From: Ben Hutchings Date: Tue, 3 Mar 2015 00:52:00 +0000 (+0000) Subject: sh_eth: Ensure proper ordering of descriptor active bit write/read X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=7d7355f58ba4;p=openwrt%2Fstaging%2Fblogic.git sh_eth: Ensure proper ordering of descriptor active bit write/read 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 Signed-off-by: David S. Miller --- 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