netdev - Re: [PATCH RFC net-next 7/7] net: stmmac: explain the phylink_speed_down() call in stmmac

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Message-ID: <b612eaee-17f2-4cab-bc37-a1cb9560ffe1@lunn.ch>
Date: Mon, 28 Jul 2025 19:29:09 +0200
From: Andrew Lunn <andrew@...n.ch>
To: "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>
Cc: Heiner Kallweit <hkallweit1@...il.com>,
	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: Re: [PATCH RFC net-next 7/7] net: stmmac: explain the
 phylink_speed_down() call in stmmac_release()

On Mon, Jul 28, 2025 at 04:46:02PM +0100, Russell King (Oracle) wrote:
> The call to phylink_speed_down() looks odd on the face of it. Add a
> comment to explain why this call is there.
> 
> Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index f44f8b1b0efa..0da5c29b8cb0 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -4138,8 +4138,13 @@ static int 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);
> +

Is there a corresponding phylink_speed_up() somewhere else? Does that
need a similar comment?

	Andrew