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

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Date:   Mon, 7 Jun 2021 10:15:36 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Steen Hegelund <steen.hegelund@...rochip.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, Andrew Lunn <andrew@...n.ch>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Madalin Bucur <madalin.bucur@....nxp.com>,
        Mark Einon <mark.einon@...il.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Simon Horman <simon.horman@...ronome.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Bjarni Jonasson <bjarni.jonasson@...rochip.com>,
        Lars Povlsen <lars.povlsen@...rochip.com>
Subject: Re: [PATCH net-next v3 03/10] net: sparx5: add hostmode with phylink
 support

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.

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

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.

> +		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.

-- 
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