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From:   Esben Haabendal <esben@geanix.com>
To:     netdev@vger.kernel.org
Cc:     "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Michal Simek <michal.simek@xilinx.com>,
        Zhang Changzhong <zhangchangzhong@huawei.com>,
        Andrew Lunn <andrew@lunn.ch>, Michael Walle <michael@walle.cc>,
        Wang Hai <wanghai38@huawei.com>,
        Jesse Brandeburg <jesse.brandeburg@intel.com>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: [PATCH 4/4] net: ll_temac: Avoid ndo_start_xmit returning NETDEV_TX_BUSY
Date:   Fri, 18 Jun 2021 12:52:38 +0200
Message-Id: <4c927f4c3da854dc60145d170008a2a09ab25027.1624013456.git.esben@geanix.com>
In-Reply-To: <d9200a5023973fbe372a2d51dc4e500400450ecd.1624013456.git.esben@geanix.com>
References: <d9200a5023973fbe372a2d51dc4e500400450ecd.1624013456.git.esben@geanix.com>
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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>
---
 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 cc482ee36501..9a13953ea70f 100644
--- a/drivers/net/ethernet/xilinx/ll_temac_main.c
+++ b/drivers/net/ethernet/xilinx/ll_temac_main.c
@@ -942,6 +942,11 @@ temac_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 	wmb();
 	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;
 }
 
-- 
2.32.0