Subject: Re: [PATCH v2 1/2] net: phy: Set the driver when registering an MDIO bus device

From: Florian Fainelli <[email-masked]>
Date: Mon, 04 Aug 2014 21:01:06 -0700

On 08/04/14 20:22, Shawn Guo wrote:
> On Mon, Aug 04, 2014 at 11:55:22PM -0300, Fabio Estevam wrote:
>> Hi Ezequiel,
>>
>> On Wed, Jul 23, 2014 at 4:47 PM, Ezequiel Garcia
>> <[email-masked]> wrote:
>>> mdiobus_register() registers a device which is already bound to a driver.
>>> Hence, the driver pointer should be set properly in order to track down
>>> the driver associated to the MDIO bus.
>>>
>>> This will be used to allow ethernet driver to pin down a MDIO bus driver,
>>> preventing it from being unloaded while the PHY device is running.
>>>
>>> Reviewed-by: Florian Fainelli <[email-masked]>
>>> Tested-by: Florian Fainelli <[email-masked]>
>>> Signed-off-by: Ezequiel Garcia <[email-masked]>
>>> ---
>>>   drivers/net/phy/mdio_bus.c | 1 +
>>>   1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
>>> index 4eaadcf..203651e 100644
>>> --- a/drivers/net/phy/mdio_bus.c
>>> +++ b/drivers/net/phy/mdio_bus.c
>>> @@ -255,6 +255,7 @@ int mdiobus_register(struct mii_bus *bus)
>>>
>>>          bus->dev.parent = bus->parent;
>>>          bus->dev.class = &mdio_bus_class;
>>> +       bus->dev.driver = bus->parent->driver;
>>>          bus->dev.groups = NULL;
>>>          dev_set_name(&bus->dev, "%s", bus->id);
>>
>> This patches causes the following regression in 3.16 (tested on mx5/mx6):
>
> The change will trigger a device_suspend() call on mii_bus device with
> the pm suspend/resume callbacks being fec driver ones, since
> bus->parent->driver points to fec driver.
>
> So net result is fec_suspend() will be called twice during suspend, once
> in mii_bus device context and the other in fec device context.  In fec
> context, it works just fine.  And the issue we're seeing is from mii_bus
> device context, where the driver_data of the device is invalid.
>
> I do not think fec_suspend() should be called in mii_bus device context.

Right, that does not sound like a good thing to do. Does it work if you 
call pm_suspend_ignore_children() either in the FEC driver or in 
mdiobus_register()?

I am not exactly sure what the best solution looks like at this point

> Shawn