net: stmmac: reduce unnecessary wakeups from eee sw timer

Currently, on EEE capable platforms, if EEE SW timer is used, the SW
timer cause 1 wakeup/s even if the TX has successfully entered EEE.
Remove this unnecessary wakeup by only calling mod_timer() if we
haven't successfully entered EEE.
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -402,7 +402,7 @@ static void stmmac_lpi_entry_timer_config(struct stmmac_priv *priv, bool en)
  * Description: this function is to verify and enter in LPI mode in case of
  * EEE.
  */
-static void stmmac_enable_eee_mode(struct stmmac_priv *priv)
+static int stmmac_enable_eee_mode(struct stmmac_priv *priv)
 {
 	u32 tx_cnt = priv->plat->tx_queues_to_use;
 	u32 queue;
@@ -412,13 +412,14 @@ static void stmmac_enable_eee_mode(struct stmmac_priv *priv)
 		struct stmmac_tx_queue *tx_q = &priv->tx_queue[queue];
 
 		if (tx_q->dirty_tx != tx_q->cur_tx)
-			return; /* still unfinished work */
+			return -EBUSY; /* still unfinished work */
 	}
 
 	/* Check and enter in LPI mode */
 	if (!priv->tx_path_in_lpi_mode)
 		stmmac_set_eee_mode(priv, priv->hw,
 				priv->plat->en_tx_lpi_clockgating);
+	return 0;
 }
 
 /**
@@ -450,8 +451,8 @@ static void stmmac_eee_ctrl_timer(struct timer_list *t)
 {
 	struct stmmac_priv *priv = from_timer(priv, t, eee_ctrl_timer);
 
-	stmmac_enable_eee_mode(priv);
-	mod_timer(&priv->eee_ctrl_timer, STMMAC_LPI_T(priv->tx_lpi_timer));
+	if (stmmac_enable_eee_mode(priv))
+		mod_timer(&priv->eee_ctrl_timer, STMMAC_LPI_T(priv->tx_lpi_timer));
 }
 
 /**
@@ -2647,8 +2648,8 @@ static int stmmac_tx_clean(struct stmmac_priv *priv, int budget, u32 queue)
 
 	if (priv->eee_enabled && !priv->tx_path_in_lpi_mode &&
 	    priv->eee_sw_timer_en) {
-		stmmac_enable_eee_mode(priv);
-		mod_timer(&priv->eee_ctrl_timer, STMMAC_LPI_T(priv->tx_lpi_timer));
+		if (stmmac_enable_eee_mode(priv))
+			mod_timer(&priv->eee_ctrl_timer, STMMAC_LPI_T(priv->tx_lpi_timer));
 	}
 
 	/* We still have pending packets, let's call for a new scheduling */