net: stmmac: perserve TX and RX coalesce value during XDP setup

When XDP program is loaded, it is desirable that the previous TX and RX
coalesce values are not re-inited to its default value. This prevents
unnecessary re-configurig the coalesce values that were working fine
before.

Fixes: ac746c85 ("net: stmmac: enhance XDP ZC driver level switching performance")
Signed-off-by: Ong Boon Leong <boon.leong.ong@intel.com>
Tested-by: Kurt Kanzenbach <kurt@linutronix.de>
Link: https://lore.kernel.org/r/20211124114019.3949125-1-boon.leong.ong@intel.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

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

@@ -6519,6 +6519,9 @@ int stmmac_xdp_open(struct net_device *dev)
 		tx_q->tx_tail_addr = tx_q->dma_tx_phy;
 		stmmac_set_tx_tail_ptr(priv, priv->ioaddr,
 				       tx_q->tx_tail_addr, chan);
+
+		hrtimer_init(&tx_q->txtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+		tx_q->txtimer.function = stmmac_tx_timer;
 	}
 
 	/* Enable the MAC Rx/Tx */
@@ -6527,8 +6530,6 @@ int stmmac_xdp_open(struct net_device *dev)
 	/* Start Rx & Tx DMA Channels */
 	stmmac_start_all_dma(priv);
 
-	stmmac_init_coalesce(priv);
-
 	ret = stmmac_request_irq(dev);
 	if (ret)
 		goto irq_error;