missing half-duplex support with L2-switch

bba — Fri, 23 Mar 2012 12:45:07 GMT

Hello,

we want to use the L2-switch on our own hardware and found that half-duplex connections are not supported. Comparing with the iMX28 EVK we got the same results.

The L2-switch will be configured inside the kernel config as follows.

Linux Kernel Configuration
-> Device Drivers
--> Network device support
---> Ethernet (10 or 100Mbit)
----> L2 Switch Ethernet Controller (of ColdFire CPUs)

and if we plupped in/off an network cable, we got following.

root@imx28evk ~$ PHY: 0:01 - Link is Up - 10/Half
PHY: 0:01 - Link is Up - 10/Half
PHY: 0:01 - Link is Up - 10/Half
PHY: 0:01 - Link is Up - 10/Half
PHY: 0:01 - Link is Up - 10/Half
PHY: 0:01 - Link is Up - 10/Half
PHY: 0:01 - Link is Up - 10/Half
PHY: 0:01 - Link is Down
PHY: 0:00 - Link is Up - 10/Half
PHY: 0:00 - Link is Up - 10/Half
PHY: 0:00 - Link is Up - 10/Half
PHY: 0:00 - Link is Up - 10/Half
PHY: 0:00 - Link is Up - 10/Half
PHY: 0:00 - Link is Down

Searching for the reason inside the kernel sourcecode, I've added some debug code into drivers/net/phy/phy.c. - void phy_state_machine(struct work_struct *work).

Here I've seen that the state handler for port 1 floated between 6 ond 9, PHY_RUNNING and PHY_CHANGELINK and sends the Link is Up - 10/Half message.

Searching further, I found the missing part inside static fec-switch.c - void switch_adjust_link0(struct net_device *dev)

    /* Duplex link change */
   if (phy_dev->link) {
       if (fep->full_duplex != phy_dev->duplex)
           status_change = 1;
   }

!!! Here all the time a status_change will be detected !!!

Comparing with fec.c - static void fec_enet_adjust_link(struct net_device *dev)

   /* Duplex link change */
   if (phy_dev->link) {
       if (fep->full_duplex != phy_dev->duplex) {
           fec_restart(dev, phy_dev->duplex);
           status_change = 1;
       }
   }

there is no function like fec_restart(dev, phy_dev->duplex) for the L2-switch.

Is there any solution available to use a half-duplex connection together with the L2-switch?

The 10/Half duplex link works fine using normal eth setting without l2-switch

Kind regards,

Birger

Re: missing half-duplex support with L2-switch

bba — Wed, 11 Apr 2012 15:12:24 GMT

Hello,

I have tried to insert the switch_restart function. Than the periodical "PHY: 0:01 - Link is Up - 10/Half" were removed, but no communication were posssible with 10MBit/Half-duplex, so the code inside switch_restart() seams to be wrong.

/* Duplex link change */

if (phy_dev->link) {

    if (fep->full_duplex != phy_dev->duplex) {
        switch_restart(dev, phy_dev->duplex);
        status_change = 1;
    }
}

We also found, that 100Mbit/Half-duplex seams to be working in one pc/networkcard/switch combination with the modification above.

Regards,

Birger

Re: missing half-duplex support with L2-switch

bba — Wed, 25 Apr 2012 09:00:10 GMT

Hello, there is a patch from Qiang Li.

http://imxcommunity.org/profiles/blogs/bug-fix-for-imx28-l2-switch-can-t-work-in-10base-t-network?xg_source=activity

Regards,

Birger

i.MX Processors中的主题 missing half-duplex support with L2-switch

missing half-duplex support with L2-switch

Re: missing half-duplex support with L2-switch

Re: missing half-duplex support with L2-switch