Re: powerpc, fs_enet: scanning PHY after Linux is up

[Grant Likely <grant.likely@secretlab.ca>]

On Wed, Oct 6, 2010 at 7:50 AM, Holger brunck <holger.brunck@keymile.com> wrote:
> Hello Heiko,
>
> On 10/06/2010 11:53 AM, Heiko Schocher wrote:
>>>> So, the question is, is there a possibility to solve this problem?
>>>>
>>>> If there is no standard option, what would be with adding a
>>>> "scan_phy" file in
>>>>
>>>> /proc/device-tree/soc\@f0000000/cpm\@119c0/mdio\@10d40
>>>> (or better destination?)
>>>>
>>>> which with we could rescan a PHY with
>>>> "echo addr > /proc/device-tree/soc\@f0000000/cpm\@119c0/mdio\@10d40/scan_phy"
>>>> (so there is no need for using of_find_node_by_path(), as we should
>>>>  have the associated device node here, and can step through the child
>>>>  nodes with "for_each_child_of_node(np, child)" and check if reg == addr)
>>>>
>>>> or shouldn;t be at least, if the phy couldn;t be found when opening
>>>> the port, retrigger a scanning, if the phy now is accessible?
>>>
>>> One option would be to still register a phy_device for each phy
>>> described in the device tree, but defer binding a driver to each phy
>>> that doesn't respond.  Then at of_phy_find_device() time, if it
>>
>> Maybe I din;t get the trick, but the problem is, that
>> you can;t register a phy_device in drivers/of/of_mdio.c
>> of_mdiobus_register(), if the phy didn;t respond with the
>> phy_id ... and of_phy_find_device() is not (yet) used in fs_enet
>>
>>> matches with a phy_device that isn't bound to a driver yet, then
>>> re-trigger the binding operation.  At which point the phy id can be
>>> probed and the correct driver can be chosen.  If binding succeeds,
>>> then return the phy_device handle.  If not, then fail as it currently
>>> does.
>>
>> Wouldn;t it be good, just if we need a PHY (on calling fs_enet_open)
>> to look if there is one?
>>
>> Something like that (not tested):
>>
>> in drivers/net/fs_enet/fs_enet-main.c in fs_init_phy()
>> called from fs_enet_open():
>>
>> Do first:
>> phydev =  of_phy_find_device(fep->fpi->phy_node);
>>
>> Look if there is a driver (phy_dev->drv == NULL ?)
>>
>> If not, call new function
>> of_mdiobus_register_phy(mii_bus, fep->fpi->phy_node)
>> see below patch for it.
>>
>> If this succeeds, all is OK, and we can use this phy,
>> else ethernet not work.
>>
>> !!just no idea, how to get mii_bus pointer ...
>>
>
> in my understanding it should be posssible to get this pointer via the parent of
> the device_node you got via the private data of the fs_enet:
> fep->fpi->phy_node->parent should point you to the device_node for the mdio_bus.

Yes, this will give you the mdio bus node pointer.

> In the next step you should be able to get the pointer of of_device for the
> mdio_bus:
> ofdevice* ofdev = to_of_device(fep->fpi->phy_node->parent);

of_device is just an alias for platform_device now, and not all mdio
busses will be instantiated by a platform device.  This method won't
always work.  What is really needed is the pointer to the mii_bus
structure.  That can be obtained by looping over the members of the
mdio_bus_class and comparing the mii_bus->device.parent->of_node to
the parent node from above.

g.