kern/128833: [bge] Network packets corrupted when bge card is in 64-bit PCI slot

[David Christensen]

The following reply was made to PR kern/128833; it has been noted by GNATS.

From: "David Christensen" <davidch at broadcom.com>
To: "Marius Strobl" <marius at alchemy.franken.de>
Cc: "bug-followup at FreeBSD.org" <bug-followup at FreeBSD.org>
Subject: RE: kern/128833: [bge] Network packets corrupted when bge card
 is in 64-bit PCI slot
Date: Mon, 24 Nov 2008 11:28:10 -0800

 > > There is a documented errata for the 5701 A3 where a 64bit DMA
 > > read can be terminated early by the bridge and then completed
 > > later as a 32bit access, causing corruption on the 5701. The
 > > errata states this type of behavior is rare in bridges and that
 > > the workaround is to force 32bit operation (set bit 15 of register
 > > 0x6800).  It's not clear whether this errata is occurring without
 > > seeing a but trace but it certainly sounds right.  The only
 > > question would be knowing "when" to force 32bit operation.  Should
 > > it be done in all cases or only for this bridge?
 > >
 >=20
 > David,
 >=20
 > could it be that bug doesn't only affect 5701 A3 but also
 > B3 (i.e. chipid 0x01050000) as in this case or even all 5701
 > revisions?=20
 
 I checked the assembly instructions for the 5701 and even though
 the ASIC ID decodes as B5, the revision of the chip is actually
 A3.  (You should be able to verify this as the silkscreen on the
 part should show "P13".)  Unfortunately the "friendly" revision
 of the chip doesn't match the "ASIC" revision of the chip for the
 5701 and the errata references the "friendly" name.  The result
 is that the part you know as B5 is affected by this errata.  Other
 versions of the chip (A2 which you know as B2 and A1 which you=20
 know as B1) are not subject to this errata.
 
 > How does the problem you describe relate to the
 > 5701 PCI-X issue, which we align the RX buffer differently
 > for as a workaround, would that problem also be avoided
 > by limiting 5701 to 32-bit operations? Or is the A3-errata
 > you described an entirely different issue and limited to 5701
 > in a 64-bit non-PCI-X slot, or would 5701 in a PCI-X slot
 > even require both workarounds?
 
 Which PCI-X issue are you referring to?  Can you point me to
 the line number on http://fxr.watson.org/fxr/source/dev/bge/if_bge.c?
 
 Dave