net: stmmac: xgmac: Disable Flow Control when 1 or more queues are in AV

When in AVB mode we need to disable flow control to prevent MAC from
pausing in TX side.

Fixes: ec6ea8e3 ("net: stmmac: Add CBS support in XGMAC2")
Signed-off-by: Jose Abreu <Jose.Abreu@synopsys.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c

@@ -470,6 +470,7 @@ static void dwxgmac2_enable_tso(void __iomem *ioaddr, bool en, u32 chan)
 static void dwxgmac2_qmode(void __iomem *ioaddr, u32 channel, u8 qmode)
 {
 	u32 value = readl(ioaddr + XGMAC_MTL_TXQ_OPMODE(channel));
+	u32 flow = readl(ioaddr + XGMAC_RX_FLOW_CTRL);
 
 	value &= ~XGMAC_TXQEN;
 	if (qmode != MTL_QUEUE_AVB) {
@@ -477,6 +478,7 @@ static void dwxgmac2_qmode(void __iomem *ioaddr, u32 channel, u8 qmode)
 		writel(0, ioaddr + XGMAC_MTL_TCx_ETS_CONTROL(channel));
 	} else {
 		value |= 0x1 << XGMAC_TXQEN_SHIFT;
+		writel(flow & (~XGMAC_RFE), ioaddr + XGMAC_RX_FLOW_CTRL);
 	}
 
 	writel(value, ioaddr +  XGMAC_MTL_TXQ_OPMODE(channel));