Disable cache on 74xx
Mark A. Greer
mgreer at mvista.com
Fri Feb 21 03:51:23 EST 2003
I know you are aware of this but I *always* experience cache coherency
problems with the GT64260A when Sysclk/Tclk are anything above 100MHz
and I believe that your board is clocked over that. Try a 100MHz
crystal and see if the problem goes away.
Dan Malek wrote:
> Brian Waite wrote:
> > .... The memory controller (gt64260) seems to be
>> doing something very wrong and it is thought to be a cache coherency
> The problem is cache coherency is central to the operation of processor
> bus. One possibility, especially in the example you described, is the gt
> is generating incorrect cache coherency control cycles on the bus.
> the processor cache isn't going to affect this.
>> So to prove this, I was asked to try running without any sort of cache.
> Make sure you disable it in the memory controller as well.
>> Hopefully between Gary's information and yours, Dan I can convince
>> that it is futile.
> Linux is a very poor diagnostic tool. When I run Linux and discover this
> type of problem, I reduce it down into a non-Linux diagnostic that can
> generate the same type of bus cycles. That way you can just flash it
> rom and let some hardware engineer run it over and over without having to
> boot up something as complex as Linux and sorting through millions of
> bus cycles for the failure mode. With these types of problems you have
> to determine exactly what causes the failure. Since the processor hangs
> so completely it should be easy to see the condition of the failure. If
> it is a memory controller timing problem, you should see exactly what
> failed and it should be clear how to program the controller to correct
> Of course, like Ben said, check the errata.
> Good Luck.
> -- Dan
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