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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Jiangfeng Xiao <xiaojiangfeng@huawei.com>,
        "David S. Miller" <davem@davemloft.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.9 21/83] net: hisilicon: fix hip04-xmit never return TX_BUSY
Date:   Wed,  4 Sep 2019 19:53:13 +0200
Message-Id: <20190904175305.739945720@linuxfoundation.org>
In-Reply-To: <20190904175303.488266791@linuxfoundation.org>
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[ Upstream commit f2243b82785942be519016067ee6c55a063bbfe2 ]

TX_DESC_NUM is 256, in tx_count, the maximum value of
mod(TX_DESC_NUM - 1) is 254, the variable "count" in
the hip04_mac_start_xmit function is never equal to
(TX_DESC_NUM - 1), so hip04_mac_start_xmit never
return NETDEV_TX_BUSY.

tx_count is modified to mod(TX_DESC_NUM) so that
the maximum value of tx_count can reach
(TX_DESC_NUM - 1), then hip04_mac_start_xmit can reurn
NETDEV_TX_BUSY.

Signed-off-by: Jiangfeng Xiao <xiaojiangfeng@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/ethernet/hisilicon/hip04_eth.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/hisilicon/hip04_eth.c b/drivers/net/ethernet/hisilicon/hip04_eth.c
index 1fabbbd4544e7..c7e0b246cfdca 100644
--- a/drivers/net/ethernet/hisilicon/hip04_eth.c
+++ b/drivers/net/ethernet/hisilicon/hip04_eth.c
@@ -185,7 +185,7 @@ struct hip04_priv {
 
 static inline unsigned int tx_count(unsigned int head, unsigned int tail)
 {
-	return (head - tail) % (TX_DESC_NUM - 1);
+	return (head - tail) % TX_DESC_NUM;
 }
 
 static void hip04_config_port(struct net_device *ndev, u32 speed, u32 duplex)
-- 
2.20.1