net: stmmac: dwmac4: fix flow control issue

[ Upstream commit ee326fd01e79dfa42014d55931260b68b9fa3273 ]

Current dwmac4_flow_ctrl will not clear
GMAC_RX_FLOW_CTRL_RFE/GMAC_RX_FLOW_CTRL_RFE bits,
so MAC hw will keep flow control on although expecting
flow control off by ethtool. Add codes to fix it.

Fixes: 477286b53f55 ("stmmac: add GMAC4 core support")
Signed-off-by: Biao Huang <biao.huang@mediatek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c

@@ -475,8 +475,9 @@ static void dwmac4_flow_ctrl(struct mac_device_info *hw, unsigned int duplex,
 	if (fc & FLOW_RX) {
 		pr_debug("\tReceive Flow-Control ON\n");
 		flow |= GMAC_RX_FLOW_CTRL_RFE;
-		writel(flow, ioaddr + GMAC_RX_FLOW_CTRL);
 	}
+	writel(flow, ioaddr + GMAC_RX_FLOW_CTRL);
+
 	if (fc & FLOW_TX) {
 		pr_debug("\tTransmit Flow-Control ON\n");
 
@@ -484,7 +485,7 @@ static void dwmac4_flow_ctrl(struct mac_device_info *hw, unsigned int duplex,
 			pr_debug("\tduplex mode: PAUSE %d\n", pause_time);
 
 		for (queue = 0; queue < tx_cnt; queue++) {
-			flow |= GMAC_TX_FLOW_CTRL_TFE;
+			flow = GMAC_TX_FLOW_CTRL_TFE;
 
 			if (duplex)
 				flow |=
@@ -492,6 +493,9 @@ static void dwmac4_flow_ctrl(struct mac_device_info *hw, unsigned int duplex,
 
 			writel(flow, ioaddr + GMAC_QX_TX_FLOW_CTRL(queue));
 		}
+	} else {
+		for (queue = 0; queue < tx_cnt; queue++)
+			writel(0, ioaddr + GMAC_QX_TX_FLOW_CTRL(queue));
 	}
 }