linux-kernel - Re: [net-next PATCH v3 2/3] net: dsa: Add Airoha AN8855 5-Port Gigabit DSA Switch driver

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Message-ID: <Zy3tPeWCHOH-CMoy@shell.armlinux.org.uk>
Date: Fri, 8 Nov 2024 10:51:41 +0000
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Christian Marangi <ansuelsmth@...il.com>
Cc: Andrew Lunn <andrew@...n.ch>, Florian Fainelli <f.fainelli@...il.com>,
	Vladimir Oltean <olteanv@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org, netdev@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	upstream@...oha.com
Subject: Re: [net-next PATCH v3 2/3] net: dsa: Add Airoha AN8855 5-Port
 Gigabit DSA Switch driver

On Wed, Nov 06, 2024 at 01:22:37PM +0100, Christian Marangi wrote:
> +static int an8855_port_enable(struct dsa_switch *ds, int port,
> +			      struct phy_device *phy)
> +{
> +	int ret;
> +
> +	ret = an8855_port_set_status(ds->priv, port, true);
> +	if (ret)
> +		return ret;
> +
> +	if (dsa_is_user_port(ds, port))
> +		phy_support_asym_pause(phy);

This is unnecessary if you've set the phylink capabilities correctly
because phylink_bringup_phy() will setup the PHY accordingly.

> +static u32 en8855_get_phy_flags(struct dsa_switch *ds, int port)
> +{
> +	struct an8855_priv *priv = ds->priv;
> +
> +	/* PHY doesn't need calibration */
> +	if (!priv->phy_require_calib)
> +		return 0;
> +
> +	/* Use BIT(0) to signal calibration needed */
> +	return BIT(0);

This should be a #define somewhere that preferably includes the PHY
name so we have an idea in future which PHY driver is going to be
making use of this random bit.

> +static struct phylink_pcs *
> +an8855_phylink_mac_select_pcs(struct phylink_config *config,
> +			      phy_interface_t interface)
> +{
> +	struct dsa_port *dp = dsa_phylink_to_port(config);
> +	struct an8855_priv *priv = dp->ds->priv;
> +
> +	switch (interface) {
> +	case PHY_INTERFACE_MODE_SGMII:
> +	case PHY_INTERFACE_MODE_2500BASEX:
> +		return &priv->pcs;
> +	default:
> +		return NULL;
> +	}
> +}
> +
> +static void
> +an8855_phylink_mac_config(struct phylink_config *config, unsigned int mode,
> +			  const struct phylink_link_state *state)
> +{
> +	struct dsa_port *dp = dsa_phylink_to_port(config);
> +	struct dsa_switch *ds = dp->ds;
> +	struct an8855_priv *priv;
> +	int port = dp->index;
> +
> +	priv = ds->priv;
> +
> +	switch (port) {
> +	case 0:
> +	case 1:
> +	case 2:
> +	case 3:
> +	case 4:
> +		return;
> +	case 5:
> +		break;
> +	default:
> +		dev_err(ds->dev, "unsupported port: %d", port);
> +		return;
> +	}

	if (port != 5) {
		if (port > 5)
			dev_err(ds->dev, "unsupported port: %d", port);
		return;
	}

is simpler, no?

> +static int an8855_pcs_config(struct phylink_pcs *pcs, unsigned int neg_mode,
> +			     phy_interface_t interface,
> +			     const unsigned long *advertising,
> +			     bool permit_pause_to_mac)
> +{
> +	struct an8855_priv *priv = container_of(pcs, struct an8855_priv, pcs);
> +	u32 val;
> +	int ret;
> +
> +	switch (interface) {
> +	case PHY_INTERFACE_MODE_RGMII:
> +		return 0;

This shouldn't happen. First, in an8855_phylink_mac_select_pcs(), you
don't return a PCS in this mode. Second, phylink is highly unlikely to
switch from SGMII/2500baseX to RGMII mode. Third, in commit
486dc391ef43 ("net: phylink: allow mac_select_pcs() to remove a PCS")
will ensure that if phylink does do such a switch, because
an8855_phylink_mac_select_pcs() returns NULL for RGMII, these PCS
functions will never be called for RGMII modes.

Thanks.

-- 
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