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Date: Thu, 30 Apr 2020 07:00:58 +0200
From: Oleksij Rempel <o.rempel@...gutronix.de>
To: Michal Kubecek <mkubecek@...e.cz>
Cc: Andrew Lunn <andrew@...n.ch>,
"David S. Miller" <davem@...emloft.net>,
Florian Fainelli <f.fainelli@...il.com>,
Heiner Kallweit <hkallweit1@...il.com>,
Jakub Kicinski <kuba@...nel.org>,
Jonathan Corbet <corbet@....net>,
David Jander <david@...tonic.nl>, kernel@...gutronix.de,
linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
Russell King <linux@...linux.org.uk>, mkl@...gutronix.de,
Marek Vasut <marex@...x.de>,
Christian Herber <christian.herber@....com>
Subject: Re: [PATCH net-next v3 1/2] ethtool: provide UAPI for PHY
master/slave configuration.
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:
> > 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@...gutronix.de>
> > ---
> [...]
> > 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
> > phydev->autoneg = autoneg;
> >
> > phydev->speed = speed;
> [...]
> > +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.
> > +
> > + 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;
> > + }
> [...]
> > 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?
> > +
> > +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.
> [...]
> > @@ -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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