netdev - Re: Alignment issues with freescale FEC driver

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Date:   Fri, 23 Sep 2016 11:39:41 -0700
From:   Eric Nelson <eric@...int.com>
To:     Russell King - ARM Linux <linux@...linux.org.uk>,
        Andrew Lunn <andrew@...n.ch>
Cc:     Eric Dumazet <edumazet@...gle.com>,
        Fugang Duan <fugang.duan@....com>,
        Otavio Salvador <otavio@...ystems.com.br>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Troy Kisky <troy.kisky@...ndarydevices.com>,
        Simone <cjb.sw.nospam@...il.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: Alignment issues with freescale FEC driver

Thanks Russell,

On 09/23/2016 11:30 AM, Russell King - ARM Linux wrote:
> On Fri, Sep 23, 2016 at 08:13:01PM +0200, Andrew Lunn wrote:
>>> Since the hardware requires longword alignment for its' DMA transfers,
>>> aligning the IP header will require a memcpy, right?
>>
>> The vf610 FEC has an SHIFT16 bit in register ENETx_TACC, which inserts
>> two padding bits on transmit. ENETx_RACC has the same.
>>
>> What about your hardware?
> 
> The iMX6 FEC also has that ability - as part of my FEC patch stack from
> ages ago, I implemented support for it.
> 
>   "net:fec: implement almost zero-copy receive path"
> 
> in my public fec-testing branch.
> 
> That patch stack is sadly now totally dead and I've no interest in
> reviving it myself.  There was some interest from others in taking my
> patch stack over, but that went quiet.
> 

I'll take a look and hopefully revive at least part of the patch set.