From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Boyd <sboyd@codeaurora.org>
Subject: Re: Delays, clocks, timers, hrtimers, etc
Date: Wed, 11 Feb 2015 15:26:31 -0800
Message-ID: <20150211232631.GE11190@codeaurora.org>
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To: Mason <mpeg.blue@free.fr>
Cc: Linux ARM <linux-arm-kernel@lists.infradead.org>, cpufreq <cpufreq@vger.kernel.org>, Linux PM <linux-pm@vger.kernel.org>, Mark Rutland <mark.rutland@arm.com>, Thomas Gleixner <tglx@linutronix.de>, Peter Zijlstra <peterz@infradead.org>, John Stultz <john.stultz@linaro.org>, Stefan Agner <stefan@agner.ch>, Shawn Guo <shawn.guo@linaro.org>, Rob Herring <robh@kernel.org>, Linus Walleij <linus.walleij@linaro.org>, Marc Zyngier <marc.zyngier@arm.com>

On 02/11, Mason wrote:
> 
> Looking at the difference between OF and !OF registration functions
> in smp_twd.c
> 
> !OF
>   if (twd_base || twd_evt) return -EBUSY;
>   assign twd_ppi and twd_base
>   twd_local_timer_common_register(NULL)
> 
> OF
>   if (!is_smp() || !setup_max_cpus) return; // TO BE DELETED
>   assign twd_ppi and twd_base
>   twd_local_timer_common_register(np)
> 
> I suppose OF guarantees that the init code is called only once?

It's called as many times as there's a match with the
corresponding CLOCKSOURCE_OF_DECLARE. In practice that's once.

> (Hence the !OF guard code would be unnecessary.)
> 

The other difference is that OF based registration needs to use
OF functions for irqs and ioremap whereas the non-OF code relies
on the irqs being provided before hand and the ioremap done
without OF functions.

-- 
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