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

[Wong, Vee Khee]

> -----Original Message-----
> From: Heiner Kallweit <hkallweit1@xxxxxxxxx>
> Sent: Wednesday, March 17, 2021 4:15 PM
> To: Wong, Vee Khee <vee.khee.wong@xxxxxxxxx>; Andrew Lunn
> <andrew@xxxxxxx>; Russell King <linux@xxxxxxxxxxxxxxx>; David S . Miller
> <davem@xxxxxxxxxxxxx>; Jakub Kicinski <kuba@xxxxxxxxxx>
> Cc: netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> stable@xxxxxxxxxxxxxxx; Voon Weifeng <voon.weifeng@xxxxxxxxx>; Ong,
> Boon Leong <boon.leong.ong@xxxxxxxxx>
> 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?
> 

Yes, you are right. This issue is seen when MarvellE2110 is used with
the STMMAC.

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

Noted. Will send a v2 and marked for net.

> > Fixed this by adding a check of PHY ID equals to all zeroes.
> >
> > Cc: stable@xxxxxxxxxxxxxxx
> > Reviewed-by: Voon Weifeng <voon.weifeng@xxxxxxxxx>
> > Signed-off-by: Wong Vee Khee <vee.khee.wong@xxxxxxxxx>
> > ---
> >  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;
> >