Hi Stany and Greg,
On Tue, Oct 16, 2012 at 12:46:02PM +0200, Stany MARCEL wrote:
It might not be the usual approach in Linux, but after reading the MCF548x Reference Manual,
I think that is the best approach for this family of MCU.
Maybe we should keep Stany's approach of reserving part of the memory
as uncached and use dma_alloc_coherent() or dma_pool_create().
Have a look at Documentation/DMA-API.txt
Best regards
Philippe
Regards,
Stany
-----Original Message-----
From: Greg Ungerer [mailto:gerg@xxxxxxxxxxxx]
Sent: Tue 10/16/2012 7:15 AM
To: Stany MARCEL
Cc: linux-m68k@xxxxxxxxxxxxxxx; gerg@xxxxxxxxxxx
Subject: Re: [PATCH 3/4 V2] Add for MCF54xx a virtual non cached zone usable for data exchange with DMA
Hi Stany,
On 15/10/12 23:22, Stany MARCEL wrote:
This permit to share data with DMA without caching issues. M54xx DMA bypass
cache so exchanged data must be flushed before DMA operation. But M54xx cache
opperation does not permit to easily flush concerned data. So this patch permit
to have a non cached zone used for GFP_DMA allocated data.
Interesting, but I think this is the wrong approach.
We don't want to bypass the cache. Admittedly the current cache support
code we have for ColdFire is not great, it could be improved a lot. So
lets do that, not work around it.
Regards
Greg
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