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

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Date:	Tue, 5 Aug 2014 07:43:32 -0300
From:	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
To:	Shawn Guo <shawn.guo@...escale.com>
Cc:	Florian Fainelli <f.fainelli@...il.com>,
	Fabio Estevam <festevam@...il.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Gregory Clement <gregory.clement@...e-electrons.com>,
	Marek Vašut <marex@...x.de>,
	Sascha Hauer <kernel@...gutronix.de>,
	Russell King <linux@....linux.org.uk>
Subject: Re: [PATCH v2 1/2] net: phy: Set the driver when registering an MDIO
 bus device

Hi Shawn,

On 05 Aug 12:41 PM, Shawn Guo wrote:
> On Mon, Aug 04, 2014 at 09:01:06PM -0700, Florian Fainelli wrote:
> > 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
> > >><ezequiel.garcia@...e-electrons.com> 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 <f.fainelli@...il.com>
> > >>>Tested-by: Florian Fainelli <f.fainelli@...il.com>
> > >>>Signed-off-by: Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
> > >>>---
> > >>>  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()?
> 
> No, it doesn't stop fec_suspend() being called from mii_bus device
> context.
> 
> > 
> > I am not exactly sure what the best solution looks like at this point
> 
> Let's see if Ezequiel has any idea, but otherwise we should probably
> revert the patch for 3.16 stable.
> 

Indeed, this commit should be reverted.

Sorry for the crap,
-- 
Ezequiel García, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com
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