linux-kernel - Re: [PATCH v4 05/11] swiotlb: add swiotlb_set_default

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Date:	Tue, 16 Mar 2010 06:58:41 +0100
From:	Albert Herranz <albert_herranz@...oo.es>
To:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
CC:	linux-usb@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org, x86@...nel.org,
	linux-ia64@...r.kernel.org
Subject: Re: [PATCH v4 05/11] swiotlb: add swiotlb_set_default_size()

FUJITA Tomonori wrote:
> On Fri, 12 Mar 2010 20:12:40 +0100
> Albert Herranz <albert_herranz@...oo.es> wrote:
> 
>> The current SWIOTLB code uses a default of 64MB for the IO TLB area.
>> This size can be influenced using a kernel command line parameter "swiotlb".
>> Unfortunately, the parsing of the kernel command line is done _after_ the
>> swiotlb is initialized on some architectures.
>>
>> This patch adds a new function swiotlb_set_default_size() which can be used
>> before swiotlb_init() to indicate the desired IO TLB area size in bytes.
>>
>> This will be used later to implement a smaller IO TLB on the Nintendo Wii
>> video game console which just comes with 24MB + 64MB of RAM.
>>
>> CC: linuxppc-dev@...ts.ozlabs.org
>> CC: linux-kernel@...r.kernel.org
>> CC: x86@...nel.org
>> CC: linux-ia64@...r.kernel.org
>> Signed-off-by: Albert Herranz <albert_herranz@...oo.es>
>> ---
>>  include/linux/swiotlb.h |    2 ++
>>  lib/swiotlb.c           |   20 ++++++++++++++++++++
>>  2 files changed, 22 insertions(+), 0 deletions(-)
> 
> Please fix the powerpc swiotlb initialization instead.
> 
> Calling swiotlb_init() before parsing kernel parameters sounds
> wrong. Any reasons why you can't fix it?
> 

I think that this would be better asked by a PowerPC maintainer. Ben?

If this is really a problem the swiotlb late init may be a solution too in this particular case.

Thanks,
Albert
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