From: Matt Porter <mporter@kernel.crashing.org>
To: Conor McLoughlin <cml3227@eircom.net>
Cc: linuxppc-embedded <linuxppc-embedded@ozlabs.org>
Subject: Re: Does kmalloc on MPC82xx work correctly with GFP_DMA?
Date: Tue, 19 Oct 2004 07:27:54 -0700 [thread overview]
Message-ID: <20041019072754.A29957@home.com> (raw)
In-Reply-To: <41738D27.4060007@eircom.net>; from cml3227@eircom.net on Mon, Oct 18, 2004 at 10:30:15AM +0100
On Mon, Oct 18, 2004 at 10:30:15AM +0100, Conor McLoughlin wrote:
> I have been looking at the ethernet device driver (fcc_enet) for the
> mpc82xx platform. This allocates buffer descriptors using kmalloc with
> the GFP_DMA flag. As far as I can see on my platform, this allocates
GFP_DMA has no meaning on PPC. All memory is DMAable. GFP_DMA is for
PeeCees with a limited ISA DMA space. Drivers should be using GFP_KERNEL
so they don't confuse people.
> from the regular kernel memory (0xCxxxxxxx). As the attributes of this
> block of memory are controlled by the block address translation
> registers, this cannot be DMA safe, can it?
Sure it can. It works with hardware snooping.
> Is there something I am missing here?
Yes, it's a 603e core and hardware snooping support manages cache
coherency between system memory and devices.
-Matt
prev parent reply other threads:[~2004-10-19 14:56 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-10-18 4:01 SCC UART hang Jeff Angielski
2004-10-18 9:30 ` Does kmalloc on MPC82xx work correctly with GFP_DMA? Conor McLoughlin
2004-10-18 15:31 ` Dan Malek
2004-10-19 8:36 ` Conor McLoughlin
2004-10-19 14:15 ` Dan Malek
2004-10-19 15:26 ` Conor McLoughlin
2004-10-19 14:31 ` Matt Porter
2004-10-19 14:27 ` Matt Porter [this message]
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