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Date: Sun, 30 Nov 2014 10:52:19 +0800 From: Wei Yang <weiyang@...ux.vnet.ibm.com> To: Wei Yang <weiyang@...ux.vnet.ibm.com> Cc: netdev@...r.kernel.org, davem@...emloft.net, gideonn@...lanox.com, Eric Dumazet <edumazet@...gle.com>, Amir Vadai <amirv@...lanox.com> Subject: Re: [PATCH net] net/mlx4_en: correct the endianness of doorbell_qpn on big endian platform BTW, I have one confusion in commit 6a4e812, if (ring->bf_enabled && desc_size <= MAX_BF && !bounce && !vlan_tx_tag_present(skb) && send_doorbell) { - tx_desc->ctrl.bf_qpn |= cpu_to_be32(ring->doorbell_qpn); + tx_desc->ctrl.bf_qpn = ring->doorbell_qpn | + cpu_to_be32(real_size); I am curious about why it adds an | with the real_size? I see this code pass is invoked in vlan network. I am not farmiliar with the vlan test. I guess it needs some router with vlan configuration. If you have some suggestion or link on how to test it, I am happy to have a try. On Sun, Nov 30, 2014 at 10:43:51AM +0800, Wei Yang wrote: >In commit 6a4e812 (net/mlx4_en: Avoid calling bswap in tx fast path), we store >doorbell_qpn in big endian to avoid bswap(). Then we try to write it directly >by iowrite32() instead of iowrite32be(). > >This works fine on little endian platform, while has some problem on big >endian platform. Here is the definition in general: > > #define iowrite32(v, addr) writel((v), (addr)) > #define writel(b,addr) __raw_writel(__cpu_to_le32(b),addr) > >On little endian platform, the value is not swapped before write. While on big >endian platform, the value is swapped. This is not expected to happen. > >This patch does the swap on big endian platform before it is written. > >Signed-off-by: Wei Yang <weiyang@...ux.vnet.ibm.com> >CC: Eric Dumazet <edumazet@...gle.com> >CC: Amir Vadai <amirv@...lanox.com> >--- > drivers/net/ethernet/mellanox/mlx4/en_tx.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > >diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c b/drivers/net/ethernet/mellanox/mlx4/en_tx.c >index 454d9fe..76f028b 100644 >--- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c >+++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c >@@ -954,7 +954,7 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev) > tx_desc->ctrl.owner_opcode = op_own; > if (send_doorbell) { > wmb(); >- iowrite32(ring->doorbell_qpn, >+ iowrite32(__cpu_to_le32(ring->doorbell_qpn), > ring->bf.uar->map + MLX4_SEND_DOORBELL); > } else { > ring->xmit_more++; >-- >1.7.9.5 -- Richard Yang Help you, Help me -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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