netdev - Re: [PATCH net-next v2 1/3] net: phy: marvell10g: add mdix control

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Date:   Tue, 3 Mar 2020 18:03:16 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Russell King <rmk+kernel@...linux.org.uk>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Antoine Tenart <antoine.tenart@...tlin.com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v2 1/3] net: phy: marvell10g: add mdix control

> +static int mv3310_reset(struct phy_device *phydev, u32 unit)
> +{
> +	int retries, val, err;
> +
> +	err = phy_modify_mmd(phydev, MDIO_MMD_PCS, unit + MDIO_CTRL1,
> +			     MDIO_CTRL1_RESET, MDIO_CTRL1_RESET);
> +	if (err < 0)
> +		return err;
> +
> +	retries = 20;
> +	do {
> +		msleep(5);
> +		val = phy_read_mmd(phydev, MDIO_MMD_PCS, unit + MDIO_CTRL1);
> +		if (val < 0)
> +			return val;
> +	} while (val & MDIO_CTRL1_RESET && --retries);
> +
> +	return val & MDIO_CTRL1_RESET ? -ETIMEDOUT : 0;

Hi Russell

I've often seen people get this sort of polling loop wrong. So i
generally point people towards include/linux/iopoll.h.

I wonder if it would be helpful to add phy_read_mmd_poll_timeout()
and maybe phy_read_poll_timeout() to phy-core.c?

Just an idea, not a blocker for the patch.

     Andrew