Messages in this thread | | | Date | Fri, 17 Apr 2020 12:51:13 +0100 | From | Russell King - ARM Linux admin <> | Subject | Re: [PATCH v1] ethtool: provide UAPI for PHY master/slave configuration. |
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On Fri, Apr 17, 2020 at 01:28:30PM +0200, Oleksij Rempel wrote: > On Fri, Apr 17, 2020 at 11:11:45AM +0100, Russell King - ARM Linux admin wrote: > > On Wed, Apr 15, 2020 at 11:57:39PM +0200, Andrew Lunn wrote: > > > > diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c > > > > index c8b0c34030d32..d5edf2bc40e43 100644 > > > > --- a/drivers/net/phy/phy_device.c > > > > +++ b/drivers/net/phy/phy_device.c > > > > @@ -604,6 +604,7 @@ struct phy_device *phy_device_create(struct mii_bus *bus, int addr, u32 phy_id, > > > > dev->asym_pause = 0; > > > > dev->link = 0; > > > > dev->interface = PHY_INTERFACE_MODE_GMII; > > > > + dev->master_slave = PORT_MODE_UNKNOWN; > > > > > > phydev->master_slave is how we want the PHY to be configured. I don't > > > think PORT_MODE_UNKNOWN makes any sense in that contest. 802.3 gives > > > some defaults. 9.12 should be 0, meaning manual master/slave > > > configuration is disabled. The majority of linux devices are end > > > systems. So we should default to a single point device. So i would > > > initialise PORT_MODE_SLAVE, or whatever we end up calling that. > > > > I'm not sure that is a good idea given that we use phylib to drive > > the built-in PHYs in DSA switches, which ought to prefer master mode > > via the "is a multiport device" bit. > > > > Just to be clear, there are three bits that configure 1G PHYs, which > > I've framed in briefer terminology: > > > > - 9.12: auto/manual configuration (1= manual 0= slave) > > - 9.11: manual master/slave configuration (1= master, 0 = slave) > > - 9.10: auto master/slave preference (1= multiport / master) > > > > It is recommended that multiport devices (such as DSA switches) set > > 9.10 so they prefer to be master. > > > > It's likely that the reason is to reduce cross-talk interference > > between neighbouring ports both inside the PHY, magnetics and the > > board itself. I would suspect that this becomes critical when > > operating at towards the maximum cable length. > > > > I've checked some of my DSA switches, and 9.10 appears to default to > > one, as expected given what's in the specs. > > Hm.. > I've checked one of my DSA devices and 9.10 is by default 0 (proffered > slave). It get slave even if it is preferred master and it is > connected to a workstation (not multiport device) with a e1000e NIC. > The e1000e is configured by default as preferred master. > > Grepping over current linux kernel I see following attempts to > configure master/slave modes: > drivers/net/ethernet/intel/e1000e/phy.c:597 > e1000_set_master_slave_mode() > > all intel NICs have similar code code and do not touch preferred bit > 9.10. Only force master/slave modes. So the preferred master is probably > PHY defaults, bootstrap or eeprom. > > drivers/net/ethernet/broadcom/tg3.c > this driver seems to always force master mode > > drivers/net/phy/broadcom.c:39 > if ethernet controller is BCMA_CHIP_ID_BCM53573 and the PHY is PHY_ID_BCM54210E > then force master mode. > > drivers/net/phy/micrel.c:637 > Force master mode if devicetree property is set: micrel,force-master > > drivers/net/phy/realtek.c:173 > /* RTL8211C has an issue when operating in Gigabit slave mode * > return phy_set_bits(phydev, MII_CTRL1000, > CTL1000_ENABLE_MASTER | CTL1000_AS_MASTER)
Short of working around hardware issues, I wonder whether some of the above is due to not reading or understanding the 802.3 recommendation. However, it is just a recommendation, not a requirement.
-- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 10.2Mbps down 587kbps up
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