Roland Dreier <[email protected]> writes:
> > Roland is the mlx4 sane enough to put the memory that needs
> > write-combining a prefetchable bar. So several cards can be combined
> > together?
>
> Yes, it is in a prefetchable BAR. It's the second half of the second
> BAR in:
>
> 0d:00.0 InfiniBand: Mellanox Technologies Unknown device 634a (rev a0)
> Subsystem: Mellanox Technologies Unknown device 634a
> Flags: bus master, fast devsel, latency 0, IRQ 16
> Memory at fc400000 (64-bit, non-prefetchable) [size=1M]
> Memory at d8000000 (64-bit, prefetchable) [size=8M]
> Memory at fc3fe000 (64-bit, non-prefetchable) [size=8K]
> Capabilities: <access denied>
>
> but I'm not sure what you mean about combining several cards?
So in general the pci prefetchable attribute means write-combining as
well as prefetching is safe. A sane BIOS will allocate prefetchable
BARS contiguously in the address space. So on a good day you
can just use one MTRR to map all of the prefetchable BARs as write-combining.
Eric
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