At 04:21 PM 2/24/99 +0000, you wrote:
>Has anyone tried a PCNET AM79C971 based card on EBSA285 ?
>Mine doesn't works, it is detected by driver but sends nothing
>to the network
As Phil said the problem is probably due to cache consistency (or the lack
of it)
on the EBSA.
Intel, Alpha and SPARC PCI systems provide cache coherency between the PCI bus
and the processor - so if the Net card writes to main memory and then the host
looks at that location it will pretty much immediatly see the change.
On systems based around the StrongARM/21285 combination if the location
happened to be previously in the processor cache then even after the write
by the net card, the processor will see the old value. This confuses the hell
out of the network drivers which presume they are on a system like Intel.
The tulip driver has been suitably frobbed to perform cache invalidation
where needed;
but this is not true of other drivers.
One way to see if this is the problem is to disable the processor cache by
editing
head-armv.S - there is somewhere where it sets up the cache and write
buffers; with
a line something like (I dont have the source in front of me!):
orr r0,r0, #????? ; Set bits in MMU registers I*******DW*
(No I can't remember the details - but the thing to look for is this string
of letters
at the end with separators with a DW near one end). You want to add a bic
below it
to clear the DW bits to disable the data cache and writebuffer.
Dave
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