and
tx pause parameters into symmetric and asymmetric controls. Where can I find
the proper definitions and mappings?

ctl &= ~( ADVERTISE_PAUSE_CAP | ADVERTISE_PAUSE_AYM);
if(tx_pause)
ctl |= ADVERTISE_PAUSE_CAP;
if(rx_pause)
ctl |= ADVERTISE_PAUSE_AYM;

If I can pause my transmissions (receive pause requests), then advertise
symmetric whether I ever sent pause requests or not.
If I can send pause requests (using flow control on my receive side), then make
sure asymmetric support is also advertised as rx_pause might have been clear.
Not that if both rx and tx pause is supported, we can support either symmetric
or asymmetric operating modes.

If I receive a pause request, it affects my transmit data flow. So one could
argue the rx_pause flag controls my ability to receive pause requests. I tend
to overthink and almost always get these 50/50 propositions wrong.

Regards,
Jerry

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