Re: [PATCH v6 0/3] netdev/of/phy: MDIO bus multiplexer support.

On 05/18/2012 02:42 PM, Tabi Timur-B04825 wrote:

On Wed, May 2, 2012 at 8:16 PM, David Daney[off-list ref]  wrote:

quoted

From: David Daney<redacted>

This code has been working well for about six months on a couple of
different configurations (boards), so I thought it would be a good
time to send it out again, and I hope get it on the path towards
merging.

David,

I'm trying to implement this feature on our boards, which don't use
GPIOs but rather a memory-mapped FPGA.  I control the mux by setting
some bits in one of the FPGA registers.

You can either:

1) write a standard GPIO driver for the thing that controls the mux, and 
then use mdio-mux-gpio.c, or...

2) Write a new driver modeled on mdio-mux-gpio.c for your switch control.

Do you have a real device tree I can use as an example?

Attached.

I'm not sure what the "parent" MDIO bus node is supposed to represent.
  Is that that device that actually controls the muxing hardware

No.  It is the device that implements the master 802.3 clause {22,45} 
MDIO Station Management (STA) protocol.

, which in our case would be the FPGA?

I have no idea what your FPGA implements, so it is hard to say.

A sane person would implement a separate MDIO STA controller for each 
bus, in which case you wouldn't use the multiplexer driver.

Only people dealing with insane hardware need the multiplexer.  The 
patch in net-next has a nice ASCII art picture of such an insane design.

David Daney