if_msk.c link negotiation / packet drops

[YongHyeon PYUN]

On Tue, Oct 11, 2011 at 11:40:42AM -0400, Karim wrote:
> Hi List,
> 
> Using a Marvell NIC plugged into a CISCO switch I see the 
> auto-negotiation failing and even when forcing the device to full-duplex 
> we sometimes see packet drops.
> 
> Here is the device description from dmesg:
> 
> mskc0: <Marvell Yukon 88E8053 Gigabit Ethernet> port 0xbe00-0xbeff mem 
> 0xfdefc000-0xfdefffff irq 16 at device 0.0 on pci1
> msk0: <Marvell Technology Group Ltd. Yukon EC Id 0xb6 Rev 0x02> on mskc0
> msk0: Ethernet address: 00:03:2d:09:94:52
> miibus0: <MII bus> on msk0
> e1000phy0: <Marvell 88E1111 Gigabit PHY> PHY 0 on miibus0
> e1000phy0:  10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, 1000baseT, 
> 1000baseT-master, 1000baseT-FDX, 1000baseT-FDX-master, auto, auto-flow
> mskc0: [ITHREAD]
> 
> The switch its plugged in (Cisco) is configured for 100baseTX full-duplex.
> 
> ifconfig reports:
> 
> msk0: 
> flags=608843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST,SATELLITE,LAN_NET> 
> metric 0 mtu 1500
>         options=40018<VLAN_MTU,VLAN_HWTAGGING>

The flags and options show that you're using very customized
driver, right?

>         ether 00:03:2d:09:94:52
>         inet 192.168.122.7 netmask 0xffffff00 broadcast 192.168.122.255
>         media: Ethernet autoselect (100baseTX <half-duplex>)
	  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Resolved duplex is half so I guess it would be normal to see
dropped frames which may be triggered by collision.

>         status: active
> 
> I added a bit of debugging code in e1000phy_status in the hope to 
> understand what was going on:
> 
>     bmsr = PHY_READ(sc, E1000_SR) | PHY_READ(sc, E1000_SR);
>     bmcr = PHY_READ(sc, E1000_CR);
>     ssr = PHY_READ(sc, E1000_SSR);
> 
>     printf("%s ssr 0x%x bmsr 0x%x bmcr 0x%x\n", __func__, ssr, bmsr, bmcr);
> 
> Which consistently gives:
> 
>  kernel: e1000phy_status ssr 0x4d00 bmsr 0x796d bmcr 0x1000
> 

This register value is consistent with media status of ifconfig
output. The real question is why auto-negotiation does not work
against your switch. It could be a bug in switch side and if you
have to manually set full-duplex with msk(4), please make sure your
switch's duplex configuration also should be manually set to
full-duplex. Otherwise resolved duplex is half.

> Now and then the system will report the device is going inactive and we 
> can see packet drops when that happens. This repeat itself once in a 
> while without being predictable.
> 

Check MAC H/W statistics counter and see any
collisions(dev.msk.0.stats)

> By the way on a 7.4 system this was happening every 10 min. Using a 
> driver from FBSD9 back ported to 7.4 we see the issue at a much lower 
> frequency (every 30 min) but the issue is still there.
> 
> Cheers,
> 
> Karim.