Re: [PATCH RFT 1/2] phylib: add device reset GPIO support

[Sergei Shtylyov]

Hello.

On 05/14/2016 02:44 AM, Andrew Lunn wrote:

> > > > > Another issue is that on some boards we have one reset line tied to
> > > > > multiple PHYs.How do we prevent multiple resets being taking place when each of
> > > > > the PHYs are registered?
> > > >
> > > >   My patch just doesn't address this case -- it's about the
> > > > individual resets only.
> > >
> > > This actually needs to be addresses a layer above. What you have is a
> > > bus reset, not a device reset.
> >
> >    No.
> >    There's simply no such thing as a bus reset for the xMII/MDIO
> > busses, there's simply no reset signaling on them. Every device has
> > its own reset signal and its own timing requirements.
>
> Except in the case above, where two phys are sharing the same reset
> signal. So although it is not part of the mdio standard to have a bus
> reset, this is in effect what the gpio line is doing, resetting all
> devices on the bus. If you don't model that as a bus reset, how do you
> model it?

   I'm not suggesting that the shared reset should be handled by my patch. 
Contrariwise, I suggested to use the mii_bus::reset() method -- I see it as a 
necessary evil. However, in the more common case of a single PHY, this method 
simply doesn't scale -- you'd have to teach each and every individual MAC/ 
MDIO driver to do the GPIO reset trick.

>       Andrew

MBR, Sergei