Problem with dma_alloc_coherent at linux-2.6.33-arm1 , withRealView platform,board PBX-A9 and armv7 instructions.

[David Yang]

I have a question: in linux-2.6.28, there is no barriers in the IO accessors.

So,how does it prevent the reorder of the io  instructions?

On Thu, Jul 15, 2010 at 9:17 PM, Catalin Marinas
<catalin.marinas at arm.com> wrote:
> On Thu, 2010-07-15 at 14:10 +0100, David Yang wrote:
>> I have passed the test,when using wmb() and without PATCH 0/3;
>
> Great, so it's a memory ordering issue.
>
>> But,I have a  doubt : if I use the wmb(), then the l2x0.c 's patch is
>> not needed?
>
> Correct, if you add the wmb(), none of the three ordered accessors
> patches are needed. But we'll probably push them anyway, in which case
> the wmb() becomes superfluous.
>
>> I will test the PATCH v3 0/3  tomorrow, without using wmb();
>
> Thanks.
>
> --
> Catalin
>
>