Re: [PATCH -rt DO NOT APPLY] Fix for tg3 networking lockup

Michael Chan <mchan <at> broadcom.com> writes:

Turning off ASF is just a matter of changing some bits in NVRAM
and recalculating the checksum.  If you need the tool to do this,
I'll have someone send it to you.

Note that on some of the blade servers, I believe ASF is vital
and should not be disabled.

Still, it would be great if ASF could be disabled, because I have
noticed that when ASF is enabled, the tg3 driver automatically disables
TSO (TCP Segmentation Offloading). Here is a dmesg output from a server
where I am seeing that behavior:

  eth0: Tigon3 [partno(BCM95704A6) rev 2100 PHY(5704)] (PCIX:133MHz:64-bit) \
    10/100/1000BaseT Ethernet 00:30:48:59:c4:94
  eth0: RXcsums[1] LinkChgREG[0] MIirq[0] ASF[1] Split[0] WireSpeed[1] TSOcap[0]
  [...]
  eth1: Tigon3 [partno(BCM95704A6) rev 2100 PHY(5704)] (PCIX:133MHz:64-bit) \
    10/100/1000BaseT Ethernet 00:30:48:59:c4:95
  eth1: RXcsums[1] LinkChgREG[0] MIirq[0] ASF[0] Split[0] WireSpeed[1] TSOcap[1]

Both interfaces are fundamentally TSO-capable, but since ASF is enabled
on eth0, tg3 disables TSO on this interface. Of course at this point it
is not even possible to use ethtool to re-enable it because the driver
considers eth0 as not TSO-capable at all.

As far as I know, the tg3 driver has been doing that since one of your
patches shipped with 2.6.11-rc2-bk3, Michael, see [1]. Here is the relevant
code snippet (line numbers are for 2.6.16):

  10835   if (tp->tg3_flags2 & TG3_FLG2_HW_TSO) {
  10836           tp->tg3_flags2 |= TG3_FLG2_TSO_CAPABLE;
  10837   }
  10838   else if (GET_ASIC_REV(tp->pci_chip_rev_id) == ASIC_REV_5700 ||
  10839       GET_ASIC_REV(tp->pci_chip_rev_id) == ASIC_REV_5701 ||
  10840       tp->pci_chip_rev_id == CHIPREV_ID_5705_A0 ||
  10841       (tp->tg3_flags & TG3_FLAG_ENABLE_ASF) != 0) {
  10842           tp->tg3_flags2 &= ~TG3_FLG2_TSO_CAPABLE;
  10843   } else {
  10844           tp->tg3_flags2 |= TG3_FLG2_TSO_CAPABLE;
  10845   }

The culprit is line 10841. Why is that done ?

[1] ftp://ftp.us.kernel.org:/pub/linux/kernel/v2.6/snapshots/old/
    patch-2.6.11-rc2-bk3.log, patch-2.6.11-rc2-bk3.bz2

--
Marc Bevand