netdev - [PATCH net 1/1] net: stmmac: Fix zero-division error when disabling tc cbs

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Message-Id: <20240912015541.363600-1-khai.wen.tan@linux.intel.com>
Date: Thu, 12 Sep 2024 09:55:41 +0800
From: KhaiWenTan <khai.wen.tan@...ux.intel.com>
To: Alexandre Torgue <alexandre.torgue@...s.st.com>,
	Jose Abreu <joabreu@...opsys.com>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Maxime Coquelin <mcoquelin.stm32@...il.com>,
	Simon Horman <horms@...nel.org>,
	Xiaolei Wang <xiaolei.wang@...driver.com>
Cc: netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-stm32@...md-mailman.stormreply.com,
	linux-arm-kernel@...ts.infradead.org,
	Choong Yong Liang <yong.liang.choong@...ux.intel.com>,
	Tan Khai Wen <khai.wen.tan@...el.com>
Subject: [PATCH net 1/1] net: stmmac: Fix zero-division error when disabling tc cbs

The commit b8c43360f6e4 ("net: stmmac: No need to calculate speed divider
when offload is disabled") allows the "port_transmit_rate_kbps" to be
set to a value of 0, which is then passed to the "div_s64" function when
tc-cbs is disabled. This leads to a zero-division error.

When tc-cbs is disabled, the idleslope, sendslope, and credit values the
credit values are not required to be configured. Therefore, adding a return
statement after setting the txQ mode to DCB when tc-cbs is disabled would
prevent a zero-division error.

Fixes: b8c43360f6e4 ("net: stmmac: No need to calculate speed divider when offload is disabled")
Cc: <stable@...r.kernel.org>
Co-developed-by: Choong Yong Liang <yong.liang.choong@...ux.intel.com>
Signed-off-by: Choong Yong Liang <yong.liang.choong@...ux.intel.com>
Signed-off-by: KhaiWenTan <khai.wen.tan@...ux.intel.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
index 996f2bcd07a2..2c3fd9c66d14 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
@@ -392,10 +392,10 @@ static int tc_setup_cbs(struct stmmac_priv *priv,
 	} else if (!qopt->enable) {
 		ret = stmmac_dma_qmode(priv, priv->ioaddr, queue,
 				       MTL_QUEUE_DCB);
-		if (ret)
-			return ret;
+		if (!ret)
+			priv->plat->tx_queues_cfg[queue].mode_to_use = MTL_QUEUE_DCB;
 
-		priv->plat->tx_queues_cfg[queue].mode_to_use = MTL_QUEUE_DCB;
+		return ret;
 	}
 
 	/* Final adjustments for HW */
-- 
2.25.1