linux-kernel - Re: [PATCH 2/2] arch: m68k: Add DMA mapping operations for Coldfire M5441x

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Message-ID: <ba7ea0f0-be38-49a7-b416-3dc62c7e7425@yoseli.org>
Date: Tue, 28 Jan 2025 07:33:37 +0100
From: Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org>
To: Christoph Hellwig <hch@...radead.org>
Cc: Geert Uytterhoeven <geert@...ux-m68k.org>,
 Greg Ungerer <gerg@...ux-m68k.org>, linux-m68k@...ts.linux-m68k.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] arch: m68k: Add DMA mapping operations for Coldfire
 M5441x

Hi Christoph,

On 28/01/2025 07:10, Christoph Hellwig wrote:
> On Tue, Jan 21, 2025 at 11:54:14AM +0100, Jean-Michel Hautbois wrote:
>> Introduce `dma_ops` for the Coldfire M5441x platform, enabling both
>> coherent and streaming DMA operations. This addition should fill the gap
>> for DMA support integrates with the existing kernel DMA framework.
> 
> Arch dma code should not implement DMA OPS, but use the generic
> dma-direct code with the right helpes for handling coherency.  This
> variant looks like it should be using the DMA_COHERENT_POOL allocator
> for dma coherent memory.

Thanks for your answer.
I am not sure to understand it though :-) because I can see a few 
dma_map_ops implementations in arch code. I tried to let dma_direct do 
the work, I can't remember exactly what happened but it was not great :-).
I can give it a second try.

Thanks,
JM