On Fri, 5 Feb 2016 14:52:49 -0700
Troy Kisky <troy.ki...@boundarydevices.com> wrote:
> If you don't own it, you shouldn't write to it.
>
> Signed-off-by: Troy Kisky <troy.ki...@boundarydevices.com>
> ---
> drivers/net/ethernet/freescale/fec_main.c | 14 +++++++++++++-
> 1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/freescale/fec_main.c
> b/drivers/net/ethernet/freescale/fec_main.c index ca2708d..97ca72a
> 100644 --- a/drivers/net/ethernet/freescale/fec_main.c
> +++ b/drivers/net/ethernet/freescale/fec_main.c
> @@ -390,6 +390,10 @@ fec_enet_txq_submit_frag_skb(struct
> fec_enet_priv_tx_q *txq,
> bdp->cbd_bufaddr = cpu_to_fec32(addr);
> bdp->cbd_datlen = cpu_to_fec16(frag_len);
> + /* Make sure the updates to rest of the descriptor
> are
> + * performed before transferring ownership.
> + */
> + wmb();
> bdp->cbd_sc = cpu_to_fec16(status);
You use almost exactly the same code in each place.
I'd prefer to have wmb(); bdp->cbd_sc = cpu_to_fec16(status) wrapped in
a function or function like macro, and put the comment in one place.
e.g.
/* Make sure the updates to rest of the descriptor
* performed before transferring ownership.
*/
#define fec_enet_xfr_ownership(status) \
do { \
wmb();
bdp->cbd_sc = cpu_to_fec16(status);
} while (0)
(I don't know if thats the right macro name, I'm just basing it off
your comment)
> }
>
> @@ -499,6 +503,10 @@ static int fec_enet_txq_submit_skb(struct
> fec_enet_priv_tx_q *txq,
> bdp->cbd_datlen = cpu_to_fec16(buflen);
> bdp->cbd_bufaddr = cpu_to_fec32(addr);
> + /* Make sure the updates to rest of the descriptor are
> performed before
> + * transferring ownership.
> + */
> + wmb();
>
> /* 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. @@ -1475,7 +1483,6 @@ rx_processing_done:
>
> /* Mark the buffer empty */
> status |= BD_ENET_RX_EMPTY;
> - bdp->cbd_sc = cpu_to_fec16(status);
>
> if (fep->bufdesc_ex) {
> struct bufdesc_ex *ebdp = (struct bufdesc_ex
> *)bdp; @@ -1484,6 +1491,11 @@ rx_processing_done:
> ebdp->cbd_prot = 0;
> ebdp->cbd_bdu = 0;
> }
> + /* Make sure the updates to rest of the descriptor
> are
> + * performed before transferring ownership.
> + */
> + wmb();
> + bdp->cbd_sc = cpu_to_fec16(status);
>
> /* Update BD pointer to next entry */
> bdp = fec_enet_get_nextdesc(bdp, &rxq->bd);
