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Subject: Re: [PATCH 2/2] net: dsa: qca8k: Improve SGMII interface handling
To:     Jonathan McDowell <noodles@earth.li>,
        Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc:     Andrew Lunn <andrew@lunn.ch>,
        Vivien Didelot <vivien.didelot@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <cover.1591816172.git.noodles@earth.li>
 <2150f4c70c754aed179e46e166f3c305254cf85a.1591816172.git.noodles@earth.li>
From:   Florian Fainelli <f.fainelli@gmail.com>
Message-ID: <9d7d09d5-393f-d5bd-5c57-78c914bdc850@gmail.com>
Date:   Wed, 10 Jun 2020 20:31:11 -0700
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On 6/10/2020 12:15 PM, Jonathan McDowell wrote:
> This patch improves the handling of the SGMII interface on the QCA8K
> devices. Previously the driver did no configuration of the port, even if
> it was selected. We now configure it up in the appropriate
> PHY/MAC/Base-X mode depending on what phylink tells us we are connected
> to and ensure it is enabled.
> 
> Tested with a device where the CPU connection is RGMII (i.e. the common
> current use case) + one where the CPU connection is SGMII. I don't have
> any devices where the SGMII interface is brought out to something other
> than the CPU.
> 
> Signed-off-by: Jonathan McDowell <noodles@earth.li>
> ---
>  drivers/net/dsa/qca8k.c | 28 +++++++++++++++++++++++++++-
>  drivers/net/dsa/qca8k.h | 13 +++++++++++++
>  2 files changed, 40 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/dsa/qca8k.c b/drivers/net/dsa/qca8k.c
> index dcd9e8fa99b6..33e62598289e 100644
> --- a/drivers/net/dsa/qca8k.c
> +++ b/drivers/net/dsa/qca8k.c
> @@ -681,7 +681,7 @@ qca8k_phylink_mac_config(struct dsa_switch *ds, int port, unsigned int mode,
>  			 const struct phylink_link_state *state)
>  {
>  	struct qca8k_priv *priv = ds->priv;
> -	u32 reg;
> +	u32 reg, val;
>  
>  	switch (port) {
>  	case 0: /* 1st CPU port */
> @@ -740,6 +740,32 @@ qca8k_phylink_mac_config(struct dsa_switch *ds, int port, unsigned int mode,
>  	case PHY_INTERFACE_MODE_1000BASEX:
>  		/* Enable SGMII on the port */
>  		qca8k_write(priv, reg, QCA8K_PORT_PAD_SGMII_EN);
> +
> +		/* Enable/disable SerDes auto-negotiation as necessary */
> +		val = qca8k_read(priv, QCA8K_REG_PWS);
> +		if (phylink_autoneg_inband(mode))
> +			val &= ~QCA8K_PWS_SERDES_AEN_DIS;
> +		else
> +			val |= QCA8K_PWS_SERDES_AEN_DIS;
> +		qca8k_write(priv, QCA8K_REG_PWS, val);
> +
> +		/* Configure the SGMII parameters */
> +		val = qca8k_read(priv, QCA8K_REG_SGMII_CTRL);
> +
> +		val |= QCA8K_SGMII_EN_PLL | QCA8K_SGMII_EN_RX |
> +			QCA8K_SGMII_EN_TX | QCA8K_SGMII_EN_SD;
> +
> +		val &= ~QCA8K_SGMII_MODE_CTRL_MASK;
> +		if (dsa_is_cpu_port(ds, port)) {
> +			/* CPU port, we're talking to the CPU MAC, be a PHY */
> +			val |= QCA8K_SGMII_MODE_CTRL_PHY;

Since port 6 can be interfaced to an external PHY, do not you have to
differentiate here whether this port is connected to an actual PHY,
versus connected to a MAC? You should be able to use mode == MLO_AN_PHY
to differentiate that case from the others.

> +		} else if (state->interface == PHY_INTERFACE_MODE_SGMII) {
> +			val |= QCA8K_SGMII_MODE_CTRL_MAC;
> +		} else {
> +			val |= QCA8K_SGMII_MODE_CTRL_BASEX;

Better make this explicit and check for PHY_INTERFACE_MODE_1000BASEX,
even if those are the only two possible values covered by this part of
the case statement.
-- 
Florian