CPM2 mii-bitbang: Allowing mdio on port pins other than port C

[Mark Ware]

Hi Laurent,


> -----Original Message-----
> From: Laurent Pinchart [mailto:laurentp at cse-semaphore.com] 
> Sent: Monday, 16 June 2008 18:53
> To: linuxppc-dev at ozlabs.org
> Cc: Mark Ware
> Subject: Re: CPM2 mii-bitbang: Allowing mdio on port pins 
> other than port C
> 
> Hi Mark,
> 
> On Monday 16 June 2008 08:19, Mark Ware wrote:
> > Hello,
> > 
> > I am preparing a board port (from 2.4.18!) for a proprietary board 
> > which has it's mdio on a different port than mdc.  The current 
> > mii-bitbang driver in fs_enet assumes both pins are 
> connected to port 
> > C.  I have created a fairly simple patch to make this more 
> flexible, 
> > but I'm new to device trees and am unsure how best to describe the 
> > situation in the dts.
> > 
> > The current mdio node for CPM2 looks something like:
> > 
> > mdio at 10d40 {
> >   device_type = "mdio";
> >   compatible = "fsl,cpm2-mdio-bitbang";
> >   #address-cells = <1>;
> >   #size-cells = <0>
> >   reg = <0x10d40 0x14>;
> >   fsl,mdio-pin = <12>;
> >   fsl,mdc-pin = <15>;
> > }
> > 
> > I have made mdio work on our board by adding a second reg range and 
> > using the first one for mdc and the second one for mdio:
> > 
> >   reg = <0x10d40 0x14 0x10d60 0x14>;  // mdc=port D, mdio=port A
> >   fsl,mdio-pin = <12>;    		  // PD12
> >   fsl,mdc-pin = <15>;     		  // PC15
> > 
> > The code remains backwards compatible, in that if only one 
> reg range 
> > is present it is used for both.
> > 
> > Is this a valid (and acceptable) way to extend the reg property?
> 
> It is. Sergej Stepanov submitted similar patches some times 
> ago. You can find them at
> 
> http://www.spinics.net/lists/netdev/msg45778.html
> http://www.spinics.net/lists/netdev/msg47159.html
> 
> > Is their a cleaner way I should look at?
> 
> Using the GPIO lib might be cleaner. Have a look at 
> http://www.nabble.com/-PATCH-0-2--MDIO-on-GPIO-support-for-the
> -fs_enet-driver-ts17468958.html
> for a patch.
> 

Thanks for the links.  It looks like I should have been searching in
netdev not powerpc for this.

I will look at Sergej's patch and perhaps submit a merged version, but
with the GPIO version likely to be merged is there much point?  The GPIO
lib method appears to be a more generic replacement.

Regards,
Mark