linux-kernel - Re: [PATCH v3] ARM: at91: Document new TCB bindings

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Message-ID: <20160704121127.GG20045@piout.net>
Date:	Mon, 4 Jul 2016 14:11:27 +0200
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:	Nicolas Ferre <nicolas.ferre@...el.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Thierry Reding <thierry.reding@...il.com>,
	linux-pwm@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v3] ARM: at91: Document new TCB bindings

On 04/07/2016 at 14:03:58 +0200, Boris Brezillon wrote :
> On Mon, 4 Jul 2016 12:36:31 +0200
> Alexandre Belloni <alexandre.belloni@...e-electrons.com> wrote:
> 
> > On 04/07/2016 at 12:24:52 +0200, Boris Brezillon wrote :
> > > On Fri,  1 Jul 2016 23:52:05 +0200
> > > Alexandre Belloni <alexandre.belloni@...e-electrons.com> wrote:  
> > > > +One interrupt per TC block:
> > > > +	tcb0: timer@...7c000 {
> > > > +		compatible = "atmel,at91rm9200-tcb", "simple-mfd", "syscon";
> > > > +		#address-cells = <1>;
> > > > +		#size-cells = <0>;
> > > > +		reg = <0xfff7c000 0x100>;
> > > > +		interrupts = <18 4>;
> > > > +		clocks = <&tcb0_clk>, <&clk32k>;
> > > > +		clock-names = "t0_clk", "slow_clk";
> > > > +
> > > > +		timer@0 {
> > > > +			compatible = "atmel,tcb-timer";
> > > > +			reg = <0>, <1>;
> > > > +		};
> > > > +
> > > > +		timer@2 {
> > > > +			compatible = "atmel,tcb-timer";
> > > > +			reg = <2>;
> > > > +		};  
> > > 
> > > And how can you differentiate the clocksource from the clkevent?
> > >   
> > 
> > It doesn't really matter actually, I'll do the selection in the driver,
> > as suggested by Rob.
> > 
> 
> Yes, I've read Rob's review, but then what's the point of defining 2
> timer nodes, just do the detection based on the number of channels
> you've reserved for the timer and define a single node.

I agree this is a really hypothetical use case but one may want to have
the clocksource on one TCB and the clockevent on another. This would
allow to have for example a quadrature decoder and the clocksource on
one TCB and another quadrature decoder and the clockevent device on
another TCB.


-- 
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com