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

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Message-ID: <2627cc80-f431-b47c-68aa-fc818785808f@gmail.com>
Date: Fri, 13 Oct 2023 08:18:32 +1300
From: Michael Schmitz <schmitzmic@...il.com>
To: Greg Ungerer <gerg@...ux-m68k.org>, 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

Hi Greg,

On 13/10/23 02:25, Greg Ungerer wrote:
> Hi Michael,
>
> On 12/10/23 04:21, Michael Schmitz wrote:
>> Hi Greg,
>>
>> On 12/10/23 02:09, Greg Ungerer wrote:
>>>
>>> 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)
>>
>> You appear to have dropped a '!' there ...
>
> Not sure I follow. This is the opposite of the case above. The 
> noncoherent alloc
> and cache flush should be performed if ColdFire and any of 
> CONFIG_HAVE_CACHE_CB,
> CONFIG_CACHE_D or CONFIG_CACHE_BOTH are set - since that means there 
> is data
> caching involved.

Now I see - I had read that definition to correspond to the 'select 
coherent allocations on m68k' case, not the latter 'use non-coherent 
allocations in the fec driver'.

Your definitions are correct as written (and for all I can see, 
Christoph's implementation is correct, too).

Apologies for the noise - I blame jet leg for getting my wires crossed ...

Cheers,

     Michael

>
> Regards
> Greg
>