Subject: Re: uboot and ppc405

From: Jon Masters <[email-masked]>
Date: Tue, 26 Oct 2004 16:48:06 +0100

On Mon, 25 Oct 2004 22:39:30 -0700, Peter Ryser <[email-masked]> wrote:

jcm>> btw Peter, I've been moaning about the weird interrupt behaviour of
jcm>> the SysACE on e.g. the Memec board for some time (see archives for
jcm>> various other people's experiences too) - and I've spoken to several
jcm>> folks at Xilinx without getting very far. If there's a fundamental
jcm>> problem then it probably makes sense for us to help get it fixed.

> Hmm, I'm not aware of any interrupt problems with System ACE CF.

It issues an extra interrupt after each sector write on our hardware,
in what seems to be a reasonably reproducible but not entirely
predictable fashion. This is after the interrupt we expect to get on
sector completion - it causes the Monta driver to go belly up because
it has no handling to check for interrupt on QUEUE_EMPTY or similar
error conditions.

I have every confidence that it works on the ML300, just not on other
boards, including both the Memec board and our in house prototypes.
Since it's not a major issue right now to have good performance from
the SysACE (just a reliable driver), I've created the patch I posted
previously to use polled IO instead.

> There is now a MVL preview kit for the Memec board. You might want to
> try it out and see whether the problems you observe persist.

Is this the one which doesn't actually use the SystemACE for a filesystem?

> Looking at the postings back in April I can only say that I never saw
> any similar problems.

Others have done so. I'll check with the hardware guys and see if I
can't send you a simple hardware case that falls over at some point -
I'm slightly constrained to release hardware designs and so on until
after this thing is ready to ship.

> The implementation of System ACE CF functionality in U-Boot is written
> for polled operation. In that case Stephen Williams wrote the actual
> driver and we decided not to publish our own driver but reuse his.

So it probably doesn't use the Xilinx HAL, that can only be a good thing :-)

Jon.