Re: [PATCH net] net/mlx4_en: correct the endianness of doorbell_qpn on big endian platform
From: Wei Yang <hidden>
Date: 2014-11-30 02:53:02
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:quoted hunk ↗ jump to hunk
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 <redacted> CC: Eric Dumazet <edumazet@google.com> CC: Amir Vadai <redacted> --- 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