netdev - Re: [PATCH v1 1/1 net] net: fec: workaround stop tx during errata ERR006358

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Date:	Sat, 27 Jul 2013 20:15:18 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	B38611@...escale.com
Cc:	B20596@...escale.com, shawn.guo@...aro.org, netdev@...r.kernel.org,
	l.stach@...gutronix.de, r.schwebel@...gutronix.de, lznuaa@...il.com
Subject: Re: [PATCH v1 1/1 net] net: fec: workaround stop tx during errata
 ERR006358

From: Duan Fugang-B38611 <B38611@...escale.com>
Date: Thu, 25 Jul 2013 08:16:23 +0000

> On 25/07/13 14:06, Li Frank wrote:
>>If the ready bit in the transmit buffer descriptor (TxBD[R]) is previously detected as not set during a prior frame transmission, then the ENET_TDAR[TDAR] bit is cleared at a later time, even if additional TxBDs were added to the ring and the ENET_TDAR[TDAR] bit is set. This results in frames not being transmitted until there is a 0-to-1 transition on ENET_TDAR[TDAR].
>>
>>Workarounds:
>>code can use the transmit frame interrupt flag (ENET_EIR[TXF]) as a method to detect whether the ENET has completed transmission and the ENET_TDAR[TDAR] has been cleared. If ENET_TDAR[TDAR] is detected as cleared when packets are queued and waiting for transmit, then a write to the TDAR bit will restart TxBD processing.
>>
>>This case main happen when loading is light. A ethernet package may not send out utile next package put into tx queue.
>>
>>How to test:
>>while [ true ]
>>do
>>	ping <IP> -s 10000 -w 4
>>	ping <IP> -s 6000 -w 2
>>	ping <IP> -s 4000 -w 2
>>	ping <IP> -s 10000 -w 2
>>done
>>
>>You will see below result in overnight test.
>>
>>6008 bytes from 10.192.242.116: seq=1 ttl=128 time=0.722 ms
>>4008 bytes from 10.192.242.116: seq=0 ttl=128 time=1001.008 ms
>>4008 bytes from 10.192.242.116: seq=1 ttl=128 time=1.010 ms
>>10008 bytes from 10.192.242.116: seq=0 ttl=128 time=0.896 ms
>>
>>After apply this patch, >1000ms delay disappear.
>>
>>Signed-off-by: Frank Li <Frank.Li@...escale.com>
> 
> Acked-by: Fugang Duan  <B38611@...escale.com>

Applied, thanks.
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