RE: [PATCH net 1/1] net: fec: update dirty_tx even if no skb

[Fugang Duan <fugang.duan@nxp.com>]

From: Troy Kisky <troy.kisky@boundarydevices.com> Sent: Friday, April 22, 2016 10:01 AM
> To: netdev@vger.kernel.org; davem@davemloft.net; Fugang Duan
> <fugang.duan@nxp.com>; lznuaa@gmail.com
> Cc: Fabio Estevam <fabio.estevam@nxp.com>; l.stach@pengutronix.de;
> andrew@lunn.ch; tremyfr@gmail.com; gerg@uclinux.org; linux-arm-
> kernel@lists.infradead.org; johannes@sipsolutions.net;
> stillcompiling@gmail.com; sergei.shtylyov@cogentembedded.com;
> arnd@arndb.de; holgerschurig@gmail.com; Troy Kisky
> <troy.kisky@boundarydevices.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@boundarydevices.com>
> Tested-by: <holgerschurig@gmail.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

Thanks. 
Acked-by: Fugang Duan <fugang.duan@nxp.com>