linux-kernel - Re: [PATCH 33/36] AArch64: Generic timers support

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Message-Id: <201207131632.31548.arnd@arndb.de>
Date:	Fri, 13 Jul 2012 16:32:31 +0000
From:	Arnd Bergmann <arnd@...db.de>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	John Stultz <john.stultz@...aro.org>,
	Marc Zyngier <Marc.Zyngier@....com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Deepak Saxena <dsaxena@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Walleij <linus.ml.walleij@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Will Deacon <Will.Deacon@....com>,
	Mike Turquette <mike.turquette@...aro.org>,
	Marc Zyngier <maz@...terjones.org>
Subject: Re: [PATCH 33/36] AArch64: Generic timers support

On Friday 13 July 2012, Catalin Marinas wrote:
> > Architectures that always have a working clock source would then just
> > not include the timex.h header and #define ACT_HZ HZ in common code.
> 
> Would something like below be enough?
> 
> Also, are there any implications if we boot with clocksource=jiffies?
> 
> --- a/include/linux/jiffies.h
> +++ b/include/linux/jiffies.h
> @@ -55,7 +55,11 @@
>                               + ((((NOM) % (DEN)) << (LSH)) + (DEN) / 2) / (DEN))
>  
>  /* HZ is the requested value. ACTHZ is actual HZ ("<< 8" is for accuracy) */
> +#ifdef CLOCK_TICK_RATE
>  #define ACTHZ (SH_DIV (CLOCK_TICK_RATE, LATCH, 8))
> +#else
> +#define ACTHZ (HZ << 8)
> +#endif
>  
>  /* TICK_NSEC is the time between ticks in nsec assuming real ACTHZ */
>  #define TICK_NSEC (SH_DIV (1000000UL * 1000, ACTHZ, 8))
> 

I think that's a very good step in the right direction, yes.

It does not let us get rid of the asm/timex.h file, but that's actually
a separate problem. It also wouldn't hurt to put the LATCH definition
in the same #ifdef.

Acked-by: Arnd Bergmann <arnd@...db.de>

	Arnd

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