linux-kernel - Re: [PATCH 12/12] clocksource: Add some debug info about clocksources being registered

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Date:	Sat, 7 Mar 2015 10:50:19 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	John Stultz <john.stultz@...aro.org>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...emonkey.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Richard Cochran <richardcochran@...il.com>,
	Prarit Bhargava <prarit@...hat.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 12/12] clocksource: Add some debug info about
 clocksources being registered


* John Stultz <john.stultz@...aro.org> wrote:

> Print the mask, max_cycles, and max_idle_ns values for clocksources
> being registered.
> 
> Cc: Dave Jones <davej@...emonkey.org.uk>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Richard Cochran <richardcochran@...il.com>
> Cc: Prarit Bhargava <prarit@...hat.com>
> Cc: Stephen Boyd <sboyd@...eaurora.org>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Signed-off-by: John Stultz <john.stultz@...aro.org>
> ---
>  kernel/time/clocksource.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
> index 3f24bb3..9b75316 100644
> --- a/kernel/time/clocksource.c
> +++ b/kernel/time/clocksource.c
> @@ -697,6 +697,10 @@ void __clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq)

So that name should really be something like __clocksource_update_freq_scale(),
right?

>  	cs->max_idle_ns = clocks_calc_max_nsecs(cs->mult, cs->shift,
>  						 cs->maxadj, cs->mask,
>  						 &cs->max_cycles);
> +
> +	pr_info("clocksource %s: mask: 0x%llx max_cycles: 0x%llx, max_idle_ns: %lld ns\n",
> +			cs->name, cs->mask, cs->max_cycles, cs->max_idle_ns);
> +

Also, why is this function exported? No in-tree module uses it.

Also, when I read the code, I noticed:

/**
 * __clocksource_updatefreq_scale - Used update clocksource with new freq
 * @cs:         clocksource to be registered
 * @scale:      Scale factor multiplied against freq to get clocksource hz
 * @freq:       clocksource frequency (cycles per second) divided by scale
 *
 * This should only be called from the clocksource->enable() method.
 *
 * This *SHOULD NOT* be called directly! Please use the
 * clocksource_updatefreq_hz() or clocksource_updatefreq_khz helper functions.

One more reason to not export it?

Also, typo in the description.

Plus, one helper function is marked with '()', the other not ...

Thanks,

	Ingo
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