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

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Message-ID: <1465748767.7945.77.camel@edumazet-glaptop3.roam.corp.google.com>
Date:	Sun, 12 Jun 2016 09:26:07 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Feng Tang <feng.tang@...el.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Johannes Berg <johannes@...solutions.net>,
	Jarod Wilson <jarod@...hat.com>, netdev@...r.kernel.org
Subject: Re: [PATCH] net: alx: Work around the DMA RX overflow issue

On Sun, 2016-06-12 at 17:36 +0800, Feng Tang wrote:
> 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>
> ---
>  drivers/net/ethernet/atheros/alx/alx.h  |  4 ---
>  drivers/net/ethernet/atheros/alx/main.c | 61 ++++++++-------------------------
>  2 files changed, 14 insertions(+), 51 deletions(-)

Acked-by: Eric Dumazet <edumazet@...gle.com>

Thanks !