netdev - Re: [PATCH net 2/3] net: mediatek: sgmii: autonegotiation is required

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Date:   Thu, 19 Jan 2023 20:33:17 +0100
From:   Bjørn Mork <bjorn@...k.no>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     netdev@...r.kernel.org, Felix Fietkau <nbd@....name>,
        John Crispin <john@...ozen.org>,
        Sean Wang <sean.wang@...iatek.com>,
        Mark Lee <Mark-MC.Lee@...iatek.com>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Daniel Golle <daniel@...rotopia.org>,
        Alexander Couzens <lynxis@...0.eu>
Subject: Re: [PATCH net 2/3] net: mediatek: sgmii: autonegotiation is required

"Russell King (Oracle)" <linux@...linux.org.uk> writes:
> On Thu, Jan 19, 2023 at 06:12:47PM +0100, Bjørn Mork wrote:
>> sgmii mode fails if autonegotiation is disabled.
>> 
>> Signed-off-by: Bjørn Mork <bjorn@...k.no>
>> ---
>>  drivers/net/ethernet/mediatek/mtk_sgmii.c | 11 +++--------
>>  1 file changed, 3 insertions(+), 8 deletions(-)
>> 
>> diff --git a/drivers/net/ethernet/mediatek/mtk_sgmii.c b/drivers/net/ethernet/mediatek/mtk_sgmii.c
>> index 481f2f1e39f5..d1f2bcb21242 100644
>> --- a/drivers/net/ethernet/mediatek/mtk_sgmii.c
>> +++ b/drivers/net/ethernet/mediatek/mtk_sgmii.c
>> @@ -62,14 +62,9 @@ static int mtk_pcs_config(struct phylink_pcs *pcs, unsigned int mode,
>>  	 * other words, 1000Mbps or 2500Mbps).
>>  	 */
>>  	if (interface == PHY_INTERFACE_MODE_SGMII) {
>> -		sgm_mode = SGMII_IF_MODE_SGMII;
>> -		if (phylink_autoneg_inband(mode)) {
>> -			sgm_mode |= SGMII_REMOTE_FAULT_DIS |
>> -				    SGMII_SPEED_DUPLEX_AN;
>> -			use_an = true;
>> -		} else {
>> -			use_an = false;
>> -		}
>> +		sgm_mode = SGMII_IF_MODE_SGMII | SGMII_REMOTE_FAULT_DIS |
>> +			   SGMII_SPEED_DUPLEX_AN;
>> +		use_an = true;
>
> I wasn't actually suggesting in our discussion that this is something
> which should be changed.
>
> The reference implementation for the expected behaviour is
> phylink_mii_c22_pcs_config(), and it only enables in-band if "mode"
> says so. If we have a PHY which has in-band disabled (yes, they do
> exist) then having SGMII in-band unconditionally enabled breaks them,
> and yes, those PHYs appear on SFP modules.
>
> The proper answer is to use 'managed = "in-band-status";' in your DT
> to have in-band used with SGMII.

Well, yeah, I'd love to.  But then I'm back to the drawing board without
a link.  That just doesn't work for me.

What I did here also reflects what I saw in the mt7530.c debug dumps,
and how I read that code:

static int mt7531_sgmii_setup_mode_an(struct mt7530_priv *priv, int port,
				      phy_interface_t interface)
{
	if (!mt753x_is_mac_port(port))
		return -EINVAL;

	mt7530_set(priv, MT7531_QPHY_PWR_STATE_CTRL(port),
		   MT7531_SGMII_PHYA_PWD);

	mt7530_rmw(priv, MT7531_PHYA_CTRL_SIGNAL3(port),
		   MT7531_RG_TPHY_SPEED_MASK, MT7531_RG_TPHY_SPEED_1_25G);

	mt7530_set(priv, MT7531_SGMII_MODE(port),
		   MT7531_SGMII_REMOTE_FAULT_DIS |
		   MT7531_SGMII_SPEED_DUPLEX_AN);

	mt7530_rmw(priv, MT7531_PCS_SPEED_ABILITY(port),
		   MT7531_SGMII_TX_CONFIG_MASK, 1);

	mt7530_set(priv, MT7531_PCS_CONTROL_1(port), MT7531_SGMII_AN_ENABLE);

	mt7530_set(priv, MT7531_PCS_CONTROL_1(port), MT7531_SGMII_AN_RESTART);

	mt7530_write(priv, MT7531_QPHY_PWR_STATE_CTRL(port), 0);

	return 0;
}

static int
mt7531_mac_config(struct dsa_switch *ds, int port, unsigned int mode,
		  phy_interface_t interface)
{
	struct mt7530_priv *priv = ds->priv;
	struct phy_device *phydev;
	struct dsa_port *dp;

	if (!mt753x_is_mac_port(port)) {
		dev_err(priv->dev, "port %d is not a MAC port\n", port);
		return -EINVAL;
	}

	switch (interface) {
	case PHY_INTERFACE_MODE_RGMII:
	case PHY_INTERFACE_MODE_RGMII_ID:
	case PHY_INTERFACE_MODE_RGMII_RXID:
	case PHY_INTERFACE_MODE_RGMII_TXID:
		dp = dsa_to_port(ds, port);
		phydev = dp->slave->phydev;
		return mt7531_rgmii_setup(priv, port, interface, phydev);
	case PHY_INTERFACE_MODE_SGMII:
		return mt7531_sgmii_setup_mode_an(priv, port, interface);
	case PHY_INTERFACE_MODE_NA:
	case PHY_INTERFACE_MODE_1000BASEX:
	case PHY_INTERFACE_MODE_2500BASEX:
		return mt7531_sgmii_setup_mode_force(priv, port, interface);
	default:
		return -EINVAL;
	}

	return -EINVAL;
}


AFAICS, this calls mt7531_sgmii_setup_mode_an() unconditionally for
PHY_INTERFACE_MODE_SGMII. Resulting in AN_ENABLE|AN_RESTART being set in
PCS_CONTROL_1 and SGMII_REMOTE_FAULT_DIS|SGMII_SPEED_DUPLEX_AN being set
in SGMII_MODE.  Regardless of inband or not.



Bjørn