[PATCH] [v3] power/fsl: add MDIO dt binding for FMan

[Shaohui Xie]

> -----Original Message-----
> From: Wood Scott-B07421
> Sent: Thursday, January 08, 2015 9:13 AM
> To: Medve Emilian-EMMEDVE1
> Cc: Xie Shaohui-B21989; linuxppc-dev at lists.ozlabs.org;
> devicetree at vger.kernel.org
> Subject: Re: [PATCH] [v3] power/fsl: add MDIO dt binding for FMan
> 
> On Wed, 2015-01-07 at 13:44 -0600, Emil Medve wrote:
> > Hello Scott,
> >
> >
> > On 01/07/2015 12:05 PM, Scott Wood wrote:
> > > On Tue, 2015-01-06 at 23:29 -0600, Xie Shaohui-B21989 wrote:
> > >>>>> +- interrupts
> > >>>>> +		Usage: optional
> > >>>>> +		Value type: <prop-encoded-array>
> > >>>>> +		Definition: Event interrupt of external MDIO controller.
> > >>>>> +		1 Gb/s MDIO and 10 Gb/s MDIO has one interrupt respectively.
> > >>>
> > >>> I'm confused by "respectively" here.  Does fsl,fman-memac-mdio
> > >>> have two interrupts (one for 1 Gb/s and one for 10 Gb/s)?
> > >> [S.H] We use two MDIO controllers for external PHY management. One
> > >> for 1 Gb/s, One for 10 Gb/s, and two MDIO interrupts connected to MPIC.
> > >
> > > If there can be two interrupts you need to make that clear and
> > > specify the order.
> > >
> > > Is it possible for one MDIO controller to have an interrupt
> > > connected but not the other, on the same system?  How would you
> > > represent that in the device tree?  If there are two MDIO
> > > controllers why are they in the same node?
> >
> > Historically (FMan v2 and even before/legacy) we've had each MAC
> > include an MDIO controller, but only one MDIO controller per MAC
> > type/speed (1 Gb/s vs 10 Gb/s) is pinned out and all the same speed
> > PHY(s) are connected to the respective MDIO controllers. As such the
> > first 1 Gb/s MAC/MDIO controller is used to manage all the 1 Gb/s
> > PHY(s) and the first 10 Gb/s MAC/MDIO controller is used to manage all
> > the 10 Gb/s PHY(s). Each MDIO controller has the ability to generate
> > interrupts but only pinned out MDIO controllers are hooked up to the
> > MPIC (as such the talk about two interrupts)
> >
> > (Each MAC has also integrated a SERDES/TBI/"internal" PHY that is
> > connected to the "local" MDIO controller)
> >
> > As you can imagine this creates a number of problems in a partitioning
> > scenario (and not just, imagine RCWs where the first MAC is not
> > used/enabled). In order to help a bit (but not quite enough), in FMan
> > v3, two additional MDIO controllers (one for 1 the Gb/s PHY(s) and one
> > for 1 the 10 Gb/s PHY(s)) have been integrated that are not associated
> > with any MAC and these are the pinned out MDIO controllers on such
> > SoC(s) (chassis v2)
> 
> I'm happy to hear that.  Is that what is meant by "external" here?  I thought it
> meant external to the SoC.  Is this the term used by hardware documentation?
[S.H] Yes. "external" & "internal" are used by hardware documentation.

> I'd have called it "independent" or similar.
> 
> > >>   Does "optional" mean it's used if and
> > >>> only if external MDIO is used, or is it optional even with
> > >>> external MDIO?  I see it's not present in the example -- do we not
> > >>> have a real example that has the interrupt?
> > >> [S.H] "optional" means it's available on hardware, but MDIO driver does not
> use interrupt.
> > >> So we don't have a real example.
> > >
> > > <record type="broken">The device tree describes the hardware, not
> > > the driver</record>
> >
> > Anyway, only two MDIO nodes (out of 4 to 14) would have an interrupt
> > property describing exactly one interrupt. What language should we use
> > to convey this situation
> 
> So the answer is that there will not be more than one MDIO controller per MDIO
> node, or more than one interrupt per MDIO node? 
[S.H] Yes, one MDIO controller per MDIO node, and one interrupt per "external"
MDIO node.

 In that case just get rid of
> the confusing "respectively" sentence -- and always describe the interrupt if it
> exists in hardware.
[S.H] OK.

Thanks!
Shaohui