On 05.04.2019 23:54, Florian Fainelli wrote: > On 4/5/19 2:52 PM, Heiner Kallweit wrote: >> On 05.04.2019 23:38, Heiner Kallweit wrote: >>> On 05.04.2019 23:27, Andrew Lunn wrote: >>>>> + if (linkmode_test_bit(ETHTOOL_LINK_MODE_1000baseT_Half_BIT, >>>>> + phydev->supported)) >>>>> + phydev->is_gigabit_capable = 1; >>>>> + if (linkmode_test_bit(ETHTOOL_LINK_MODE_1000baseT_Full_BIT, >>>>> + phydev->supported)) >>>>> + phydev->is_gigabit_capable = 1; >>>>> + >>>> >>>> What i'm trying to get at is, why do we need this bit of the patch? >>>> Why do we need this flag? The hardware should tell us if it can do >>>> gigabit. >>>> >>> The code to query BMSR_ESTATEN and MII_ESTATUS is in genphy_read_status. >>> However we also have to cover the case that this function isn't used. >>> Therefore I query phydev->supported before the speed could be limited. >>> (relying on the PHY driver not lying about gigabit capability) >>> This part of the patch is directly before of_set_phy_supported(). >>> >>> I just see that we can re-use is_gigabit_capable also in >>> genphy_config_advert. >>> >>> Of course I can read in every place the hardware for gigabit support. >>> But IMO this creates unnecessary code duplication. >>> >> I just see that we can reuse is_gigabit_capable also in >> genphy_config_advert(). >> >> And when checking occurrences of BMSR_ESTATEN there seems to be more >> work waiting: In swphy BMSR_ESTATEN is set, but MII_ESTATUS isn't >> configured. It just works by chance becausing reading this register >> returns the default 0xffff. > > It is not clear to me what we are trying to optimize for here, given > everything is pretty much a slow path anyway. I am concerned though > about mis-behaving PHYs where caching of BMSR_ESTATEN could result in > incorrect behaviors, I don't have any data to back that claim, but > reading the registers should always be the safest way to determine what > HW is capable of (famous last words). Not feeling strongly about either > direction though... >
At this point I have to quote Einstein: "If you can't explain it simply, you don't understand it well enough." Means I'll spend few more thoughts on it ..
