From: Dave Olien <firstname.lastname@example.org> To: email@example.com Cc: "David S. Miller" <firstname.lastname@example.org>, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com Subject: Re: DAC960 in 2.5.38, with new changes Date: Tue, 24 Sep 2002 10:28:43 -0700 [thread overview] Message-ID: <20020924102843.C17658@acpi.pdx.osdl.net> (raw) In-Reply-To: <firstname.lastname@example.org>; from email@example.com on Tue, Sep 24, 2002 at 10:11:26AM -0700 Hmm, interesting. A big part of what I'm doing to the driver right now is plugging in calls to the PCI DMA interfaces. So unless the underlying implementation is aware of these platform limitations and "doing the right thing", I'm adding a bunch of bounce buffer activity for many ia64 platforms. That would be too bad. I distantly recall that the cost of doing PCI DAC isn't really that high for bursty transfers, because the bus is able to group packets of data cycles behind one initial address cycle. But it's been many years since I last looked at this and I could have this wrong. On Tue, Sep 24, 2002 at 10:11:26AM -0700, David Mosberger wrote: > >>>>> On Tue, 24 Sep 2002 09:54:56 -0700, Dave Olien <firstname.lastname@example.org> said: > > Dave> According to the Documentation/DMA-mapping.txt file, the new > Dave> DMA mapping interfaces should allow all PCI transfers to use > Dave> 32-bit DMA addresses. Controllers on the PCI bus should never > Dave> need to use DAC PCI transfers. Based on this, writel() should > Dave> work even on ia64. > > Warning: there is a big difference between *can* and *want*. On ia64 > machines with an Intel chipset, the PCI DMA interface is implemented > via bounce buffers, so it will be *much* slower than DAC. For this > reason, it is preferable on ia64 to use DAC where possible (and just > in case Dave Miller starts asking about this: yes, the hp zx1 chipset > for Itanium 2 does have a hardware I/O TLB... ;-). > > --david
next prev parent reply other threads:[~2002-09-24 17:41 UTC|newest] Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top 2002-09-23 19:04 Dave Olien 2002-09-23 19:19 ` David Mosberger 2002-09-23 20:40 ` David S. Miller 2002-09-23 20:53 ` David Mosberger 2002-09-23 20:57 ` David S. Miller 2002-09-23 21:24 ` David Mosberger 2002-09-23 21:17 ` David S. Miller 2002-09-23 21:32 ` David Mosberger 2002-09-23 21:28 ` David S. Miller 2002-09-23 21:31 ` Daniel Phillips 2002-09-23 21:33 ` David Mosberger 2002-09-23 21:28 ` David S. Miller 2002-09-23 21:40 ` Daniel Phillips 2002-09-23 21:45 ` David Mosberger 2002-09-23 20:44 ` Daniel Phillips 2002-09-23 20:54 ` David S. Miller 2002-09-24 16:54 ` Dave Olien 2002-09-24 17:11 ` David Mosberger 2002-09-24 17:28 ` Dave Olien [this message] 2002-09-24 18:21 ` David Mosberger 2002-09-24 18:25 ` Dave Olien 2002-09-24 19:12 ` David Mosberger 2002-09-24 18:45 ` Dave Olien 2002-09-24 17:50 ` Daniel Phillips 2002-09-24 18:27 ` David Mosberger 2002-09-24 17:39 ` Daniel Phillips 2002-09-25 22:20 ` DAC960, documentation links Daniel Phillips 2002-09-25 22:23 ` Daniel Phillips 2002-09-26 0:02 ` Mr. James W. Laferriere 2002-09-26 16:13 ` DAC960 in 2.5.38, with new changes Alan Cox 2002-09-24 17:45 ` Daniel Phillips 2002-09-25 21:42 ` davide.rossetti 2002-09-23 20:39 ` Daniel Phillips 2002-09-23 21:41 ` Dave Olien 2002-09-23 21:53 ` Daniel Phillips 2002-09-23 22:03 ` Dave Olien 2002-09-23 22:22 ` Daniel Phillips
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