linux-kernel - Re: [PATCH -tip] x86: apic LVTT - use APIC

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Message-ID: <20080712073910.GA10689@elte.hu>
Date:	Sat, 12 Jul 2008 09:39:10 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Cyrill Gorcunov <gorcunov@...il.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Maciej W. Rozycki" <macro@...ux-mips.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -tip] x86: apic LVTT - use APIC_DIVISOR on 64bit mode


* Cyrill Gorcunov <gorcunov@...il.com> wrote:

> @@ -329,7 +332,7 @@ static void __init calibrate_APIC_clock(
>  	 *
>  	 * No interrupt enable !
>  	 */
> -	__setup_APIC_LVTT(250000000, 0, 0);
> +	__setup_APIC_LVTT(4000000000, 0, 0);

note how close it is to 2^32. For this to be unifiable later on this 
needs to be UL i guess, and this:

> -	calibration_result = result / HZ;
> +	calibration_result = result * APIC_DIVISOR / HZ;

might overflow 32 bits.

	Ingo
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