netdev - Re: [PATCH] mdio_bus: Fix MDIO bus scanning in __mdiobus

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Message-ID: <5722C2A9.7090308@denx.de>
Date:	Fri, 29 Apr 2016 04:10:49 +0200
From:	Marek Vasut <marex@...x.de>
To:	Florian Fainelli <f.fainelli@...il.com>, netdev@...r.kernel.org
CC:	Arnd Bergmann <arnd@...db.de>,
	"David S . Miller" <davem@...emloft.net>,
	Dinh Nguyen <dinguyen@...nsource.altera.com>,
	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	Andrew Lunn <andrew@...n.ch>
Subject: Re: [PATCH] mdio_bus: Fix MDIO bus scanning in __mdiobus_register()

On 04/29/2016 03:49 AM, Florian Fainelli wrote:
> Le 28/04/2016 18:09, Marek Vasut a écrit :
>> Since commit b74766a0a0feeef5c779709cc5d109451c0d5b17 in linux-next,
>> ( phylib: don't return NULL from get_phy_device() ), phy_get_device()
>> will return ERR_PTR(-ENODEV) instead of NULL if the PHY device ID is
>> all ones.
>>
>> This causes problem with stmmac driver and likely some other drivers
>> which call mdiobus_register(). I triggered this bug on SoCFPGA MCVEVK
>> board with linux-next 20160427 and 20160428. In case of the stmmac, if
>> there is no PHY node specified in the DT for the stmmac block, the stmmac
>> driver ( drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c function
>> stmmac_mdio_register() ) will call mdiobus_register() , which will
>> register the MDIO bus and probe for the PHY.
>>
>> The mdiobus_register() resp. __mdiobus_register() iterates over all of
>> the addresses on the MDIO bus and calls mdiobus_scan() for each of them,
>> which invokes get_phy_device(). Before the aforementioned patch, the
>> mdiobus_scan() would return NULL if no PHY was found on a given address
>> and mdiobus_register() would continue and try the next PHY address. Now,
>> mdiobus_scan() returns ERR_PTR(-ENODEV), which is caught by the
>> 'if (IS_ERR(phydev))' condition and the loop exits immediatelly if the
>> PHY address does not contain PHY.
>>
>> Repair this by explicitly checking for the ERR_PTR(-ENODEV) and if this
>> error comes around, continue with the next PHY address.
>>
>> Signed-off-by: Marek Vasut <marex@...x.de>
>> Cc: Arnd Bergmann <arnd@...db.de>
>> Cc: David S. Miller <davem@...emloft.net>
>> Cc: Dinh Nguyen <dinguyen@...nsource.altera.com>
>> Cc: Florian Fainelli <f.fainelli@...il.com>
>> Cc: Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
> 
> Acked-by: Florian Fainelli <f.fainelli@...il.com>
> 
> I had an exact same patch posted yesterday but not formally like you
> did, thanks!

Ah, my google-fu must be weak tonight. Thanks!

>> ---
>>  drivers/net/phy/mdio_bus.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> NOTE: I don't quite like this explicit check , but I don't have better idea now.
>>
>> diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
>> index 499003ee..388f992 100644
>> --- a/drivers/net/phy/mdio_bus.c
>> +++ b/drivers/net/phy/mdio_bus.c
>> @@ -333,7 +333,7 @@ int __mdiobus_register(struct mii_bus *bus, struct module *owner)
>>  			struct phy_device *phydev;
>>  
>>  			phydev = mdiobus_scan(bus, i);
>> -			if (IS_ERR(phydev)) {
>> +			if (IS_ERR(phydev) && (PTR_ERR(phydev) != -ENODEV)) {
>>  				err = PTR_ERR(phydev);
>>  				goto error;
>>  			}
>>
> 
> 


-- 
Best regards,
Marek Vasut