From: James Bottomley <James.Bottomley@steeleye.com>
To: David Gibson <david@gibson.dropbear.id.au>,
James Bottomley <James.Bottomley@SteelEye.com>,
"Adam J. Richter" <adam@yggdrasil.com>,
linux-kernel@vger.kernel.org
Subject: Re: [RFC] generic device DMA implementation
Date: Thu, 05 Dec 2002 09:03:24 -0600 [thread overview]
Message-ID: <200212051503.gB5F3Q601998@localhost.localdomain> (raw)
In-Reply-To: Message from David Gibson <david@gibson.dropbear.id.au> of "Thu, 05 Dec 2002 16:05:36 +1100." <20021205050536.GE1500@zax.zax>
david@gibson.dropbear.id.au said:
> But if you have the sync points, you don't need a special allocater
> for the memory at all - any old RAM will do. So why not just use
> kmalloc() to get it.
Because with kmalloc, you have to be aware of platform implementations. Most
notably that cache flush/invalidate instructions only operate at the level of
certain block of memory (called the cache line width). If kmalloc returns
less than a cache line width you have the potential for severe cockups because
of the possibility of interfering cache operations on adjacent kmalloc regions
that share the same cache line.
the dma_alloc... function guarantees to avoid this for you by passing the
allocation to the platform layer which knows the cache characteristics and
requirements for the machine (and dma controller) you're using.
James
next prev parent reply other threads:[~2002-12-05 14:55 UTC|newest]
Thread overview: 119+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-12-04 17:47 [RFC] generic device DMA implementation James Bottomley
2002-12-04 18:27 ` Jeff Garzik
2002-12-04 19:36 ` James Bottomley
2002-12-04 21:19 ` Miles Bader
2002-12-04 21:21 ` Miles Bader
2002-12-04 21:42 ` James Bottomley
2002-12-05 5:44 ` Miles Bader
2002-12-04 21:46 ` James Bottomley
2002-12-05 2:31 ` Miles Bader
2002-12-05 3:06 ` James Bottomley
2002-12-05 5:02 ` David Gibson
2002-12-05 11:15 ` Benjamin Herrenschmidt
2002-12-05 11:16 ` William Lee Irwin III
2002-12-05 15:12 ` James Bottomley
2002-12-05 0:47 ` David Gibson
2002-12-05 0:54 ` Jeff Garzik
2002-12-05 1:44 ` James Bottomley
2002-12-05 2:38 ` David Gibson
2002-12-05 3:13 ` James Bottomley
2002-12-05 5:05 ` David Gibson
2002-12-05 15:03 ` James Bottomley [this message]
2002-12-05 23:54 ` David Gibson
2002-12-05 3:17 ` Miles Bader
2002-12-05 6:06 ` David Gibson
2002-12-05 6:43 ` Miles Bader
2002-12-05 23:44 ` David Gibson
2002-12-06 2:23 ` Miles Bader
2002-12-05 3:41 ` Jeff Garzik
2002-12-05 6:04 ` David Gibson
2002-12-05 16:29 ` Jeff Garzik
2002-12-05 23:59 ` David Gibson
2002-12-05 11:08 ` Benjamin Herrenschmidt
2002-12-05 11:35 ` Russell King
2002-12-05 15:24 ` James Bottomley
2002-12-06 0:01 ` David Gibson
-- strict thread matches above, loose matches on Subject: below --
2002-12-18 3:01 [RFT][PATCH] " James Bottomley
2002-12-18 3:13 ` David Mosberger
2002-12-28 18:14 ` Russell King
2002-12-28 18:19 ` James Bottomley
2002-12-07 14:37 [RFC] " Adam J. Richter
2002-12-07 4:12 Adam J. Richter
2002-12-06 22:52 Adam J. Richter
2002-12-06 22:17 Adam J. Richter
2002-12-06 22:26 ` James Bottomley
2002-12-06 22:29 ` David S. Miller
2002-12-06 22:48 ` James Bottomley
2002-12-06 22:49 ` David S. Miller
2002-12-06 22:32 ` Arjan van de Ven
2002-12-06 17:39 Adam J. Richter
2002-12-06 18:07 ` Matthew Wilcox
2002-12-06 17:07 Adam J. Richter
2002-12-06 16:48 James Bottomley
2002-12-06 16:19 Adam J. Richter
2002-12-06 16:40 ` Matthew Wilcox
2002-12-06 18:17 ` David S. Miller
2002-12-06 18:29 ` James Bottomley
2002-12-06 18:31 ` David S. Miller
2002-12-06 18:40 ` James Bottomley
2002-12-06 18:42 ` David S. Miller
2002-12-06 21:04 ` Oliver Xymoron
2002-12-07 10:19 ` David Gibson
2002-12-06 18:36 ` Matthew Wilcox
2002-12-06 18:38 ` David S. Miller
2002-12-06 7:41 Adam J. Richter
2002-12-06 15:50 ` David S. Miller
2002-12-06 7:14 Adam J. Richter
2002-12-06 16:26 ` James Bottomley
2002-12-06 17:48 ` Miles Bader
2002-12-07 9:56 ` David Gibson
2002-12-07 9:45 ` David Gibson
2002-12-07 11:26 ` Russell King
2002-12-08 5:28 ` David Gibson
2002-12-06 6:15 David Brownell
2002-12-06 2:08 Adam J. Richter
2002-12-06 2:53 ` David Gibson
2002-12-06 4:03 ` David S. Miller
2002-12-05 20:27 Adam J. Richter
2002-12-05 17:49 Manfred Spraul
2002-12-06 0:08 ` David Gibson
2002-12-05 12:21 Adam J. Richter
2002-12-05 12:44 ` Russell King
2002-12-05 12:13 Adam J. Richter
2002-12-05 11:57 Adam J. Richter
2002-12-06 0:06 ` David Gibson
2002-12-05 5:20 Adam J. Richter
2002-12-05 3:02 Adam J. Richter
2002-12-05 6:15 ` David Gibson
2002-12-05 1:21 Adam J. Richter
2002-12-05 2:40 ` David Gibson
2002-12-05 2:49 ` Miles Bader
2002-12-05 6:12 ` David Gibson
2002-12-05 0:43 Adam J. Richter
2002-12-05 0:55 ` Jeff Garzik
2002-12-05 2:02 ` James Bottomley
2002-11-09 4:51 [parisc-linux] Untested port of parisc_device to generic device interface Adam J. Richter
2002-11-09 5:21 ` Matthew Wilcox
2002-11-09 6:03 ` Greg KH
2002-11-09 15:33 ` J.E.J. Bottomley
2002-11-13 6:13 ` Greg KH
2002-11-13 7:46 ` Miles Bader
2002-11-13 7:52 ` Greg KH
2002-11-13 8:02 ` Miles Bader
2002-11-13 8:10 ` Greg KH
2002-11-13 8:26 ` Miles Bader
2002-11-13 8:25 ` Greg KH
2002-11-13 9:05 ` Miles Bader
[not found] ` <miles@lsi.nec.co.jp>
2002-11-13 20:13 ` Grant Grundler
2002-11-13 20:21 ` J.E.J. Bottomley
2002-11-13 20:37 ` Grant Grundler
2002-11-13 11:59 ` Ivan Kokshaysky
2002-11-13 12:36 ` Marc Zyngier
2002-11-13 16:32 ` Bjorn Helgaas
2002-11-13 17:23 ` J.E.J. Bottomley
2002-11-13 20:33 ` Grant Grundler
2002-11-13 20:44 ` J.E.J. Bottomley
2002-11-13 21:42 ` Grant Grundler
2002-11-13 20:12 ` Grant Grundler
2002-11-09 7:58 ` Marc Zyngier
2002-11-09 18:04 ` Grant Grundler
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