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Re: [PATCH] use mmiowb in tg3.c

To: "David S. Miller" <davem@xxxxxxxxxxxxx>
Subject: Re: [PATCH] use mmiowb in tg3.c
From: Jesse Barnes <jbarnes@xxxxxxx>
Date: Thu, 21 Oct 2004 22:01:34 -0500
Cc: Jesse Barnes <jbarnes@xxxxxxxxxxxx>, akpm@xxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, netdev@xxxxxxxxxxx, jgarzik@xxxxxxxxx, gnb@xxxxxxx, akepner@xxxxxxx
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References: <200410211613.19601.jbarnes@xxxxxxxxxxxx> <200410211628.06906.jbarnes@xxxxxxxxxxxx> <20041021164007.4933b10b.davem@xxxxxxxxxxxxx>
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On Thursday, October 21, 2004 6:40 pm, David S. Miller wrote:
> On Thu, 21 Oct 2004 16:28:06 -0700
>
> Jesse Barnes <jbarnes@xxxxxxxxxxxx> wrote:
> > This patch originally from Greg Banks.  Some parts of the tg3 driver
> > depend on PIO writes arriving in order.  This patch ensures that in two
> > key places using the new mmiowb macro.  This not only prevents bugs (the
> > queues can be corrupted), but is much faster than ensuring ordering using
> > PIO reads (which involve a few round trips to the target bus on some
> > platforms).
>
> Do other PCI systems which post PIO writes also potentially reorder
> them just like this SGI system does?  Just trying to get this situation
> straight in my head.

The HP guys claim that theirs don't, but PPC does, afaik.  And clearly any 
large system that posts PCI writes has the *potential* of reordering them.

Thanks,
Jesse

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