net: stmmac: fix TSO and TBS feature enabling during driver open

TSO and TBS cannot co-exist and current implementation requires two
fixes:

 1) stmmac_open() does not need to call stmmac_enable_tbs() because
    the MAC is reset in stmmac_init_dma_engine() anyway.
 2) Inside stmmac_hw_setup(), we should call stmmac_enable_tso() for
    TX Q that is _not_ configured for TBS.

Fixes: 579a25a8 ("net: stmmac: Initial support for TBS")
Signed-off-by: Ong Boon Leong <boon.leong.ong@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -2757,9 +2757,16 @@ static int stmmac_hw_setup(struct net_device *dev, bool init_ptp)
 
 	/* Enable TSO */
 	if (priv->tso) {
-		for (chan = 0; chan < tx_cnt; chan++)
+		for (chan = 0; chan < tx_cnt; chan++) {
+			struct stmmac_tx_queue *tx_q = &priv->tx_queue[chan];
+
+			/* TSO and TBS cannot co-exist */
+			if (tx_q->tbs & STMMAC_TBS_AVAIL)
+				continue;
+
 			stmmac_enable_tso(priv, priv->ioaddr, 1, chan);
 		}
+	}
 
 	/* Enable Split Header */
 	if (priv->sph && priv->hw->rx_csum) {
@@ -2850,9 +2857,8 @@ static int stmmac_open(struct net_device *dev)
 		struct stmmac_tx_queue *tx_q = &priv->tx_queue[chan];
 		int tbs_en = priv->plat->tx_queues_cfg[chan].tbs_en;
 
+		/* Setup per-TXQ tbs flag before TX descriptor alloc */
 		tx_q->tbs |= tbs_en ? STMMAC_TBS_AVAIL : 0;
-		if (stmmac_enable_tbs(priv, priv->ioaddr, tbs_en, chan))
-			tx_q->tbs &= ~STMMAC_TBS_AVAIL;
 	}
 
 	ret = alloc_dma_desc_resources(priv);