netdev - Re: [PATCH net-next 1/1] net: phy: fix invalid phy id when probe using C22

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Date:   Wed, 17 Mar 2021 09:15:03 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Wong Vee Khee <vee.khee.wong@...el.com>,
        Andrew Lunn <andrew@...n.ch>,
        Russell King <linux@...linux.org.uk>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, Voon Weifeng <voon.weifeng@...el.com>,
        Ong Boon Leong <boon.leong.ong@...el.com>
Subject: Re: [PATCH net-next 1/1] net: phy: fix invalid phy id when probe
 using C22

On 16.03.2021 09:57, Wong Vee Khee wrote:
> When using Clause-22 to probe for PHY devices such as the Marvell
> 88E2110, PHY ID with value 0 is read from the MII PHYID registers
> which caused the PHY framework failed to attach the Marvell PHY
> driver.
> 

The issue occurs with a MAC driver that sets MDIO bus capability
flag MDIOBUS_C22_C45, like stmmac? Or what is the affected MAC
driver?

And if you state it's a fix, a Fixes tag would be needed.

> Fixed this by adding a check of PHY ID equals to all zeroes.
> 
> Cc: stable@...r.kernel.org
> Reviewed-by: Voon Weifeng <voon.weifeng@...el.com>
> Signed-off-by: Wong Vee Khee <vee.khee.wong@...el.com>
> ---
>  drivers/net/phy/phy_device.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> index a009d1769b08..f1afc00fcba2 100644
> --- a/drivers/net/phy/phy_device.c
> +++ b/drivers/net/phy/phy_device.c
> @@ -820,8 +820,8 @@ static int get_phy_c22_id(struct mii_bus *bus, int addr, u32 *phy_id)
>  
>  	*phy_id |= phy_reg;
>  
> -	/* If the phy_id is mostly Fs, there is no device there */
> -	if ((*phy_id & 0x1fffffff) == 0x1fffffff)
> +	/* If the phy_id is mostly Fs or all zeroes, there is no device there */
> +	if (((*phy_id & 0x1fffffff) == 0x1fffffff) || (*phy_id == 0))
>  		return -ENODEV;
>  
>  	return 0;
>