netdev - Re: [PATCH] net: alx: Work around the DMA RX overflow issue

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Message-Id: <20160614.153154.267530721453507462.davem@davemloft.net>
Date:	Tue, 14 Jun 2016 15:31:54 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	feng.tang@...el.com
Cc:	eric.dumazet@...il.com, johannes@...solutions.net,
	jarod@...hat.com, netdev@...r.kernel.org
Subject: Re: [PATCH] net: alx: Work around the DMA RX overflow issue

From: Feng Tang <feng.tang@...el.com>
Date: Sun, 12 Jun 2016 17:36:37 +0800

> Commit 26c5f03 uses a new skb allocator to avoid the RFD overflow
> issue.
> 
> But from debugging without datasheet, we found the error always
> happen when the DMA RX address is set to 0x....fc0, which is very
> likely to be a HW/silicon problem.
> 
> So one idea is instead of adding a new allocator, why not just
> hitting the right target by avaiding the error-prone DMA address?
> 
> This patch will actually
> * Remove the commit 26c5f03
> * Apply rx skb with 64 bytes longer space, and if the allocated skb
>   has a 0x...fc0 address, it will use skb_resever(skb, 64) to
>   advance the address, so that the RX overflow can be avoided.
> 
> In theory this method should also apply to atl1c driver, which
> I can't find anyone who can help to test on real devices.
> 
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=70761
> Signed-off-by: Feng Tang <feng.tang@...el.com>
> Suggested-by: Eric Dumazet <edumazet@...gle.com>
> Tested-by: Ole Lukoie <olelukoie@...l.ru>

Applied.