Re: PCI target implementation on AMCC PPC CPUs

[David Hawkins <dwh@ovro.caltech.edu>]

Hi Matthias,

> I must admit, that the AMCC PowerPC's PCI interrupt capabilities could
> be better:-) In both directions the host CPU has to do PCI
> configuration cycles either to generate or acknowledge an interrupt.
> The later is problematic for some OS coming from Redmond: you 
> have to do pci configuration cycles from interrupt level - and
> these OS do not 'like' that. 

Yikes. I'm sure there were some headaches there.

> In later designs and where possible we also switched to alternative
> interrupt mechanisms (GPIO for target to host and gated flags in FPGA
> registers for the other direction). Multiple interrupt sources 
> are identified by messages that are written to the other sides
> memory.
> 
> I think we should stop this discussion because its a little bit
> off-topic on this list.

I think this particular piece of info is important on
this list. It'll help those looking for processor options
that happen to search back through the list messages.

I'm done now, I just wanted to satisfy my curiosity
(and I did learn how the host can interrupt the core!).

I know that Leonid has hardware with these CPUs on them,
and he wanted some feedback on the AMCCs as target processor.
I'd eliminated the processor before getting it fully into
a design; so your experience is a little further on.

However, the conclusion remains the same; try to avoid
using the 440EP as a PCI target device.

Cheers,
Dave