linux-kernel - Re: [PATCH 03/10] clocksource: Remove clocksource_max

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Message-ID: <20150111114724.GE4467@localhost.localdomain>
Date:	Sun, 11 Jan 2015 12:47:25 +0100
From:	Richard Cochran <richardcochran@...il.com>
To:	John Stultz <john.stultz@...aro.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...emonkey.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Prarit Bhargava <prarit@...hat.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 03/10] clocksource: Remove clocksource_max_deferment()


This series added:

+	/* Return 50% of the actual maximum, so we can detect bad values */
+	max_nsecs >>= 1;

and then...

On Fri, Jan 09, 2015 at 04:34:21PM -0800, John Stultz wrote:
> @@ -760,7 +746,8 @@ void __clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq)
>  		cs->maxadj = clocksource_max_adjustment(cs);
>  	}
>  
> -	cs->max_idle_ns = clocksource_max_deferment(cs);
> +	cs->max_idle_ns = clocks_calc_max_nsecs(cs->mult, cs->shift,
> +						 cs->maxadj, cs->mask);
>  }
>  EXPORT_SYMBOL_GPL(__clocksource_updatefreq_scale);
>  
> @@ -807,7 +794,8 @@ int clocksource_register(struct clocksource *cs)
>  		cs->name);
>  
>  	/* calculate max idle time permitted for this clocksource */
> -	cs->max_idle_ns = clocksource_max_deferment(cs);
> +	cs->max_idle_ns = clocks_calc_max_nsecs(cs->mult, cs->shift,
> +						 cs->maxadj, cs->mask);

... the whole world's maximum idle time is artificially reduced by
half in order to catch some rare HW bug?  Not a very green solution.

Thanks,
Richard
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