[PATCH 1/8] Documentation: devicetree: Update Exynos MCT bindings description

[t.figa@samsung.com (Tomasz Figa)]

On Tuesday 20 of August 2013 11:00:53 Stephen Warren wrote:
> On 08/20/2013 07:52 AM, Tomasz Figa wrote:
> > This patch updates description of device tree bindings for Exynos MCT
> > 
> > (multicore timers). Namely:
> >  - added note about simplified specification of local timer interrupts,
> >  
> >    when using single per-processor interrupt for all local timers,
> >  
> >  - changed first example that was incorrectly suggesting that global
> >  
> >    timer interrupts are optional,
> >  
> >  - simplified example interrupt map,
> >  - added example showing simplified local timer interrupt
> >  specification.
> > 
> > diff --git
> > a/Documentation/devicetree/bindings/timer/samsung,exynos4210-mct.txt
> > b/Documentation/devicetree/bindings/timer/samsung,exynos4210-mct.txt
> > 
> > -Example 1: In this example, the system uses only the first global
> > timer
> > -	   interrupt generated by MCT and the remaining three global timer
> > -	   interrupts are unused. Two local timer interrupts have been
> > -	   specified.
> > +  For MCT block that uses a per-processor interrupt for local timers,
> > such +  as ones compatible with "samusng,exynos4412-mct", only one
> > local timer
> samsung is typo'd there.

Oops. ;)

> > +Example 2: In this example, the timer interrupts are connected to two
> > separate +	   interrupt controllers. Hence, an interrupt-map is
> > created to map +	   the interrupts to the respective interrupt
> > controllers.
> > 
> >  	mct at 101C0000 {
> >  	
> >  		compatible = "samsung,exynos4210-mct";
> >  		reg = <0x101C0000 0x800>;
> > 
> > -		interrupt-controller;
> > -		#interrups-cells = <2>;
> > 
> >  		interrupt-parent = <&mct_map>;
> > 
> > -		interrupts = <0 0>, <1 0>, <2 0>, <3 0>,
> > -			     <4 0>, <5 0>;
> > +		interrupts = <0>, <1>, <2>, <3>, <4>, <5>;
> > 
> >  		mct_map: mct-map {
> > 
> > -			#interrupt-cells = <2>;
> > +			#interrupt-cells = <1>;
> > 
> >  			#address-cells = <0>;
> >  			#size-cells = <0>;
> 
> I don't believe you need either of those two properties in a node solely
> used as an interrupt map.

Well, you don't need #size-cells, as it is not used for interrupt-map 
property.

As for #address-cell property, you need it, as it defines how many cells 
are used in interrupt map specifier for unit address. See ePAPR 2.4.3.1 or 
[1] for a description of interrupt-map property format.

[1] - http://devicetree.org/Device_Tree_Usage#Advanced_Interrupt_Mapping

> Also, why not put the interrupt-map property directly into the main mct
> node; I don't believe there's any requirement nor advantage to it being
> a separate node.

It is more readable, as you don't mix virtual (helper) properties, with 
those describing the hardware. Otherwise both ways are technically correct, 
but not for all cases, i.e. only when #address-cells and #interrupt-cells 
properties aren't used for device's own purposes.

> > -			interrupt-map = <0x0 0 &combiner 23 3>,
> > -					<0x4 0 &gic 0 120 0>,
> > -					<0x5 0 &gic 0 121 0>;
> > +			interrupt-map = <0 &gic 0 57 0>,
> > +					<1 &gic 0 69 0>,
> > +					<2 &combiner 12 6>,
> > +					<3 &combiner 12 7>,
> > +					<4 &gic 0 42 0>,
> > +					<5 &gic 0 48 0>;
> > 
> >  		};
> >  	
> >  	};
> > 
> > +Example 3: In this example, the IP contains four local timers, but
> > using +	   a per-processor interrupt to handle them. Either all the
> > local +	   timer interrupts can be specified, with the same interrupt
> > specifier +	   value or just the first one.
> 
> That sounds like it should be two separate examples.
> 
> Actually, there's already a 2-timer example above using separate
> interrupts, so why not make this example *just* be for the
> single-interrupt case?

Well, I wanted to show that both ways of specification would be equivalent 
here. If you insist on making it a single example, then I can send next 
version with this changed.

Best regards,
Tomasz