From: Philippe De Muyter <phdm@macqel.be>
To: Stany MARCEL <smarcel@pactenovation.fr>
Cc: Greg Ungerer <gerg@snapgear.com>,
linux-m68k@vger.kernel.org, gerg@uclinux.org
Subject: Re: [PATCH 3/4 V2] Add for MCF54xx a virtual non cached zone usable for data exchange with DMA
Date: Tue, 16 Oct 2012 13:23:49 +0200 [thread overview]
Message-ID: <20121016112349.GA30393@frolo.macqel> (raw)
In-Reply-To: <1512C13C0C5EA947AE50B9B9AC314F4701B00E1D@ATLAS.pactenovation.fr>
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@snapgear.com]
> Sent: Tue 10/16/2012 7:15 AM
> To: Stany MARCEL
> Cc: linux-m68k@vger.kernel.org; gerg@uclinux.org
> 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
next prev parent reply other threads:[~2012-10-16 11:23 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-15 12:54 [PATCH 1/4] Add linux/io.h to make it compile Stany MARCEL
2012-10-15 12:54 ` [PATCH 2/4] Permit to read/write to shared page Stany MARCEL
2012-10-15 12:54 ` [PATCH 3/4] Add for MCF54xx a virtual non cached zone usable for data exchange with DMA Stany MARCEL
2012-10-15 13:22 ` [PATCH 3/4 V2] " Stany MARCEL
2012-10-16 5:15 ` Greg Ungerer
2012-10-16 10:46 ` Stany MARCEL
2012-10-16 11:23 ` Philippe De Muyter [this message]
2012-10-16 12:29 ` Greg Ungerer
2012-10-16 13:57 ` RE : " Stany MARCEL
2012-10-15 12:54 ` [PATCH 4/4] Set ACR1 cache mode depending on kernel configuration Stany MARCEL
2012-10-15 13:22 ` [PATCH 4/4 V2] " Stany MARCEL
2012-10-16 5:27 ` Greg Ungerer
2012-10-16 8:12 ` Philippe De Muyter
2012-10-16 12:06 ` Greg Ungerer
2012-10-15 13:58 ` [PATCH 1/4] Add linux/io.h to make it compile Philippe De Muyter
2012-10-15 14:06 ` Stany MARCEL
2012-10-15 14:39 ` Philippe De Muyter
2012-10-16 4:58 ` Greg Ungerer
2012-10-15 14:08 ` [PATCH 1/4 V2] Add linux/io.h to make m54xx_wdt.c compile with MMU enabled Stany MARCEL
2012-10-16 5:04 ` Greg Ungerer
2012-10-16 10:47 ` Stany MARCEL
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