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https://github.com/mmueller41/genode.git
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ff128df131
Unfortunately, our current implementation of 'wmb()' doesn't seem to do what we want it to do. On base-hw + imx6q_sabrelite, the write of bdp->cbd_sc seems to get re-ordered after the write to txq->bd.reg_desc_active in the transmission path of the contrib code. Due to this, the transmission of the packet is only triggered the next time a packet is sent. However, we only quick-fix it by enforcing the execution of the write with a volatile global read as we will soon update the FEC NIC port with a new DDE approach anyway. Fixes #4010
44 lines
1.7 KiB
Diff
44 lines
1.7 KiB
Diff
diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
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index 3f72629..2b54f2b 100644
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--- a/drivers/net/ethernet/freescale/fec_main.c
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+++ b/drivers/net/ethernet/freescale/fec_main.c
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@@ -428,7 +428,7 @@ static int fec_enet_txq_submit_skb(struct fec_enet_priv_tx_q *txq,
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{
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struct fec_enet_private *fep = netdev_priv(ndev);
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int nr_frags = skb_shinfo(skb)->nr_frags;
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- struct bufdesc *bdp, *last_bdp;
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+ struct bufdesc *bdp, *last_bdp, *dummy_bdp;
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void *bufaddr;
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dma_addr_t addr;
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unsigned short status;
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@@ -532,6 +532,7 @@ static int fec_enet_txq_submit_skb(struct fec_enet_priv_tx_q *txq,
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*/
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status |= (BD_ENET_TX_READY | BD_ENET_TX_TC);
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bdp->cbd_sc = cpu_to_fec16(status);
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+ dummy_bdp = bdp;
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/* If this was the last BD in the ring, start at the beginning again. */
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bdp = fec_enet_get_nextdesc(last_bdp, &txq->bd);
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@@ -542,6 +543,21 @@ static int fec_enet_txq_submit_skb(struct fec_enet_priv_tx_q *txq,
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* txq->bd.cur.
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*/
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wmb();
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+
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+ /*
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+ * Unfortunately, our current implementation of 'wmb()' doesn't seem
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+ * to do what we want it to do. On base-hw + imx6q_sabrelite, the
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+ * write of bdp->cbd_sc seems to get re-ordered after the write to
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+ * txq->bd.reg_desc_active and, therefore, the transmission of the packet
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+ * would only be triggered the next time we reach this point,
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+ * i.e. when the next packet is sent. However, we only quick-fix it by
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+ * enforcing the write with this volatile global read as we will
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+ * soon update the FEC NIC port with a new DDE approach anyway
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+ * (See Genode Github issue #4010).
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+ */
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+ static unsigned long volatile dummy_cbd_sc;
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+ dummy_cbd_sc = *(unsigned long volatile *)&dummy_bdp->cbd_sc;
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+
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txq->bd.cur = bdp;
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/* Trigger transmission start */
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