netdev - Re: [Linux-stm32] [PATCH net-next 3/5] net: stmmac: avoid PHY speed change when configuring MTU

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Message-ID: <f9c7b80b-b750-4eaa-b528-7028e8d8295a@foss.st.com>
Date: Thu, 16 Oct 2025 09:44:02 +0200
From: Gatien CHEVALLIER <gatien.chevallier@...s.st.com>
To: "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
        Andrew Lunn
	<andrew@...n.ch>, Heiner Kallweit <hkallweit1@...il.com>
CC: <netdev@...r.kernel.org>, <linux-stm32@...md-mailman.stormreply.com>,
        Andrew Lunn <andrew+netdev@...n.ch>,
        Eric Dumazet <edumazet@...gle.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Jakub Kicinski
	<kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
        "David S. Miller"
	<davem@...emloft.net>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [Linux-stm32] [PATCH net-next 3/5] net: stmmac: avoid PHY speed
 change when configuring MTU



On 10/15/25 18:10, Russell King (Oracle) wrote:
> 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>

Reviewed-by: Gatien Chevallier <gatien.chevallier@...s.st.com>

> ---
>   .../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);