Hi Michal,

On Wed, Apr 29, 2020 at 09:52:22PM +0200, Michal Kubecek wrote:

On Tue, Apr 28, 2020 at 09:53:07AM +0200, Oleksij Rempel wrote:

quoted

This UAPI is needed for BroadR-Reach 100BASE-T1 devices. Due to lack of
auto-negotiation support, we needed to be able to configure the
MASTER-SLAVE role of the port manually or from an application in user
space.

The same UAPI can be used for 1000BASE-T or MultiGBASE-T devices to
force MASTER or SLAVE role. See IEEE 802.3-2018:
22.2.4.3.7 MASTER-SLAVE control register (Register 9)
22.2.4.3.8 MASTER-SLAVE status register (Register 10)
40.5.2 MASTER-SLAVE configuration resolution
45.2.1.185.1 MASTER-SLAVE config value (1.2100.14)
45.2.7.10 MultiGBASE-T AN control 1 register (Register 7.32)

The MASTER-SLAVE role affects the clock configuration:

-------------------------------------------------------------------------------
When the  PHY is configured as MASTER, the PMA Transmit function shall
source TX_TCLK from a local clock source. When configured as SLAVE, the
PMA Transmit function shall source TX_TCLK from the clock recovered from
data stream provided by MASTER.

iMX6Q                     KSZ9031                XXX
------\                /-----------\        /------------\
      |                |           |        |            |
 MAC  |<----RGMII----->| PHY Slave |<------>| PHY Master |
      |<--- 125 MHz ---+-<------/  |        | \          |
------/                \-----------/        \------------/
                                               ^
                                                \-TX_TCLK

-------------------------------------------------------------------------------

Since some clock or link related issues are only reproducible in a
specific MASTER-SLAVE-role, MAC and PHY configuration, it is beneficial
to provide generic (not 100BASE-T1 specific) interface to the user space
for configuration flexibility and trouble shooting.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
---

[...]

quoted

diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index 72c69a9c8a98a..a6a774beb2f90 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c

@@ -285,6 +285,9 @@ int phy_ethtool_ksettings_set(struct phy_device *phydev,
 	      duplex != DUPLEX_FULL)))
 		return -EINVAL;
 
+	if (!ethtool_validate_master_slave_cfg(cmd->base.master_slave_cfg))
+		return -EINVAL;
+

Unless we can/want to pass extack down here, I would prefer to have the
sanity check in ethtool_update_linkmodes() or ethtool_set_linkmodes() so
that we can set meaningful error message and offending attribute in
extack. (It could be even part of the policy.) Also, with the check only
here, drivers/devices not calling phy_ethtool_set_link_ksettings()
(directly or via phy_ethtool_set_link_ksettings()) and not handling the
new members themselves would silently ignore any value from userspace.

ok

quoted

 	phydev->autoneg = autoneg;
 
 	phydev->speed = speed;

[...]

quoted

+static int genphy_setup_master_slave(struct phy_device *phydev)
+{
+	u16 ctl = 0;
+
+	if (!phydev->is_gigabit_capable)
+		return 0;

Shouldn't we rather return -EOPNOTSUPP if value different from
CFG_UNKNOWN was requested?

sounds plausible.

quoted

+
+	switch (phydev->master_slave_set) {
+	case PORT_MODE_CFG_MASTER_PREFERRED:
+		ctl |= CTL1000_PREFER_MASTER;
+		break;
+	case PORT_MODE_CFG_SLAVE_PREFERRED:
+		break;
+	case PORT_MODE_CFG_MASTER_FORCE:
+		ctl |= CTL1000_AS_MASTER;
+		/* fallthrough */
+	case PORT_MODE_CFG_SLAVE_FORCE:
+		ctl |= CTL1000_ENABLE_MASTER;
+		break;
+	case PORT_MODE_CFG_UNKNOWN:
+		return 0;
+	default:
+		phydev_warn(phydev, "Unsupported Master/Slave mode\n");
+		return 0;
+	}

[...]

quoted

diff --git a/include/uapi/linux/ethtool.h b/include/uapi/linux/ethtool.h
index 92f737f101178..eb680e3d6bda5 100644
--- a/include/uapi/linux/ethtool.h
+++ b/include/uapi/linux/ethtool.h

@@ -1666,6 +1666,31 @@ static inline int ethtool_validate_duplex(__u8 duplex)
 	return 0;
 }
 
+/* Port mode */
+#define PORT_MODE_CFG_UNKNOWN		0
+#define PORT_MODE_CFG_MASTER_PREFERRED	1
+#define PORT_MODE_CFG_SLAVE_PREFERRED	2
+#define PORT_MODE_CFG_MASTER_FORCE	3
+#define PORT_MODE_CFG_SLAVE_FORCE	4
+#define PORT_MODE_STATE_UNKNOWN		0
+#define PORT_MODE_STATE_MASTER		1
+#define PORT_MODE_STATE_SLAVE		2
+#define PORT_MODE_STATE_ERR		3

You have "MASTER_SLAVE" or "master_slave" everywhere but "PORT_MODE" in
these constants which is inconsistent.

What will be preferred name?

quoted

+
+static inline int ethtool_validate_master_slave_cfg(__u8 cfg)
+{
+	switch (cfg) {
+	case PORT_MODE_CFG_MASTER_PREFERRED:
+	case PORT_MODE_CFG_SLAVE_PREFERRED:
+	case PORT_MODE_CFG_MASTER_FORCE:
+	case PORT_MODE_CFG_SLAVE_FORCE:
+	case PORT_MODE_CFG_UNKNOWN:
+		return 1;
+	}
+
+	return 0;
+}

Should we really allow CFG_UNKNOWN in client requests? As far as I can
see, this value is handled as no-op which should be rather expressed by
absence of the attribute. Allowing the client to request a value,
keeping current one and returning 0 (success) is IMHO wrong.

ok

Also, should this function be in UAPI header?

It is placed together with other validate functions:
ethtool_validate_duplex
ethtool_validate_speed

Doing it in a different place, would be inconsistent.

[...]

quoted

@@ -119,7 +123,12 @@ static int linkmodes_fill_reply(struct sk_buff *skb,
 	}
 
 	if (nla_put_u32(skb, ETHTOOL_A_LINKMODES_SPEED, lsettings->speed) ||
-	    nla_put_u8(skb, ETHTOOL_A_LINKMODES_DUPLEX, lsettings->duplex))
+	    nla_put_u8(skb, ETHTOOL_A_LINKMODES_DUPLEX, lsettings->duplex) ||
+	    nla_put_u8(skb, ETHTOOL_A_LINKMODES_MASTER_SLAVE_CFG,
+		       lsettings->master_slave_cfg) ||
+	    nla_put_u8(skb, ETHTOOL_A_LINKMODES_MASTER_SLAVE_STATE,
+		       lsettings->master_slave_state))
+
 		return -EMSGSIZE;

From the two handlers you introduced, it seems we only get CFG_UNKNOWN
or STATE_UNKNOWN if driver or device does not support the feature at all
so it would be IMHO more appropriate to omit the attribute in such case.

STATE_UNKNOWN is returned if link is not active.

Regards,
Oleksij
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