On 11/14/2016 11:00 AM, Måns Rullgård wrote: > Florian Fainelli <f.faine...@gmail.com> writes: > >> On 11/14/2016 10:20 AM, Florian Fainelli wrote: >>> On 11/14/2016 09:59 AM, Sebastian Frias wrote: >>>> On 11/14/2016 06:32 PM, Florian Fainelli wrote: >>>>> On 11/14/2016 07:33 AM, Mason wrote: >>>>>> On 14/11/2016 15:58, Mason wrote: >>>>>> >>>>>>> nb8800 26000.ethernet eth0: Link is Up - 100Mbps/Full - flow control >>>>>>> rx/tx >>>>>>> vs >>>>>>> nb8800 26000.ethernet eth0: Link is Up - 100Mbps/Full - flow control off >>>>>>> >>>>>>> I'm not sure whether "flow control" is relevant... >>>>>> >>>>>> Based on phy_print_status() >>>>>> phydev->pause ? "rx/tx" : "off" >>>>>> I added the following patch. >>>>>> >>>>>> diff --git a/drivers/net/ethernet/aurora/nb8800.c >>>>>> b/drivers/net/ethernet/aurora/nb8800.c >>>>>> index defc22a15f67..4e758c1cfa4e 100644 >>>>>> --- a/drivers/net/ethernet/aurora/nb8800.c >>>>>> +++ b/drivers/net/ethernet/aurora/nb8800.c >>>>>> @@ -667,6 +667,8 @@ static void nb8800_link_reconfigure(struct >>>>>> net_device *dev) >>>>>> struct phy_device *phydev = priv->phydev; >>>>>> int change = 0; >>>>>> >>>>>> + printk("%s from %pf\n", __func__, __builtin_return_address(0)); >>>>>> + >>>>>> if (phydev->link) { >>>>>> if (phydev->speed != priv->speed) { >>>>>> priv->speed = phydev->speed; >>>>>> @@ -1274,9 +1276,9 @@ static int nb8800_hw_init(struct net_device *dev) >>>>>> nb8800_writeb(priv, NB8800_PQ2, val & 0xff); >>>>>> >>>>>> /* Auto-negotiate by default */ >>>>>> - priv->pause_aneg = true; >>>>>> - priv->pause_rx = true; >>>>>> - priv->pause_tx = true; >>>>>> + priv->pause_aneg = false; >>>>>> + priv->pause_rx = false; >>>>>> + priv->pause_tx = false; >>>>>> >>>>>> nb8800_mc_init(dev, 0); >>>>>> >>>>>> > > [...] > >>>>> And the time difference is clearly accounted for auto-negotiation time >>>>> here, as you can see it takes about 3 seconds for Gigabit Ethernet to >>>>> auto-negotiate and that seems completely acceptable and normal to me >>>>> since it is a more involved process than lower speeds. >>>>> >>>>>> >>>>>> >>>>>> OK, so now it works (by accident?) even on 100 Mbps switch, but it still >>>>>> prints "flow control rx/tx"... >>>>> >>>>> Because your link partner advertises flow control, and that's what >>>>> phydev->pause and phydev->asym_pause report (I know it's confusing, but >>>>> that's what it is at the moment). >>>> >>>> Thanks. >>>> Could you confirm that Mason's patch is correct and/or that it does not >>>> has negative side-effects? >>> >>> The patch is not correct nor incorrect per-se, it changes the default >>> policy of having pause frames advertised by default to not having them >>> advertised by default. > > I was advised to advertise flow control by default back when I was > working on the driver, and I think it makes sense to do so. > >>> This influences both your Ethernet MAC and the link partner in that >>> the result is either flow control is enabled (before) or it is not >>> (with the patch). There must be something amiss if you see packet >>> loss or some kind of problem like that with an early exchange such as >>> DHCP. Flow control tend to kick in under higher packet rates (at >>> least, that's what you expect). >>> >>>> >>>> Right now we know that Mason's patch makes this work, but we do not >>>> understand why nor its implications. >>> >>> You need to understand why, right now, the way this problem is >>> presented, you came up with a workaround, not with the root cause or the >>> solution. What does your link partner (switch?) reports, that is, what >>> is the ethtool output when you have a link up from your nb8800 adapter? >> >> Actually, nb8800_pause_config() seems to be doing a complete MAC/DMA >> reconfiguration when pause frames get auto-negotiated while the link is >> UP, > > This is due to a silly hardware limitation. The register containing the > flow control bits can't be written while rx is enabled.
You do a DMA stop, but you don't disable the MAC receiver unlike what nb8800_stop() does, why is not calling nb8800_mac_rx() necessary here? > >> and it does not differentiate being called from >> ethtool::set_pauseparam or the PHYLIB adjust_link callback (which it >> probably should), > > Differentiate how? Differentiate in that when you are called from adjust_link, why bother checking with netif_running() since you are only configuring the pause settings when phydev->link is set. Not that this matters much, but that's something the caller can tell you. > >> wondering if there is a not a remote chance you can get the reply to >> arrive right when you just got signaled a link UP? > > If you're attempting to send or receive things before you get the link > up notification, you shouldn't expect anything to work reliably. No kidding. -- Florian