Re: [PATCH] fsldma: use PCI Read Multiple command

[David Hawkins]

> > > > Can you give me an example of non-PCI memory that would be
> > > > non-prefetchable that you'd like us to try? We can see if our
> > > > host CPUs have an area like that ... we just need to know
> > > > what device to look for first :)
> > > You can mark the pci inbound window on the 83xx as non-prefetchable 
> > > (assuming 83xx is host). On a x86 host I doubt there is any easy way 
> > > to get non-prefetchable memory.
> >
> > Yep, we were going to do that, but chose to use the
> > 1MB region already setup for the IMMRs since its already
> > marked as non-prefetchable. We were only doing reads, so
> > it wasn't going to hurt anything.
> >
> > I doubt that marking one of the other BAR regions
> > as non-prefetchable will give a different result.
> > However, we're more than happy to double-check if
> > you'd like.
>
> Its possible you'll get a different result since IMMR is a register 
> space internal and thats normally a completely different bus than memory 
> would be (internal to the 83xx).  I'd suggest double-checking w/a BAR 
> marked non-prefetch pointing to real memory.

We had a 4k BAR1 setup to point to DDR memory.

With prefetchable set, a 36-byte transfer generated a
burst-of-8 32-bit words followed by a single transaction.

With non-prefetchable set, the transfers were all single.

So it works like we'd expect.

Cheers,
Dave

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/