Hi, An upgrade from 2.6.34 to 2.6.35 caused networking to stop working on my MPC8313-based board. It turned out that TCP checksums were invalid, so I dug through the .35 changelog to try and isolate the reason. The change "tcp: Set CHECKSUM_UNNECESSARY in tcp_init_nondata_skb" seems to be the specific one that causes breakage - if I revert this one-liner, things work again:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=2e8e18ef52e7dd1af0a3bd1f7d990a1d0b249586 However, I also noticed that one of my boards was broken while a newer prototype (which is very similar, hardware-wise) was not. It turns out they're using 2 different revisions of silicon, so the broken board still has a 1.0 version microcontroller. Therefore I'm guessing (just a hunch) that the root cause of the problem is MPC8313 errata eTSEC12: ======== eTSEC12: Tx IP and TCP/UDP Checksum Generation not supported for some Tx FCB offsets Description: If the Tx FCB (Frame Control Block) 32-byte offset is 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E or 0x1F, IP and TCP/UDP header checksum generation do not function properly. The checksum value may be inserted in the wrong location or not inserted at all. IP and TCP/UDP header checksum generation is not supported in LINUX and other systems in which headers are prepended to pre-aligned packet data, or where the alignment of the Tx FCB cannot be controlled. This behavior applies to pseudo-header checksum insertion as well as checksum generation. Workaround: Align Tx FCB to a 16 or 32-byte boundary. If the alignment of TxFCB is not controllable, set TCTRL[TUCSEN]=0 and TCTRL[IPCSEN]=0 to disable IP and TCP/UDP header checksum generation. Fix plan: Fixed in Rev 2.0 ======== This appears to have been working previously, but doesn't work any more. I'm not familiar enough with Dave's checksum/sk_buff changes to figure out whether this errata is to blame, though, or how I should fix it if it is. Presumably there's some alignment magic needed in the sk_buff or gfar_add_fcb() to make sure that the microcontroller is happy with the FCB offset? Any tip on how I can solve this, or at least verify that this errata is at fault? Thanks in advance -- Matthew L. Creech _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
