Re: [PATCH net-next 4/8] net: dsa: mv88e6xxx: do not increment bus refcount

Vivien Didelot
2016-06-10T19:59:30Z

Hi,

Andrew Lunn <andrew@lunn.ch> writes:

> On Wed, Jun 08, 2016 at 08:44:52PM -0400, Vivien Didelot wrote:
>> The MDIO device probe and remove functions are respectively incrementing
>> and decrementing the bus refcount themselves. Since these bus level
>> actions are out of the device scope, remove them.
>
> I agree with the patch. But have you checked the mdio layer is doing
> the right thing? If not, we should fix that first.

So I added some printing after incrementing/decrementing the refcount in
get_device/put_device to track &ps->bus->dev, which name is "0.1".

Regardless having this patch or not, the refcount of the 0.1 mii_bus
device is 5 before loading the mv88e6xxx module on vf610-zii-dev-rev-b.

Below is a portion of dmesg:

[ 8.921647] get_device: 400d1000.etherne refcount: 4
[ 8.926225] get_device: 0.1 refcount: 2
[ 8.929561] get_device: mdio-mux refcount: 5
[ 8.934076] get_device: 0.1 refcount: 3
[ 8.937446] get_device: 0.1 refcount: 4
[ 8.940792] put_device: 0.1 refcount: 3
[ 8.944181] libphy: mdio_mux: probed
[ 8.947885] mdio_bus 0.1:00: mdio_device_register
[ 8.952649] get_device: 0.1:00 refcount: 2
[ 8.956283] get_device: 0.1 refcount: 4
[ 8.959838] get_device: 0.1:00 refcount: 3
[ 8.963991] get_device: 0.1:00 refcount: 4
[ 8.967598] put_device: 0.1:00 refcount: 3
[ 8.971298] get_device: 0.2 refcount: 2
[ 8.974687] get_device: mdio-mux refcount: 7

So it seems like of_ is managing the bus refcount on events such as a
new child node (0.1:00).

Thanks,

Vivien