Re: [PATCH v5 1/2] ethtool: provide UAPI for PHY master/slave configuration.

From: Oleksij Rempel
Date: Mon May 04 2020 - 06:10:41 EST

On Mon, May 04, 2020 at 11:10:44AM +0200, Michal Kubecek wrote:
> On Mon, May 04, 2020 at 09:12:13AM +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@xxxxxxxxxxxxxx>
> > ---
> > diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> > index ac2784192472f..42dda9d2082ee 100644
> > --- a/drivers/net/phy/phy_device.c
> > +++ b/drivers/net/phy/phy_device.c
> > @@ -1768,6 +1768,90 @@ int genphy_setup_forced(struct phy_device *phydev)
> > }
> > EXPORT_SYMBOL(genphy_setup_forced);
> >
> > +static int genphy_setup_master_slave(struct phy_device *phydev)
> > +{
> > + u16 ctl = 0;
> > +
> > + if (!phydev->is_gigabit_capable)
> > + return 0;
>
> Why did you revert to silently ignoring requests in this case?

genphy_setup_forced() is called by __genphy_config_aneg() and this can
be called by a PHY driver after configuring master slave mode locally by
PHY driver. See tja11xx patch. Same can be potentially done in the phy/realtek.c
driver.

Currently my imagination is not caffeanized enough to
provide a better solution. Do you have ideas?

> On the
> other hand, we might rather want to do a more generic check which would
> handle all drivers not supporting the feature, see below.

> [...]
> > @@ -287,14 +308,37 @@ static bool ethnl_auto_linkmodes(struct ethtool_link_ksettings *ksettings,
> > __ETHTOOL_LINK_MODE_MASK_NBITS);
> > }
> >
> > +static int ethnl_validate_master_slave_cfg(u8 cfg)
> > +{
> > + switch (cfg) {
> > + case MASTER_SLAVE_CFG_MASTER_PREFERRED:
> > + case MASTER_SLAVE_CFG_SLAVE_PREFERRED:
> > + case MASTER_SLAVE_CFG_MASTER_FORCE:
> > + case MASTER_SLAVE_CFG_SLAVE_FORCE:
> > + return 1;
> > + }
> > +
> > + return 0;
> > +}
>
> Nitpick: bool would be more appropriate as return value.

ok

> > +
> > static int ethnl_update_linkmodes(struct genl_info *info, struct nlattr **tb,
> > struct ethtool_link_ksettings *ksettings,
> > bool *mod)
> > {
> > struct ethtool_link_settings *lsettings = &ksettings->base;
> > bool req_speed, req_duplex;
> > + const struct nlattr *master_slave_cfg;
> > int ret;
> >
> > + master_slave_cfg = tb[ETHTOOL_A_LINKMODES_MASTER_SLAVE_CFG];
> > + if (master_slave_cfg) {
> > + u8 cfg = nla_get_u8(master_slave_cfg);
> > + if (!ethnl_validate_master_slave_cfg(cfg)) {
> > + GENL_SET_ERR_MSG(info, "LINKMODES_MASTER_SLAVE_CFG contains not valid value");
> > + return -EOPNOTSUPP;
> > + }
> > + }
>
> Please set also the "bad attribute" in extack, it may help
> non-interactive clients.
>
> Also, it would be nice to report error if client wants to set master/slave but
> driver does not support it. How about this?
>
> if (master_slave_cfg) {
> u8 cfg = nla_get_u8(master_slave_cfg);
>
> if (lsettings->master_slave_cfg == MASTER_SLAVE_CFG_UNSUPPORTED) {
> NL_SET_ERR_MSG_ATTR(info->extack, master_slave_cfg,
> "master/slave configuration not supported by device");
> return -EOPNOTSUPP;
> }
> if (!ethnl_validate_master_slave_cfg(cfg)) {
> NL_SET_ERR_MSG_ATTR(info->extack, master_slave_cfg,
> "master/slave value is invalid");
> return -EOPNOTSUPP;
> }
> }
>

looks good. thx!

>
> Do you plan to allow handling master/slave also via ioctl()?

no.

> If yes, we should
> also add the sanity checks to ioctl code path. If not, we should prevent
> passing non-zero values from userspace to driver.

What is the best place to add this sanity check?

> Other than this, the patch looks good to me.
>
> Michal
>
> > *mod = false;
> > req_speed = tb[ETHTOOL_A_LINKMODES_SPEED];
> > req_duplex = tb[ETHTOOL_A_LINKMODES_DUPLEX];
> > @@ -311,6 +355,7 @@ static int ethnl_update_linkmodes(struct genl_info *info, struct nlattr **tb,
> > mod);
> > ethnl_update_u8(&lsettings->duplex, tb[ETHTOOL_A_LINKMODES_DUPLEX],
> > mod);
> > + ethnl_update_u8(&lsettings->master_slave_cfg, master_slave_cfg, mod);
> >
> > if (!tb[ETHTOOL_A_LINKMODES_OURS] && lsettings->autoneg &&
> > (req_speed || req_duplex) &&
> > --
> > 2.26.2
> >
>
>

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