netdev - Re: [PATCH net 1/1] net: fec: update dirty

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Date:	Sat, 7 May 2016 11:56:50 -0700
From:	Troy Kisky <troy.kisky@...ndarydevices.com>
To:	Fugang Duan <fugang.duan@....com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"lznuaa@...il.com" <lznuaa@...il.com>
Cc:	Fabio Estevam <fabio.estevam@....com>,
	"l.stach@...gutronix.de" <l.stach@...gutronix.de>,
	"andrew@...n.ch" <andrew@...n.ch>,
	"tremyfr@...il.com" <tremyfr@...il.com>,
	"gerg@...inux.org" <gerg@...inux.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"johannes@...solutions.net" <johannes@...solutions.net>,
	"stillcompiling@...il.com" <stillcompiling@...il.com>,
	"sergei.shtylyov@...entembedded.com" 
	<sergei.shtylyov@...entembedded.com>,
	"arnd@...db.de" <arnd@...db.de>,
	"holgerschurig@...il.com" <holgerschurig@...il.com>
Subject: Re: [PATCH net 1/1] net: fec: update dirty_tx even if no skb

On 4/21/2016 10:59 PM, Fugang Duan wrote:
> From: Troy Kisky <troy.kisky@...ndarydevices.com> Sent: Friday, April 22, 2016 10:01 AM
>> To: netdev@...r.kernel.org; davem@...emloft.net; Fugang Duan
>> <fugang.duan@....com>; lznuaa@...il.com
>> Cc: Fabio Estevam <fabio.estevam@....com>; l.stach@...gutronix.de;
>> andrew@...n.ch; tremyfr@...il.com; gerg@...inux.org; linux-arm-
>> kernel@...ts.infradead.org; johannes@...solutions.net;
>> stillcompiling@...il.com; sergei.shtylyov@...entembedded.com;
>> arnd@...db.de; holgerschurig@...il.com; Troy Kisky
>> <troy.kisky@...ndarydevices.com>
>> Subject: [PATCH net 1/1] net: fec: update dirty_tx even if no skb
>>
>> If dirty_tx isn't updated, then dma_unmap_single will be called twice.
>>
>> This fixes a
>> [   58.420980] ------------[ cut here ]------------
>> [   58.425667] WARNING: CPU: 0 PID: 377 at /home/schurig/d/mkarm/linux-
>> 4.5/lib/dma-debug.c:1096 check_unmap+0x9d0/0xab8()
>> [   58.436405] fec 2188000.ethernet: DMA-API: device driver tries to free DMA
>> memory it has not allocated [device address=0x0000000000000000] [size=66
>> bytes]
>>
>> encountered by Holger
>>
>> Signed-off-by: Troy Kisky <troy.kisky@...ndarydevices.com>
>> Tested-by: <holgerschurig@...il.com>
>> ---
>>  drivers/net/ethernet/freescale/fec_main.c | 8 +++-----
>>  1 file changed, 3 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/freescale/fec_main.c
>> b/drivers/net/ethernet/freescale/fec_main.c
>> index 08243c2..b71654c 100644
>> --- a/drivers/net/ethernet/freescale/fec_main.c
>> +++ b/drivers/net/ethernet/freescale/fec_main.c
>> @@ -1197,10 +1197,8 @@ fec_enet_tx_queue(struct net_device *ndev, u16
>> queue_id)
>>  					 fec16_to_cpu(bdp->cbd_datlen),
>>  					 DMA_TO_DEVICE);
>>  		bdp->cbd_bufaddr = cpu_to_fec32(0);
>> -		if (!skb) {
>> -			bdp = fec_enet_get_nextdesc(bdp, &txq->bd);
>> -			continue;
>> -		}
>> +		if (!skb)
>> +			goto skb_done;
>>
>>  		/* Check for errors. */
>>  		if (status & (BD_ENET_TX_HB | BD_ENET_TX_LC | @@ -1239,7
>> +1237,7 @@ fec_enet_tx_queue(struct net_device *ndev, u16 queue_id)
>>
>>  		/* Free the sk buffer associated with this last transmit */
>>  		dev_kfree_skb_any(skb);
>> -
>> +skb_done:
>>  		/* Make sure the update to bdp and tx_skbuff are performed
>>  		 * before dirty_tx
>>  		 */
>> --
>> 2.5.0
> 
> The patch is fine for me.
> Can you review below patch that also fix the issue. It can take much effort due to less rmb() and READ_ONCE() operation that is very sensitive for duplex Gbps test for i.MX6SX/i.MX7d SOC. (i.MX6SX can reach at 1.4Gbps, i.MX7D can reach at 1.8Gbps.)
> 


Am I supposed to do anything else to get this patch into net ?