netdev - Re: [PATCH 5/6] net: fec: use dma_alloc

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Date: Wed, 11 Oct 2023 23:09:07 +1000
From: Greg Ungerer <gerg@...ux-m68k.org>
To: Christoph Hellwig <hch@....de>
Cc: Robin Murphy <robin.murphy@....com>, iommu@...ts.linux.dev,
 Marek Szyprowski <m.szyprowski@...sung.com>,
 Geert Uytterhoeven <geert@...ux-m68k.org>, Wei Fang <wei.fang@....com>,
 Shenwei Wang <shenwei.wang@....com>, Clark Wang <xiaoning.wang@....com>,
 NXP Linux Team <linux-imx@....com>, linux-m68k@...ts.linux-m68k.org,
 netdev@...r.kernel.org, Jim Quinlan <james.quinlan@...adcom.com>
Subject: Re: [PATCH 5/6] net: fec: use dma_alloc_noncoherent for m532x


On 11/10/23 15:52, Christoph Hellwig wrote:
> On Wed, Oct 11, 2023 at 12:20:57AM +1000, Greg Ungerer wrote:
>> That should be M532x.
>>
>> I am pretty sure the code as-is today is broken for the case of using
>> the split cache arrangement (so both instruction and data cache) for any
>> of the version 2 cores too (denoted by the HAVE_CACHE_SPLIT option).
>> But that has probably not been picked up because the default on those
>> has always been instruction cache only.
>>
>> The reason for the special case for the M532x series is that it is a version 3
>> core and they have a unified instruction and data cache. The 523x series is the
>> only version 3 core that Linux supports that has the FEC hardware module.
> 
> So what config option should we check for supporting coherent allocations
> and which not having the hack in fec?
> 
> Here is my guesses based on the above:
> 
> in m68k support coherent allocations with no work if
> 
> CONFIG_COLDIFRE is set and neither CONFIG_CACHE_D or CONFIG_CACHE_BOTH
> is set.

I think this needs to be CONFIG_COLDFIRE is set and none of CONFIG_HAVE_CACHE_CB or
CONFIG_CACHE_D or CONFIG_CACHE_BOTH are set.



> in the fec driver do the alloc_noncoherent and global cache flush
> hack if:
> 
> COMFIG_COLDFIRE && (CONFIG_CACHE_D || CONFIG_CACHE_BOTH)

And then this becomes:

CONFIG_COLDFIRE && (CONFIG_HAVE_CACHE_CB || CONFIG_CACHE_D || CONFIG_CACHE_BOTH)