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

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Date:	Mon, 9 May 2016 02:00:37 +0000
From:	Fugang Duan <fugang.duan@....com>
To:	Troy Kisky <troy.kisky@...ndarydevices.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

From: Troy Kisky <troy.kisky@...ndarydevices.com> Sent: Sunday, May 08, 2016 2:57 AM
> To: Fugang Duan <fugang.duan@....com>; netdev@...r.kernel.org;
> davem@...emloft.net; 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
> 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 ?

I will ack your patch that is fine into net tree.