| Message ID | 1425343920.4288.9.camel@xylophone.i.decadent.org.uk |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
Hello. On 03/03/2015 03:52 AM, Ben Hutchings wrote: > When submitting a DMA descriptor, the active bit must be written last. > When reading a completed DMA descriptor, the active bit must be read > first. > Add memory barriers to ensure that this ordering is maintained. Looks like those should have been lighter dma_rmb() and dma_wmb() instead. Correct, Alexander? > Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk> > --- > drivers/net/ethernet/renesas/sh_eth.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/net/ethernet/renesas/sh_eth.c b/drivers/net/ethernet/renesas/sh_eth.c > index 654b48d1e61a..5c212a833bcf 100644 > --- a/drivers/net/ethernet/renesas/sh_eth.c > +++ b/drivers/net/ethernet/renesas/sh_eth.c > @@ -1410,6 +1410,8 @@ static int sh_eth_txfree(struct net_device *ndev) > txdesc = &mdp->tx_ring[entry]; > if (txdesc->status & cpu_to_edmac(mdp, TD_TACT)) > break; > + /* TACT bit must be checked before all the following reads */ > + rmb(); > /* Free the original skb. */ > if (mdp->tx_skbuff[entry]) { > dma_unmap_single(&ndev->dev, txdesc->addr, > @@ -1447,6 +1449,8 @@ static int sh_eth_rx(struct net_device *ndev, u32 intr_status, int *quota) > limit = boguscnt; > rxdesc = &mdp->rx_ring[entry]; > while (!(rxdesc->status & cpu_to_edmac(mdp, RD_RACT))) { > + /* RACT bit must be checked before all the following reads */ > + rmb(); > desc_status = edmac_to_cpu(mdp, rxdesc->status); > pkt_len = rxdesc->frame_length; > > @@ -1526,6 +1530,7 @@ static int sh_eth_rx(struct net_device *ndev, u32 intr_status, int *quota) > skb_checksum_none_assert(skb); > rxdesc->addr = dma_addr; > } > + wmb(); /* RACT bit must be set after all the above writes */ > if (entry >= mdp->num_rx_ring - 1) > rxdesc->status |= > cpu_to_edmac(mdp, RD_RACT | RD_RFP | RD_RDEL); > @@ -2195,6 +2200,7 @@ static int sh_eth_start_xmit(struct sk_buff *skb, struct net_device *ndev) > } > txdesc->buffer_length = skb->len; > > + wmb(); /* TACT bit must be set after all the above writes */ > if (entry >= mdp->num_tx_ring - 1) > txdesc->status |= cpu_to_edmac(mdp, TD_TACT | TD_TDLE); > else WBR, Sergei -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Fri, 2015-04-10 at 01:21 +0300, Sergei Shtylyov wrote: > Hello. > > On 03/03/2015 03:52 AM, Ben Hutchings wrote: > > > When submitting a DMA descriptor, the active bit must be written last. > > When reading a completed DMA descriptor, the active bit must be read > > first. > > > Add memory barriers to ensure that this ordering is maintained. > > Looks like those should have been lighter dma_rmb() and dma_wmb() instead. Yes, I think so. I missed those additions to the DMA API. Ben. > Correct, Alexander? > > > Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk> > > --- > > drivers/net/ethernet/renesas/sh_eth.c | 6 ++++++ > > 1 file changed, 6 insertions(+) > > > > diff --git a/drivers/net/ethernet/renesas/sh_eth.c b/drivers/net/ethernet/renesas/sh_eth.c > > index 654b48d1e61a..5c212a833bcf 100644 > > --- a/drivers/net/ethernet/renesas/sh_eth.c > > +++ b/drivers/net/ethernet/renesas/sh_eth.c > > @@ -1410,6 +1410,8 @@ static int sh_eth_txfree(struct net_device *ndev) > > txdesc = &mdp->tx_ring[entry]; > > if (txdesc->status & cpu_to_edmac(mdp, TD_TACT)) > > break; > > + /* TACT bit must be checked before all the following reads */ > > + rmb(); > > /* Free the original skb. */ > > if (mdp->tx_skbuff[entry]) { > > dma_unmap_single(&ndev->dev, txdesc->addr, > > @@ -1447,6 +1449,8 @@ static int sh_eth_rx(struct net_device *ndev, u32 intr_status, int *quota) > > limit = boguscnt; > > rxdesc = &mdp->rx_ring[entry]; > > while (!(rxdesc->status & cpu_to_edmac(mdp, RD_RACT))) { > > + /* RACT bit must be checked before all the following reads */ > > + rmb(); > > desc_status = edmac_to_cpu(mdp, rxdesc->status); > > pkt_len = rxdesc->frame_length; > > > > @@ -1526,6 +1530,7 @@ static int sh_eth_rx(struct net_device *ndev, u32 intr_status, int *quota) > > skb_checksum_none_assert(skb); > > rxdesc->addr = dma_addr; > > } > > + wmb(); /* RACT bit must be set after all the above writes */ > > if (entry >= mdp->num_rx_ring - 1) > > rxdesc->status |= > > cpu_to_edmac(mdp, RD_RACT | RD_RFP | RD_RDEL); > > @@ -2195,6 +2200,7 @@ static int sh_eth_start_xmit(struct sk_buff *skb, struct net_device *ndev) > > } > > txdesc->buffer_length = skb->len; > > > > + wmb(); /* TACT bit must be set after all the above writes */ > > if (entry >= mdp->num_tx_ring - 1) > > txdesc->status |= cpu_to_edmac(mdp, TD_TACT | TD_TDLE); > > else > > WBR, Sergei > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/net/ethernet/renesas/sh_eth.c b/drivers/net/ethernet/renesas/sh_eth.c index 654b48d1e61a..5c212a833bcf 100644 --- a/drivers/net/ethernet/renesas/sh_eth.c +++ b/drivers/net/ethernet/renesas/sh_eth.c @@ -1410,6 +1410,8 @@ static int sh_eth_txfree(struct net_device *ndev) txdesc = &mdp->tx_ring[entry]; if (txdesc->status & cpu_to_edmac(mdp, TD_TACT)) break; + /* TACT bit must be checked before all the following reads */ + rmb(); /* Free the original skb. */ if (mdp->tx_skbuff[entry]) { dma_unmap_single(&ndev->dev, txdesc->addr, @@ -1447,6 +1449,8 @@ static int sh_eth_rx(struct net_device *ndev, u32 intr_status, int *quota) limit = boguscnt; rxdesc = &mdp->rx_ring[entry]; while (!(rxdesc->status & cpu_to_edmac(mdp, RD_RACT))) { + /* RACT bit must be checked before all the following reads */ + rmb(); desc_status = edmac_to_cpu(mdp, rxdesc->status); pkt_len = rxdesc->frame_length; @@ -1526,6 +1530,7 @@ static int sh_eth_rx(struct net_device *ndev, u32 intr_status, int *quota) skb_checksum_none_assert(skb); rxdesc->addr = dma_addr; } + wmb(); /* RACT bit must be set after all the above writes */ if (entry >= mdp->num_rx_ring - 1) rxdesc->status |= cpu_to_edmac(mdp, RD_RACT | RD_RFP | RD_RDEL); @@ -2195,6 +2200,7 @@ static int sh_eth_start_xmit(struct sk_buff *skb, struct net_device *ndev) } txdesc->buffer_length = skb->len; + wmb(); /* TACT bit must be set after all the above writes */ if (entry >= mdp->num_tx_ring - 1) txdesc->status |= cpu_to_edmac(mdp, TD_TACT | TD_TDLE); else
When submitting a DMA descriptor, the active bit must be written last. When reading a completed DMA descriptor, the active bit must be read first. Add memory barriers to ensure that this ordering is maintained. Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk> --- drivers/net/ethernet/renesas/sh_eth.c | 6 ++++++ 1 file changed, 6 insertions(+)