netdev - RE: [PATCH] net/fec: call netif_carrier

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Date:	Fri, 26 Jul 2013 09:35:03 +0000
From:	Duan Fugang-B38611 <B38611@...escale.com>
To:	Stephen Hemminger <stephen@...workplumber.org>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Estevam Fabio-R49496 <r49496@...escale.com>,
	Li Frank-B20596 <B20596@...escale.com>,
	Shawn Guo <shawn.guo@...aro.org>,
	"kernel@...gutronix.de" <kernel@...gutronix.de>,
	Hector Palacios <hector.palacios@...i.com>,
	Tim Sander <tim.sander@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: RE: [PATCH] net/fec: call netif_carrier_off when not having link

On Fir, 26 Jul 2013 12:04, Stephen Hemminger wrote:
>> diff --git a/drivers/net/ethernet/freescale/fec_main.c 
>> b/drivers/net/ethernet/freescale/fec_main.c
>> index 0642006..631bd5a 100644
>> --- a/drivers/net/ethernet/freescale/fec_main.c
>> +++ b/drivers/net/ethernet/freescale/fec_main.c
>> @@ -280,11 +280,6 @@ fec_enet_start_xmit(struct sk_buff *skb, struct net_device *ndev)
>>  	unsigned short	status;
>>  	unsigned int index;
>>  
>> -	if (!fep->link) {
>> -		/* Link is down or auto-negotiation is in progress. */
>> -		return NETDEV_TX_BUSY;
>> -	}
>> -
>
>That is a bug anyway. Since it would cause spin loop in transmit code (even without -rt).
>If the driver cared to test it (most drivers just let hardware deal with this situation),
>then it should free packet and return TX_OK.

When link is down, the logic is
	- call netif_stop_queue() to stop queue
	- and then notify there have no link using netif_carrier_off().

But the flow must be handled in fec_enet_adjust_link() function, not in xmit().


Thanks,
Andy

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