RE: [PATCH] powerpc/fsl: Add FMan best effort port compatible

[Liberman Igal <Igal.Liberman-KZfg59tc24xl57MIdRCFDg@public.gmane.org>]

Hi Scott,
I understand your point, let me please explain more about the hardware configuration and suggest another solution.
I'm referring only to external ports (TX/RX), not OP.
In FMan V3 we have maximum of 8 Port, it depends on the FMan revision (in B4, T2, T4 we have 8 ports, in T1024 and T1040 we have 4).
The following configuration are valid:
	- All 8 ports can work as 1G ports. 
	- Ports 7, 8 (if available) can work as 10G (with full hardware resources).
	- Port 1, 2 (1 in T1024; 1, 2 in T2080) can be configured as 10G (with limited hardware resources).

Currently we use only "fsl,fm-v3-port-rx/tx".

We can go 2 ways:
1. Having 2 compatibles:
	"fsl,fman-v3-port-rx/tx"
	"fsl,fman-v3-best-effort-port-rx/tx"

	The driver can determine the port type of "fsl,fman-v3-port-rx/tx" by reading the HW port id.
	"fsl,fman-v3-best-effort-port-rx/tx" will let the driver know about the best effort port and it will be used instead of "fsl,fman-v3-port-rx/tx".

In your opinion, should we add "fsl,fman-v3-10g-port-rx/tx" for 10G (with full hardware resources)?
In such chase, "fsl,fman-v3-port-rx/tx" will denote 1G explicitly.

In FMan V2, dual ports/MACs are not available, so no need change the compatibles.

Igal

> -----Original Message-----
> From: Wood Scott-B07421
> Sent: Tuesday, May 19, 2015 12:09 AM
> To: Liberman Igal-B31950
> Cc: devicetree@vger.kernel.org; linuxppc-dev@lists.ozlabs.org; Bucur
> Madalin-Cristian-B32716
> Subject: Re: [PATCH] powerpc/fsl: Add FMan best effort port compatible
> 
> On Mon, 2015-05-18 at 11:41 +0300, Igal.Liberman wrote:
> > From: Igal Liberman <igal.liberman@freescale.com>
> >
> > This patch adds a compatible which represents FMan V3 best effort ports.
> > FMan best effort port is configured as 10G ports, however, it uses 1G
> > hardware.
> >
> > Signed-off-by: Igal Liberman <igal.liberman@freescale.com>
> > ---
> >  .../devicetree/bindings/powerpc/fsl/fman.txt       |    5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/powerpc/fsl/fman.txt
> > b/Documentation/devicetree/bindings/powerpc/fsl/fman.txt
> > index edda55f..c2e3ec3 100644
> > --- a/Documentation/devicetree/bindings/powerpc/fsl/fman.txt
> > +++ b/Documentation/devicetree/bindings/powerpc/fsl/fman.txt
> > @@ -166,6 +166,11 @@ PROPERTIES
> >  			- "fsl,fman-v3-port-oh" for FManV3 OH ports
> >  			- "fsl,fman-v3-port-rx" for FManV3 RX ports
> >  			- "fsl,fman-v3-port-tx" for FManV3 TX ports
> > +		Optional compatible which can be used in addition to the
> > +		compatibles above is:
> > +			- "fsl,fman-v3-best-effort-port"
> > +		This compatible represents 10G best effort ports:
> > +			Port configured as 10G, using 1G hardware.
> 
> What does this mean?  If it's using 1G hardware then it's a 1G port, right?
> How can you configure a 1G port to be 10G?
> 
> Why is this compatible in addition to others (note that this implies such ports
> are 100% backwards compatible with hardware that lacks the new
> compatible)?  You'd have the same compatible on rx and tx nodes (I'm
> assuming this isn't applicable to oh)?
> 
> What are the implications of this that warrant adding a compatible?
> 
> -Scott
>