From: Christoph Lameter <cl@linux-foundation.org>
To: Nicolas Pitre <nico@cam.org>
Cc: lkml <linux-kernel@vger.kernel.org>,
Russell King - ARM Linux <linux@arm.linux.org.uk>
Subject: Re: wrong usage of MAX_DMA_ADDRESS in bootmem.h
Date: Tue, 30 Sep 2008 14:56:26 -0500 [thread overview]
Message-ID: <48E2846A.4030802@linux-foundation.org> (raw)
In-Reply-To: <alpine.LFD.2.00.0809301513260.3635@xanadu.home>
Nicolas Pitre wrote:
> I have implemented highmem for ARM. To catch wrong usage of __pa() and
>
> One issue is that bootmem.h uses __pa(MAX_DMA_ADDRESS). However
> MAX_DMA_ADDRESS on ARM is defined as 0xffffffff because there is usually
> no restriction on the maximum DMA-able address.
>
> RMK suggested that those places should be using ISA_DMA_THRESHOLD
> instead -- here's an excert of our conversation on this topic:
>
ok so do
#define MAX_DMA_ADDRESS ISA_DMA_THRESHOLD
>> I suspect all those places which are doing __pa(MAX_DMA_ADDRESS) really
>> want to be using ISA_DMA_THRESHOLD - that's something to raise on LKML
>> if it's causing problems.
MAX_DMA_ADDRESS is the highest address used for ZONE_DMA / GFP_DMA
Does ISA_DMA_THRESHOLD have any meaning on ARM? If you use old ISA stuff then
you need CONFIG_ZONE_DMA and therefore also MAX_DMA_ADDRESS.
If not then there is no need to define CONFIG_ZONE_DMA and MAX_DMA_ADDRESS
looses its usual meaning.
next prev parent reply other threads:[~2008-09-30 19:57 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1222230419-15661-21-git-send-email-nico@cam.org>
[not found] ` <1222230592-15868-1-git-send-email-nico@cam.org>
[not found] ` <20080930162809.GD15911@flint.arm.linux.org.uk>
[not found] ` <alpine.LFD.2.00.0809301409230.3635@xanadu.home>
[not found] ` <20080930184411.GJ15911@flint.arm.linux.org.uk>
2008-09-30 19:35 ` wrong usage of MAX_DMA_ADDRESS in bootmem.h Nicolas Pitre
2008-09-30 19:56 ` Christoph Lameter [this message]
2008-09-30 20:12 ` Russell King - ARM Linux
2008-09-30 21:09 ` Nicolas Pitre
2008-10-01 12:07 ` Christoph Lameter
2008-10-01 14:06 ` Russell King - ARM Linux
2008-10-01 14:50 ` Christoph Lameter
2008-10-01 15:02 ` Russell King - ARM Linux
2008-10-02 16:49 ` Christoph Lameter
2008-10-02 19:06 ` Russell King - ARM Linux
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