linux-kernel - [PATCH net v4 2/2] net: mana: Use the correct WQE count for ringing RQ doorbell

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Message-Id: <1688076571-24938-3-git-send-email-longli@linuxonhyperv.com>
Date:   Thu, 29 Jun 2023 15:09:31 -0700
From:   longli@...uxonhyperv.com
To:     "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Leon Romanovsky <leon@...nel.org>,
        Shradha Gupta <shradhagupta@...ux.microsoft.com>,
        Ajay Sharma <sharmaajay@...rosoft.com>,
        Shachar Raindel <shacharr@...rosoft.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        linux-hyperv@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     linux-rdma@...r.kernel.org, Long Li <longli@...rosoft.com>,
        stable@...r.kernel.org
Subject: [PATCH net v4 2/2] net: mana: Use the correct WQE count for ringing RQ doorbell

From: Long Li <longli@...rosoft.com>

The hardware specification specifies that WQE_COUNT should set to 0 for
the Receive Queue. Although currently the hardware doesn't enforce the
check, in the future releases it may check on this value.

Cc: stable@...r.kernel.org
Fixes: ca9c54d2d6a5 ("net: mana: Add a driver for Microsoft Azure Network Adapter (MANA)")
Reviewed-by: Haiyang Zhang <haiyangz@...rosoft.com>
Reviewed-by: Dexuan Cui <decui@...rosoft.com>
Signed-off-by: Long Li <longli@...rosoft.com>
---
Change log:
v4:
Split the original patch into two: one for batching doorbell, one for setting the correct wqe count

 drivers/net/ethernet/microsoft/mana/gdma_main.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/microsoft/mana/gdma_main.c b/drivers/net/ethernet/microsoft/mana/gdma_main.c
index 8f3f78b68592..3765d3389a9a 100644
--- a/drivers/net/ethernet/microsoft/mana/gdma_main.c
+++ b/drivers/net/ethernet/microsoft/mana/gdma_main.c
@@ -300,8 +300,11 @@ static void mana_gd_ring_doorbell(struct gdma_context *gc, u32 db_index,
 
 void mana_gd_wq_ring_doorbell(struct gdma_context *gc, struct gdma_queue *queue)
 {
+	/* Hardware Spec specifies that software client should set 0 for
+	 * wqe_cnt for Receive Queues. This value is not used in Send Queues.
+	 */
 	mana_gd_ring_doorbell(gc, queue->gdma_dev->doorbell, queue->type,
-			      queue->id, queue->head * GDMA_WQE_BU_SIZE, 1);
+			      queue->id, queue->head * GDMA_WQE_BU_SIZE, 0);
 }
 
 void mana_gd_ring_cq(struct gdma_queue *cq, u8 arm_bit)
-- 
2.34.1