[PATCH net-next V2 07/16] net: fec: set cbd_sc without relying on previous value

[Fugang Duan]

 From: Troy Kisky <troy.kisky at boundarydevices.com> Sent: Saturday, March 05, 2016 12:08 AM
> To: Fugang Duan <fugang.duan at nxp.com>; netdev at vger.kernel.org;
> davem at davemloft.net; b38611 at freescale.com
> Cc: fabio.estevam at freescale.com; l.stach at pengutronix.de; andrew at lunn.ch;
> tremyfr at gmail.com; linux at arm.linux.org.uk; linux-arm-
> kernel at lists.infradead.org; laci at boundarydevices.com; shawnguo at kernel.org;
> johannes at sipsolutions.net; stillcompiling at gmail.com;
> sergei.shtylyov at cogentembedded.com; arnd at arndb.de
> Subject: Re: [PATCH net-next V2 07/16] net: fec: set cbd_sc without relying on
> previous value
> 
> On 3/4/2016 2:29 AM, Fugang Duan wrote:
> > From: Troy Kisky <troy.kisky at boundarydevices.com> Sent: Thursday,
> > February 25, 2016 8:37 AM
> >> To: netdev at vger.kernel.org; davem at davemloft.net;
> b38611 at freescale.com
> >> Cc: fabio.estevam at freescale.com; l.stach at pengutronix.de;
> >> andrew at lunn.ch; tremyfr at gmail.com; linux at arm.linux.org.uk; linux-arm-
> >> kernel at lists.infradead.org; laci at boundarydevices.com;
> >> shawnguo at kernel.org; johannes at sipsolutions.net;
> >> stillcompiling at gmail.com; sergei.shtylyov at cogentembedded.com;
> >> arnd at arndb.de; Troy Kisky <troy.kisky at boundarydevices.com>
> >> Subject: [PATCH net-next V2 07/16] net: fec: set cbd_sc without
> >> relying on previous value
> >>
> >> Relying on the wrap bit to stay valid once initialized when the
> >> controller also writes to this byte seems undesirable since we can
> >> easily know what the value should be.
> >>
> >> Signed-off-by: Troy Kisky <troy.kisky at boundarydevices.com>
> >> ---
> >>  drivers/net/ethernet/freescale/fec_main.c | 38
> >> +++++++++----------------------
> >>  1 file changed, 11 insertions(+), 27 deletions(-)
> >>
> >> diff --git a/drivers/net/ethernet/freescale/fec_main.c
> >> b/drivers/net/ethernet/freescale/fec_main.c
> >> index 791f385..6ceb5f9 100644
> >> --- a/drivers/net/ethernet/freescale/fec_main.c
> >> +++ b/drivers/net/ethernet/freescale/fec_main.c
> >> @@ -340,9 +340,8 @@ fec_enet_txq_submit_frag_skb(struct
> >> fec_enet_priv_tx_q *txq,
> >>  		bdp = fec_enet_get_nextdesc(bdp, &txq->bd);
> >>  		ebdp = (struct bufdesc_ex *)bdp;
> >>
> >> -		status = fec16_to_cpu(bdp->cbd_sc);
> >> -		status &= ~BD_ENET_TX_STATS;
> >> -		status |= (BD_ENET_TX_TC | BD_ENET_TX_READY);
> >> +		status = BD_ENET_TX_TC | BD_ENET_TX_READY |
> >> +				((bdp == txq->bd.last) ? BD_SC_WRAP : 0);
> >>  		frag_len = skb_shinfo(skb)->frags[frag].size;
> >>
> >>  		/* Handle the last BD specially */ @@ -436,8 +435,6 @@ static
> int
> >> fec_enet_txq_submit_skb(struct fec_enet_priv_tx_q *txq,
> >>  	/* Fill in a Tx ring entry */
> >>  	bdp = txq->bd.cur;
> >>  	last_bdp = bdp;
> >> -	status = fec16_to_cpu(bdp->cbd_sc);
> >> -	status &= ~BD_ENET_TX_STATS;
> >>
> >>  	/* Set buffer length and buffer pointer */
> >>  	bufaddr = skb->data;
> >> @@ -462,6 +459,8 @@ static int fec_enet_txq_submit_skb(struct
> >> fec_enet_priv_tx_q *txq,
> >>  		return NETDEV_TX_OK;
> >>  	}
> >>
> >> +	status = BD_ENET_TX_TC | BD_ENET_TX_READY |
> >> +			((bdp == txq->bd.last) ? BD_SC_WRAP : 0);
> >>  	if (nr_frags) {
> >>  		last_bdp = fec_enet_txq_submit_frag_skb(txq, skb, ndev);
> >>  		if (IS_ERR(last_bdp)) {
> >> @@ -512,7 +511,6 @@ static int fec_enet_txq_submit_skb(struct
> >> fec_enet_priv_tx_q *txq,
> >>  	/* Send it on its way.  Tell FEC it's ready, interrupt when done,
> >>  	 * it's the last BD of the frame, and to put the CRC on the end.
> >>  	 */
> >> -	status |= (BD_ENET_TX_READY | BD_ENET_TX_TC);
> >
> > This is completely error.  We have to prepare all BDs for frag skb, and then
> enable "READY" and "TC" bit for the first BD, otherwise uDMA copy un-correct
> data to fifo.
> >
> 
> 
> 
> 
> I don't follow. Please read patch again.
> 
Understand, sorry, I take one mistake.  The patch is fine for me.