Network Driver and instruction cache.

[Joel Sherrill]

Brett Swimley wrote:
> 
> Hi all -

Well if no one else will reply...
 
> I'm porting the Motorola MCF5272 Coldfire to RTEMS and have run into an
> issue with the network driver while enabling the instruction cache on the
> ColdFire.

This type of issue is normally restricted to data caches.

Is this a network driver for the on-CPU NIC?  

Does the MCF5272 have some data caching tied to enabling the instruction 
caching?

> I'm running the latest snapshot of RTEMS 4.5.0.

I suspect you could be running any version and see the same behavior. :)

> When the instruction cache is disabled, and I try pinging my board, I get no
> errors and no packet loss. The network driver appears to work flawlessly.
> 
> I have tried several options for enabling my instruction cache.  Each option
> gives me less than perfect response from the network driver (either no
> response or lost packets) - but the rest of my application seems to be
> running perfectly.
> 
> Should I expect occasional packet losses from ping? 

Heavy flood pinging can result in lost packets.  Simple pinging on a
dedicated network should almost never result in one.

> If not, would anyone
> have any suppositions why enabling the instruction cache would impede the
> network driver/network stack?

My guess is that enabling the instruction cache makes all of the code
run faster thus exposing some window in your network driver.  It is
possible
that there is a window somewhere else if there are other devices
interacting. 

> I have tried disabling the cache on my memory mapped internal peripherals,
> which includes the on board Fast Ethenet controller.

This sounds like a data caching issue which doesn't sound like a
problem.

> Any suggestions would be appreciated.

I can bet you you would.  This could be hard to debug.

> Regards,
> 
> Brett Swimley
> Sr. Design Engineer
> Advanced Electronic Designs, Inc.
> brett.swimley at aedinc.net
> ph: 406-585-8892
> fax: 406-585-8893
> www.aedinc.net

-- 
Joel Sherrill, Ph.D.             Director of Research & Development
joel at OARcorp.com                 On-Line Applications Research
Ask me about RTEMS: a free RTOS  Huntsville AL 35805
Support Available                (256) 722-9985