linux-kernel - Re: [sodaville] [PATCH 03/11] x86/dtb: Add a device tree for CE4100

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Date:	Thu, 2 Dec 2010 11:40:16 +1100
From:	David Gibson <david@...son.dropbear.id.au>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:	Mitch Bradley <wmb@...mworks.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	devicetree-discuss@...ts.ozlabs.org, sodaville@...utronix.de,
	x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [sodaville] [PATCH 03/11] x86/dtb: Add a device tree for CE4100

On Mon, Nov 29, 2010 at 08:44:45PM +0100, Sebastian Andrzej Siewior wrote:
> Mitch Bradley wrote:
> >On 11/28/2010 12:53 PM, Benjamin Herrenschmidt wrote:
> >>>I wasn't aware of the OFW binding for X86. I will follow it once I find
> >>>it.
> >>Interesting, I though I would find it on
> >>http://www.openfirmware.info/Bindings but it's not there...
> >>CC'ing Mitch who might know where to find that.
> >
> >I'd be happy to work with people to develop a new x86 binding.
> 
> So for the CPU node I have so far:
> 
>         cpus {
>                  #address-cells = <1>;
>                  #size-cells = <0>;
> 
>                  cpu@0 {
>                          device_type = "cpu";
> 			 compatible = "Intel,CE4100";
>                          reg = <0>;
>                          lapic = <&lapic0>;
>                  };
>          };
> 
> This one should match ePARP 1.0. David mentioned threads. I have just one.
> No HyperThreading, nothing special. Should I just leave it as it or go
> for:
>         cpus {
>                  #address-cells = <1>;
>                  #size-cells = <0>;
> 
>                  cpu@0 {
>                          device_type = "cpu";
> 			 compatible = "Intel,CE4100";	
> 			 reg = <0>;
>                	         lapic = <&lapic0>;
> 
> 			thread@0 {
>         	                 reg = <0>;
>                  	};
> 		};
>          };
> ?

Leave it as is.  For hyperthreading there's a good chance you'll be
able to get away with the simple extension we're planning to use in
ePAPR 1.1, which would be:
	cpu@0 {
		...
		reg = <0 1 2 3>;
		...
	};

For, e.g. a cpu with 4 threads.

If more detailed per-thread information is needed then we or you might
want sub-nodes one day.  But even if we do that, we should allow them
to be omitted in the single-thread case.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson
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