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

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Date:	Wed, 9 Jul 2008 23:02:37 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
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: [PATCH -tip] x86: apic LVTT - use APIC_DIVISOR on 64bit mode

We use APIC_TDR_DIV_16 while setting APIC_TDCR (divisor)
it happened this moment is hidden from __setup_APIC_LVTT
caller. So we better increment caller 'clocks' value to
not change current behaviour and use APIC_DIVISOR
(as already done in 32bit version).

The main benefit - unified procedure code for 32/64bit modes.

Signed-off-by: Cyrill Gorcunov <gorcunov@...il.com>
CC: "Maciej W. Rozycki" <macro@...ux-mips.org>
---

Please review carefully. Any comments are welcome.
I'm _not_ 100% sure if this patch is safe.

Index: linux-2.6.git/arch/x86/kernel/apic_64.c
===================================================================
--- linux-2.6.git.orig/arch/x86/kernel/apic_64.c	2008-07-08 22:52:24.000000000 +0400
+++ linux-2.6.git/arch/x86/kernel/apic_64.c	2008-07-08 23:00:24.000000000 +0400
@@ -165,6 +165,9 @@ int lapic_get_maxlvt(void)
 	return maxlvt;
 }
 
+/* Clock divisor is set to 16 */
+#define APIC_DIVISOR 16
+
 /*
  * This function sets up the local APIC timer, with a timeout of
  * 'clocks' APIC bus clock. During calibration we actually call
@@ -197,7 +200,7 @@ static void __setup_APIC_LVTT(unsigned i
 				| APIC_TDR_DIV_16);
 
 	if (!oneshot)
-		apic_write(APIC_TMICT, clocks);
+		apic_write(APIC_TMICT, clocks/APIC_DIVISOR);
 }
 
 /*
@@ -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);
 
 	apic_start = apic_read(APIC_TMCCT);
 #ifdef CONFIG_X86_PM_TIMER
--
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