On Sun, Feb 24, 2019 at 04:39:30PM +0100, Heiner Kallweit wrote: > On 24.02.2019 16:34, Russell King - ARM Linux admin wrote: > > On Sun, Feb 24, 2019 at 04:28:32PM +0100, Heiner Kallweit wrote: > >> On 24.02.2019 16:15, Russell King - ARM Linux admin wrote: > >>> On Sun, Feb 24, 2019 at 04:04:03PM +0100, Andrew Lunn wrote: > >>>>> I think what's not correct is that phydev->autoneg is set > >>>>> (by phy_device_create) for a fixed link. > >>>> > >>>> Fixed-link tries to emulate auto-neg: > >>>> > >>>> bmsr |= BMSR_LSTATUS | BMSR_ANEGCOMPLETE; > >>>> > >>>> Maybe it needs better emulation of auto-neg? > >>> > >>> Or maybe it needs to represent a fixed-speed PHY by clearing bit 1.3 > >>> (BMSR_ANEGCAPABLE). In any case, 0.12 (BMCR_ANENABLE) is not set, > >>> so according to 802.3-2015, we should not be setting 1.5 > >>> (BMSR_ANEGCOMPLETE). > >>> > >>> However, swphy does try to emulate autonegotiation - we do have cases > >>> where swphy is used in situations where the speed and duplex are not > >>> fixed. It returns an emulated link partner advertisement for the > >>> current speed, which would suggest that we should set BMCR_ANENABLE. > >>> > >> If we emulate auto-neg, then it's not needed to set the speed bits > >> in BMCR. Also what just comes to my mind, certain speeds like 1000BaseT > >> don't support forced mode. So we may have to go with auto-neg. > > > > Sure. > > > >> To avoid the original issue it should be sufficient to copy > >> supported -> advertising at a suited place. > > > Sorry, seems this wasn't clear enough. I don't mean to change > swphy but the user side. > > > Why bother - the software PHY emulation is an emulation to allow > > existing userspace that pre-dates the ethtool API to get some link > > parameters. If we augment the PHY emulation in non-standard ways, > > userspace will need to be updated to handle those non-standard > > ways. If userspace needs to be updated, why not just bite the > > bullet and update to ethtool APIs rather than adding more > > complication through an emulation layer? > > > It's not only userspace. Based on my limited knowledge of DSA this > code also uses e.g. genphy_read_status() with a fixed link.
DSA has support for phylink, which is perfectly capable of supporting fixed links without using fixed-phy.c, although we have no way to create that without DT. Support could be added for non-DT though. That would avoid using phylib functions to read back from a fixed-link PHY. Since phylink presents to the MAC a fixed link in the same abstract manner as a real PHY, it should result in a more elegant implementation. DSA already has phylink support to support SFPs. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up
