Natsemi ethernet 'cable magic' fix can cause problems

Natsemi ethernet 'cable magic' fix can cause problems

[Colin Paton]

Hi,

This information may be useful to anyone who uses the natsemi ethernet
driver.

I have discovered that the 'do_cable_magic()' call introduced into the
driver in kernels 2.4.20 and later can cause problems.

Some machines we have use the Natsemi DP83815 chip, which worked with no
problems using kernel 2.4.19. Following an upgrade to 2.4.25 a few of
the boxes stopped working - but most were still OK.

The problem was strange - about 30% packet loss was experienced during
pings. Moving the box to a different ethernet wall outlet (but still
using the same port on the switch) cured the problem. The problem
therefore appeared to be cable dependant.

It would appear that the call to 'do_cable_magic()' in
drivers/net/natsemi.c causes the problem to occur.

It looks as though this was added in to actually *fix* such problems...
but in our case it made things worse.

The cable problems were never experienced before, and everything seems
fine now that this call has been removed.

I'm not sure of the correct way to fix this problem, but I'm hoping that
this information might be useful to others who encounter something
similar.

Colin

Re: Natsemi ethernet 'cable magic' fix can cause problems

[Tim Hockin]

On Thu, May 13, 2004 at 11:35:03AM +0100, Colin Paton wrote:
> The problem was strange - about 30% packet loss was experienced during
> pings. Moving the box to a different ethernet wall outlet (but still
> using the same port on the switch) cured the problem. The problem
> therefore appeared to be cable dependant.
> 
> It would appear that the call to 'do_cable_magic()' in
> drivers/net/natsemi.c causes the problem to occur.
> 
> It looks as though this was added in to actually *fix* such problems...
> but in our case it made things worse.

I'm the responsible party on that one.  do_cable_magic() was a direct
result of a significant amount of work with National's engineers to
root-cause some major problems we had had.

If I recall, the problem we experienced was when the cable was "short"
(where short was < 30m, I think).  What can you tell me about your cabling
setup?

Willing to test?  Ping me back.

Re: Natsemi ethernet 'cable magic' fix can cause problems

[Marcelo Tosatti]

On Thu, May 13, 2004 at 10:03:58AM -0700, Tim Hockin wrote:
> On Thu, May 13, 2004 at 11:35:03AM +0100, Colin Paton wrote:
> > The problem was strange - about 30% packet loss was experienced during
> > pings. Moving the box to a different ethernet wall outlet (but still
> > using the same port on the switch) cured the problem. The problem
> > therefore appeared to be cable dependant.
> > 
> > It would appear that the call to 'do_cable_magic()' in
> > drivers/net/natsemi.c causes the problem to occur.
> > 
> > It looks as though this was added in to actually *fix* such problems...
> > but in our case it made things worse.
> 
> I'm the responsible party on that one.  do_cable_magic() was a direct
> result of a significant amount of work with National's engineers to
> root-cause some major problems we had had.
> 
> If I recall, the problem we experienced was when the cable was "short"
> (where short was < 30m, I think).  What can you tell me about your cabling
> setup?
> 
> Willing to test?  Ping me back.

Hi Tim, Collin,

Did you made any progress on this issue?

Re: Natsemi ethernet 'cable magic' fix can cause problems

[Tim Hockin]

On Sat, Jul 31, 2004 at 11:51:13AM -0300, Marcelo Tosatti wrote:
> > If I recall, the problem we experienced was when the cable was "short"
> > (where short was < 30m, I think).  What can you tell me about your cabling
> > setup?
> > 
> > Willing to test?  Ping me back.
> 
> Hi Tim, Collin,
> 
> Did you made any progress on this issue?

Never gor any reply from him.