Module Name:	src
Committed By:	jonathan
Date:		Thu Nov 24 03:27:59 UTC 2005

Modified Files:
	src/sys/dev/pci: if_bge.c if_bgereg.h

Log Message:
Add TSO support to bge(4) for PCI-Express bge devices, which are
shipped from the factory with TSO-capable firmware.  The TSO support
here may also work on 5705 chips, but that is (so far) untested.

TSO support written after careful reading of the Linux tg3 driver,
and (after attempting to deconstruct the cut-and-paste mess therein)
very close reading of the Broadcom-supplied Linux driver, particularly
the building of Tx-DMA buffer descriptors (bds). The TSO code herein was
then rewritten from scratch, circa 4am local time, October 27 2005.
(In other words: this is 4am software; caveat emptor.)

Other magic register settings in this patch are required; without
them, attepmting to use TSO locks up the chip. The required register
settings were extracted from the cited Linux drivers.

Note that TSO-capable firmware for the 5703/5704 is distributed in
non-GPL form with the aforementioned Linux drivers. Once the 5705 case
is debugged, (particularly the pseudo-header checksum precalculation
flagged with an XXX) downloading that TSO-capable firmware to the
5703/5704 should, in principle, enable TSO support on all but the
original bcm5700 (I forget if the 5701 can support TSO, or not).

Note also that the ``hard case '' of IP/TCP headers spanning more than
one mbuf is not handled; I haven't been able to trigger it.  In any
case, since TSO applies only to packets generated by the local TCP,
and our TCP always leaves space for TCP headers and a normal IP
header, TSO on an IP/TCP header spanning multiple headers can only
arise due to insertion of IP options. I beleive that we are clearly
better off outlawing that case, and requiring ip_insertoptions()
to  pull-up TCP headers on any packets with M_CSUM_TSOv4 set.

As far as I know, bge hardwar does not support TSO for IPv6.


To generate a diff of this commit:
cvs rdiff -r1.94 -r1.95 src/sys/dev/pci/if_bge.c
cvs rdiff -r1.27 -r1.28 src/sys/dev/pci/if_bgereg.h

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.