linux-kernel - Re: [PATCH 2/9] ARC: [dts] Introduce Timer bindings

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Date:	Tue, 16 Feb 2016 14:14:20 +0530
From:	Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:	Rob Herring <robh@...nel.org>
CC:	arcml <linux-snps-arc@...ts.infradead.org>,
	Alexey Brodkin <Alexey.Brodkin@...opsys.com>,
	Noam Camus <noamc@...hip.com>,
	lkml <linux-kernel@...r.kernel.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH 2/9] ARC: [dts] Introduce Timer bindings

On Wednesday 03 February 2016 09:09 PM, Rob Herring wrote:
> On Wed, Feb 3, 2016 at 2:04 AM, Vineet Gupta <Vineet.Gupta1-HKixBCOQz3hWk0Htik3J/w@...lic.gmane.org> wrote:
>> Hi Rob,
>>
>> On Wednesday 03 February 2016 03:33 AM, Rob Herring wrote:
>>> On Tue, Feb 02, 2016 at 04:28:52PM +0530, Vineet Gupta wrote:
>>>> +Required properties:
>>>> +
>>>> +- compatible : should be "snps,arc-timer0"
>>>
>>> timer0 and timer1 are different h/w blocks, not just different
>>> instances?
>>
>> Functionality wise they are identical (only the address of aux regs used to
>> program them are different). Either can be configured to interrupt-on-limit or
>> free-run-and-wrap-around. So we can indeed consider them 2 instances. ARC Linux
>> uses timer0 for tick handling, timer1 for gtod.
>>
>> Do you prefer they not be differentiated as timer0 and timer1 ?
>>
>> So we have
>>
>> CLOCKSOURCE_OF_DECLARE(arc_clkevt, "snps,arc-timer0", arc_clockevent_setup);
>> CLOCKSOURCE_OF_DECLARE(arc_timer1, "snps,arc-timer1", arc_cs_setup_timer1);
>>
>> I don't know how to achieve above, by keeping the DT names the same.
> 
> You just need a single CLOCKSOURCE_OF_DECLARE which will be called
> twice. On the first call, setup one timer and on the 2nd call setup
> the other one. IIRC the sp804 timer has something similar.
> 
> You'll need a unit address in the node name to distinguish them.

So this is just to distinguish them in DT, but the callback uses a static counter
to do 1st vs. 2nd (and this unit address is not really exposed to code) - correct ?