netdev - [PATCH net-next 3/5] net: stmmac: avoid PHY speed change when configuring MTU

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Message-Id: <E1v945T-0000000AmeV-2BvU@rmk-PC.armlinux.org.uk>
Date: Wed, 15 Oct 2025 17:10:51 +0100
From: "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>
To: Andrew Lunn <andrew@...n.ch>,
	Heiner Kallweit <hkallweit1@...il.com>
Cc: Alexandre Torgue <alexandre.torgue@...s.st.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	linux-arm-kernel@...ts.infradead.org,
	linux-stm32@...md-mailman.stormreply.com,
	Maxime Coquelin <mcoquelin.stm32@...il.com>,
	netdev@...r.kernel.org,
	Paolo Abeni <pabeni@...hat.com>
Subject: [PATCH net-next 3/5] net: stmmac: avoid PHY speed change when
 configuring MTU

There is no need to do the speed-down, speed-up dance when changing
the MTU as there is little power saving that can be gained from such
a brief interval between these, and the autonegotiation they cause
takes much longer.

Move the calls to phylink_speed_up() and phylink_speed_down() into
stmmac_open() and stmmac_release() respectively, reducing the work
done in the __-variants of these functions.

Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
---
 .../net/ethernet/stmicro/stmmac/stmmac_main.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 3728afa701c6..500cfd19e6b5 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -3963,8 +3963,6 @@ static int __stmmac_open(struct net_device *dev,
 	stmmac_init_coalesce(priv);
 
 	phylink_start(priv->phylink);
-	/* We may have called phylink_speed_down before */
-	phylink_speed_up(priv->phylink);
 
 	ret = stmmac_request_irq(dev);
 	if (ret)
@@ -4015,6 +4013,9 @@ static int stmmac_open(struct net_device *dev)
 
 	kfree(dma_conf);
 
+	/* We may have called phylink_speed_down before */
+	phylink_speed_up(priv->phylink);
+
 	return ret;
 
 err_disconnect_phy:
@@ -4032,13 +4033,6 @@ static void __stmmac_release(struct net_device *dev)
 	struct stmmac_priv *priv = netdev_priv(dev);
 	u32 chan;
 
-	/* If the PHY or MAC has WoL enabled, then the PHY will not be
-	 * suspended when phylink_stop() is called below. Set the PHY
-	 * to its slowest speed to save power.
-	 */
-	if (device_may_wakeup(priv->device))
-		phylink_speed_down(priv->phylink, false);
-
 	/* Stop and disconnect the PHY */
 	phylink_stop(priv->phylink);
 
@@ -4078,6 +4072,13 @@ static int stmmac_release(struct net_device *dev)
 {
 	struct stmmac_priv *priv = netdev_priv(dev);
 
+	/* If the PHY or MAC has WoL enabled, then the PHY will not be
+	 * suspended when phylink_stop() is called below. Set the PHY
+	 * to its slowest speed to save power.
+	 */
+	if (device_may_wakeup(priv->device))
+		phylink_speed_down(priv->phylink, false);
+
 	__stmmac_release(dev);
 
 	phylink_disconnect_phy(priv->phylink);
-- 
2.47.3