Re: [openib-general] [PATCH v3 1/7] AMSO1100 Low Level Driver.

[Grant Grundler]

On Fri, Jun 23, 2006 at 04:04:31PM +0200, Arjan van de Ven wrote:
> > I thought the posted write WILL eventually get to adapter memory.  Not
> > stall forever cached in a bridge.  I'm wrong?
> 
> I'm not sure there is a theoretical upper bound.... 

I'm not aware of one either since MMIO writes can travel
across many other chips that are not constrained by
PCI ordering rules (I'm thinking of SGI Altix...)

> (and if it's several msec per bridge, then you have a lot of latency
> anyway)

That's what my original concern was when I saw you point this out.
But MMIO reads here would be expensive and many drivers tolerate
this latency in exchange for avoiding the MMIO read in the
performance path.

grant
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