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From:   Sasha Levin <sashal@kernel.org>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc:     Esben Haabendal <esben@geanix.com>,
        "David S . Miller" <davem@davemloft.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.9 68/71] net: ll_temac: Avoid ndo_start_xmit returning NETDEV_TX_BUSY
Date:   Mon, 28 Jun 2021 10:40:00 -0400
Message-Id: <20210628144003.34260-69-sashal@kernel.org>
In-Reply-To: <20210628144003.34260-1-sashal@kernel.org>
References: <20210628144003.34260-1-sashal@kernel.org>
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From: Esben Haabendal <esben@geanix.com>

[ Upstream commit f6396341194234e9b01cd7538bc2c6ac4501ab14 ]

As documented in Documentation/networking/driver.rst, the ndo_start_xmit
method must not return NETDEV_TX_BUSY under any normal circumstances, and
as recommended, we simply stop the tx queue in advance, when there is a
risk that the next xmit would cause a NETDEV_TX_BUSY return.

Signed-off-by: Esben Haabendal <esben@geanix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/ethernet/xilinx/ll_temac_main.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/ethernet/xilinx/ll_temac_main.c b/drivers/net/ethernet/xilinx/ll_temac_main.c
index 545f60877bb7..9ba36c930ce3 100644
--- a/drivers/net/ethernet/xilinx/ll_temac_main.c
+++ b/drivers/net/ethernet/xilinx/ll_temac_main.c
@@ -735,6 +735,11 @@ temac_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 	/* Kick off the transfer */
 	lp->dma_out(lp, TX_TAILDESC_PTR, tail_p); /* DMA start */
 
+	if (temac_check_tx_bd_space(lp, MAX_SKB_FRAGS + 1)) {
+		netdev_info(ndev, "%s -> netif_stop_queue\n", __func__);
+		netif_stop_queue(ndev);
+	}
+
 	return NETDEV_TX_OK;
 }
 
-- 
2.30.2