linux-kernel - Re: [PATCH net] net: phy: Avoid WARN_ON for PHY

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Message-ID: <4d2d6349-6910-3e73-e6c5-db9041bcfdb8@gmail.com>
Date:   Fri, 21 Oct 2022 10:38:10 +0200
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>,
        Andrew Lunn <andrew@...n.ch>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] net: phy: Avoid WARN_ON for PHY_NOLINK during
 resuming

On 21.10.2022 09:41, Kunihiko Hayashi wrote:
> When resuming from sleep, if there is a time lag from link-down to link-up
> due to auto-negotiation, the phy status has been still PHY_NOLINK, so
> WARN_ON dump occurs in mdio_bus_phy_resume(). For example, UniPhier AVE
> ethernet takes about a few seconds to link up after resuming.
> 
That autoneg takes some time is normal. If this would actually the root
cause then basically every driver should be affected. But it's not.

> To avoid this issue, should remove PHY_NOLINK the WARN_ON conditions.
> 
> Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
> ---
>  drivers/net/phy/phy_device.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> index 57849ac0384e..c647d027bb5d 100644
> --- a/drivers/net/phy/phy_device.c
> +++ b/drivers/net/phy/phy_device.c
> @@ -318,12 +318,12 @@ static __maybe_unused int mdio_bus_phy_resume(struct device *dev)
>  	phydev->suspended_by_mdio_bus = 0;
>  
>  	/* If we managed to get here with the PHY state machine in a state
> -	 * neither PHY_HALTED, PHY_READY nor PHY_UP, this is an indication
> -	 * that something went wrong and we should most likely be using
> -	 * MAC managed PM, but we are not.
> +	 * neither PHY_HALTED, PHY_READY, PHY_UP nor PHY_NOLINK, this is an
> +	 * indication that something went wrong and we should most likely
> +	 * be using MAC managed PM, but we are not.
>  	 */

Did you read the comment you're changing? ave_resume() calls phy_resume(),
so you should follow the advice in the comment.

>  	WARN_ON(phydev->state != PHY_HALTED && phydev->state != PHY_READY &&
> -		phydev->state != PHY_UP);
> +		phydev->state != PHY_UP && phydev->state != PHY_NOLINK);
>  
>  	ret = phy_init_hw(phydev);
>  	if (ret < 0)