Mark S. Mathews wrote:

Howdy Folks,

We've been working with the embedded 2.2.13 kernel on an RPX-Lite CW with
a XPC823ZT66A processor running at the 50MHz/8MHz setting.

It's not only the RPX Lite.....I have a variety of 8xx boards
and when I have trouble like this with a particular card, it
occurs in all of the boards.

............ but our
accesses to the common memory regions of the card are twitchy.

Same thing I have seen.  The I/O and attribute regions seem
to work OK, but memory regions don't.....on more than one
type of card.

.....but eventually we wind up with a machine-check.

Which points to some kind of bus timing or protocol problem.

runs well on the x86, our PowerBook, and on a different 860 based platform
(non-Linux, no MMU) so we're fairly confident it isn't the code.

Well now, that's interesting (the no MMU, not the non-Linux
part :-).  With the MMU disabled, the accesses behave as guarded.
This is something I have not properly implemented on the 8xx,
and with my somewhat sloppy use of eieio() and synchronization,
I am always waiting for this to come back and haunt me.  Notice
how I buried this important fact in this paragraph.  I will now
properly implement this (yet tonight).  Tell me the kernel version
you are using and I will send some updates for your testing.


How does someone (like me :-) determine what a PCMCIA interface
in something like a PowerBook uses for bus timing?

One specific question...when setting up the PCMCIA bus timings, the 823
book lists the settings in units of "clock cycles".  Which clock?

It is the CLKOUT (system/bus) clock.  On the 66MHz processor,
this better be 33 MHz (processor clock / 2).  For 50 MHz or
less, the CLKOUT is the processor clock.


	-- Dan

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