linux-kernel - [PATCH net-next 1/6] net: stmmac: Prevent divide-by-zero

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Message-Id: <04b4d5cff05dc751029ff02e2dadfdb206bf3d11.1568126224.git.joabreu@synopsys.com>
Date:   Tue, 10 Sep 2019 16:41:22 +0200
From:   Jose Abreu <Jose.Abreu@...opsys.com>
To:     netdev@...r.kernel.org
Cc:     Joao Pinto <Joao.Pinto@...opsys.com>,
        Jose Abreu <Jose.Abreu@...opsys.com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        "David S. Miller" <davem@...emloft.net>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH net-next 1/6] net: stmmac: Prevent divide-by-zero

When RX Coalesce settings are set to all zero (which is a valid setting)
we will currently get a divide-by-zero error. Fix it.

Signed-off-by: Jose Abreu <joabreu@...opsys.com>

---
Cc: Giuseppe Cavallaro <peppe.cavallaro@...com>
Cc: Alexandre Torgue <alexandre.torgue@...com>
Cc: Jose Abreu <joabreu@...opsys.com>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Maxime Coquelin <mcoquelin.stm32@...il.com>
Cc: netdev@...r.kernel.org
Cc: linux-stm32@...md-mailman.stormreply.com
Cc: linux-arm-kernel@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 686b82068142..6e44013b20cc 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -3418,7 +3418,9 @@ static inline void stmmac_rx_refill(struct stmmac_priv *priv, u32 queue)
 		stmmac_refill_desc3(priv, rx_q, p);
 
 		rx_q->rx_count_frames++;
-		rx_q->rx_count_frames %= priv->rx_coal_frames;
+		rx_q->rx_count_frames += priv->rx_coal_frames;
+		if (rx_q->rx_count_frames > priv->rx_coal_frames)
+			rx_q->rx_count_frames = 0;
 		use_rx_wd = priv->use_riwt && rx_q->rx_count_frames;
 
 		dma_wmb();
-- 
2.7.4