[PATCH 03/12] fs_enet: Add FEC TX Alignment workaround for MPC5121.

[John Rigby]

I was having deja-vu with this and realized that I have fixed at least some
of the objections to this patch.

Wolfgang you may want to look at the patch in my 5121 git tree here:

http://git.denx.de/?p=linux-mpc512x.git;a=commit;h=2950be3be42af7449941c3340998c27ef918f10f

It does runtime tx packet alignment  It also has fewer ifdefs and trys to
share more code.  It also has a header that explains everything including
that fact that there is not a runtime conflict sine the only other ppc that
has fec is 8xx which is not in the same family.

On Wed, May 6, 2009 at 4:42 PM, Grant Likely <grant.likely at secretlab.ca>wrote:

> On Wed, May 6, 2009 at 4:12 PM, Wolfgang Denk <wd at denx.de> wrote:
> > Dear Grant Likely,
> >
> > In message <fa686aa40905061337w6aa82f5aj787618ba108e528f at mail.gmail.com>
> you wrote:
> >>
> >> > The FEC on 5121 has problems with misaligned tx buffers.
> >> > The RM says any alignment is ok but empirical results
> >> > show that packet buffers ending in 0x1E will sometimes
> >> > hang the FEC. Other bad alignment does not hang but will
> >> > cause silent TX failures resulting in about a 1% packet
> >> > loss as tested by ping -f from a remote host.
> >> >
> >> > This patch is a work around that copies every tx packet
> >> > to an aligned skb before sending.
> >>
> >> OUCH!
> >
> > Yes :-(
> >
> >> > +#else
> >> > +#define tx_skb_align_workaround(dev, skb) (skb)
> >> > +#endif
> >>
> >> Another use of #ifdef blocks.  What is the multiplatform impact?
> >
> > Hm... Can you recommend a better way to solve the problem? Suggestions
> > are welcome.
>
> I'd rather see a runtime selectable workaround.  ie. enable it based
> on the compatible property.
>
> g.
>
> --
> Grant Likely, B.Sc., P.Eng.
> Secret Lab Technologies Ltd.
>
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