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From: "David S. Miller" <davem@davemloft.net>
To: raghavendra.koushik@neterion.com
Cc: akepner@sgi.com, jgarzik@pobox.com, netdev@oss.sgi.com,
	netdev@vger.kernel.org, ravinandan.arakali@neterion.com,
	leonid.grossman@neterion.com, rapuru.sriram@neterion.com
Subject: Re: [PATCH 2.6.12.1 5/12] S2io: Performance improvements
Date: Thu, 07 Jul 2005 20:00:34 -0700 (PDT)	[thread overview]
Message-ID: <20050707.200034.74747399.davem@davemloft.net> (raw)
In-Reply-To: <200507080106.j6816NKP022996@guinness.s2io.com>

From: "Raghavendra Koushik" <raghavendra.koushik@neterion.com>
Date: Thu, 7 Jul 2005 18:06:19 -0700

> wmb() is to ensure ordered PIO writes.

wmb() does no such thing.  It only has influence on
load and store instructions done by the local processor,
it has no effect on what the PCI bus may do with PIO
writes (ie. post them).

If you need a PIO to complete in a specific order, you
have to read it back.  If you need PIO operations to occur
in a specific order wrt. cpu memory operations, mmiowb()
is what you need to use.

  reply	other threads:[~2005-07-08  3:00 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2005-07-07 22:27 [PATCH 2.6.12.1 5/12] S2io: Performance improvements raghavendra.koushik
2005-07-07 23:15 ` Arthur Kepner
2005-07-08  1:06   ` Raghavendra Koushik
2005-07-08  3:00     ` David S. Miller [this message]
2005-07-08  3:08       ` Jeff Garzik
2005-07-08 15:31     ` Arthur Kepner
2005-07-08 18:16       ` Raghavendra Koushik
2005-07-08 18:17       ` Ravinandan Arakali
2005-07-12 20:27 ` Christoph Hellwig
2005-07-12 20:34   ` David S. Miller
2005-07-12 21:00     ` Ravinandan Arakali
2005-07-12 21:04       ` David S. Miller
2005-07-12 21:07         ` Christoph Hellwig
2005-07-12 21:26           ` Andi Kleen
2005-07-12 21:54         ` Ravinandan Arakali
2005-07-29 16:37         ` Ravinandan Arakali
2005-07-31 14:05           ` Christoph Hellwig
2005-08-02 23:13             ` Ravinandan Arakali
2005-08-02 23:26               ` 'Christoph Hellwig'
2005-07-12 20:56   ` Leonid Grossman
  -- strict thread matches above, loose matches on Subject: below --
2005-08-03 12:48 Prarit Bhargava

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