netdev - Re: [PATCH net-next] net: stmmac: dwc-qos: calibrate tegra with mdio bus idle

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Message-ID: <20250422164230.5ffb90d3@fedora.home>
Date: Tue, 22 Apr 2025 16:42:30 +0200
From: Maxime Chevallier <maxime.chevallier@...tlin.com>
To: "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>
Cc: Andrew Lunn <andrew@...n.ch>, 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>, Jon Hunter
 <jonathanh@...dia.com>, 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>, Thierry Reding <treding@...dia.com>
Subject: Re: [PATCH net-next] net: stmmac: dwc-qos: calibrate tegra with
 mdio bus idle

Hello Russell,

On Tue, 22 Apr 2025 15:24:55 +0100
"Russell King (Oracle)" <rmk+kernel@...linux.org.uk> wrote:

> Thierry states that there are prerequists for Tegra's calibration
> that should be met before starting calibration - both the RGMII and
> MDIO interfaces should be idle.
> 
> This commit adds the necessary MII bus locking to ensure that the MDIO
> interface is idle during calibration.
> 
> Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>

[...]

> -static void tegra_eqos_fix_speed(void *priv, int speed, unsigned int mode)
> +static void tegra_eqos_fix_speed(void *bsp_priv, int speed, unsigned int mode)
>  {
> -	struct tegra_eqos *eqos = priv;
> +	struct tegra_eqos *eqos = bsp_priv;
>  	bool needs_calibration = false;
> +	struct stmmac_priv *priv;
>  	u32 value;
>  	int err;
>  
> @@ -158,6 +159,11 @@ static void tegra_eqos_fix_speed(void *priv, int speed, unsigned int mode)
>  	}
>  
>  	if (needs_calibration) {
> +		priv = netdev_priv(dev_get_drvdata(eqos->dev));
> +
> +		/* Calibration should be done with the MDIO bus idle */
> +		mutex_lock(&priv->mii->mdio_lock);

Can't priv->mii be NULL, if the PHY for that MAC is connected to
another MDIO bus for instance ?

Maxime