David Daney wrote:
> I wonder if *fpga is really a good name for this. It is a general
> purpose multiplexer with a memory mapped control register. I would call
> it something like mdio-mux-mmioreg.
At one point, I thought of using mdio-mux-bitbang, but -mmioreg is better.
Thanks.
>> +- mdio-mux-device : phandle, points to the FPGA (or similar) node. This
>> + must be a memory-mapped device with 8-bit registers.
>
> You shouldn't need this. Just make the multiplexer a child of FPGA node
> to indicate where it lives.
The problem is that we don't normally consider the FPGA node to be a bus,
so its child nodes won't get probed. That's why I have this:
compatible = "mdio-mux-fpga", "mdio-mux";
^^^^^^^^
This allows me to have multiple mdio-mux parent nodes (which I do, since I
have multiple mdio bus muxes), and they all get registered and probed
properly because I also do this:
static const struct of_device_id of_device_ids[] __devinitconst = {
{
.compatible = "simple-bus"
},
{
.compatible = "fsl,srio",
},
...
{
.compatible = "mdio-mux",
},
{}
};
The .compatible = "mdio-mux" is what causes all of the mdio-mux nodes to
be registered. Therefore, it's simpler if all the mdio-mux nodes are root
nodes.
>> +
>> +- mdio-mux-register : integer, contains the offset of the register that
>> + controls the bus multiplexer.
>
> This should just be the normal "reg" properly
Ok.
>> +- mdio-mux-mask : integer, contains an 8-bit mask that specifies which
>> + bits in the register control the actual bus multiplexer. The
>> + 'reg' property of each child mdio-mux node must be constrained by
>> + this mask.
>> +
>
> "reg-mask" ??
Ok.
>
> Do you need a shift too?
The 'reg' property of the mdio bus child nodes should take the shift into
account. That's why, in the example, I have mask=0x6 and reg=0 or reg=2.
There's even code in the driver to make sure that the 'reg' values are
constrained to the mask.
--
Timur Tabi
Linux kernel developer at Freescale
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