[PATCH 17/19] net/hns3: revert fix mailbox communication with HW

[Dongdong Liu <liudongdong3@huawei.com>]

From: Chengwen Feng <fengchengwen@huawei.com>

VF's command receive queue was mainly used to receive mailbox messages
from PF. There are two type mailbox messages: request response message
and message pushed by PF.

There are two types of threads that can handle these messages:
1) the interrupt thread of the main process: it could handle both types
of messages.
2) other threads: it could only handle request response messages.

The collaboration mechanism between the two type threads is that other
threads set the opcode of processed messages to zero so that the
interrupt thread of the main process does not process these messages
again. Because other threads can only process part of the messages,
after the processing is complete, the next-to-use pointer of the
command receive queue should not be updated. Otherwise, some messages
(e.g. messages pushed by PF) maybe discarded.

Unfortunately, the patch to be reverted updates next-to-use pointer of
the command receive queue in other threads context, and this will lead
to discard some mailbox message.

So this commit reverts
commit 599ef84add7e ("net/hns3: fix mailbox communication with HW")

Fixes: 599ef84add7e ("net/hns3: fix mailbox communication with HW")
Cc: stable@dpdk.org

Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
Signed-off-by: Dongdong Liu <liudongdong3@huawei.com>
---
 drivers/net/hns3/hns3_mbx.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/hns3/hns3_mbx.c b/drivers/net/hns3/hns3_mbx.c
index 02028dcd9c..910a16c999 100644
--- a/drivers/net/hns3/hns3_mbx.c
+++ b/drivers/net/hns3/hns3_mbx.c
@@ -436,8 +436,10 @@ hns3_handle_mbx_msg_out_intr(struct hns3_hw *hw)
 		next_to_use = (next_to_use + 1) % hw->cmq.crq.desc_num;
 	}
 
-	crq->next_to_use = next_to_use;
-	hns3_write_dev(hw, HNS3_CMDQ_RX_HEAD_REG, crq->next_to_use);
+	/*
+	 * Note: the crq->next_to_use field should not updated, otherwise,
+	 * mailbox messages may be discarded.
+	 */
 }
 
 void
-- 
2.22.0