net: stmmac: provide stmmac_eee_tx_busy()

Extract the code which checks whether there's still work to do on any
of the stmmac transmit queues. This will allow us to combine
stmmac_enable_eee_mode() with stmmac_try_to_start_sw_lpi() in the
next patch.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/E1tXItR-000MBO-GF@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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

@@ -400,13 +400,7 @@ static void stmmac_enable_hw_lpi_timer(struct stmmac_priv *priv)
 	stmmac_set_eee_lpi_timer(priv, priv->hw, priv->tx_lpi_timer);
 }
 
-/**
- * stmmac_enable_eee_mode - check and enter in LPI mode
- * @priv: driver private structure
- * Description: this function is to verify and enter in LPI mode in case of
- * EEE.
- */
-static int stmmac_enable_eee_mode(struct stmmac_priv *priv)
+static bool stmmac_eee_tx_busy(struct stmmac_priv *priv)
 {
 	u32 tx_cnt = priv->plat->tx_queues_to_use;
 	u32 queue;
@@ -416,9 +410,23 @@ static int stmmac_enable_eee_mode(struct stmmac_priv *priv)
 		struct stmmac_tx_queue *tx_q = &priv->dma_conf.tx_queue[queue];
 
 		if (tx_q->dirty_tx != tx_q->cur_tx)
-			return -EBUSY; /* still unfinished work */
+			return true; /* still unfinished work */
 	}
 
+	return false;
+}
+
+/**
+ * stmmac_enable_eee_mode - check and enter in LPI mode
+ * @priv: driver private structure
+ * Description: this function is to verify and enter in LPI mode in case of
+ * EEE.
+ */
+static int stmmac_enable_eee_mode(struct stmmac_priv *priv)
+{
+	if (stmmac_eee_tx_busy(priv))
+		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,