linux-kernel - [PATCH 2/2] x86/apic: check global clockevent in lapic timer setup

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Date:	Thu, 17 Dec 2009 09:59:23 -0800
From:	"Pan, Jacob jun" <jacob.jun.pan@...el.com>
To:	"H. Peter Anvin" <hpa@...ux.intel.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>
Subject: [PATCH 2/2] x86/apic: check global clockevent in lapic timer setup

>From 5b3b795b42796e326d34713d4785c161b52e04db Mon Sep 17 00:00:00 2001
From: Jacob Pan <jacob.jun.pan@...el.com>
Date: Thu, 17 Dec 2009 08:07:57 -0800
Subject: [PATCH 2/2] x86/apic: check global clockevent in lapic timer setup

Global clockevent is needed to calibrate local apic timer.
This patch makes sure we have a valid global clockevent prior
to lapic timer setup.
Non-pc x86 mid platform with per cpu platform timer may not
have a global clockevent device.

Signed-off-by: Jacob Pan <jacob.jun.pan@...el.com>
---
 arch/x86/kernel/apic/apic.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index aa57c07..7e7aee1 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -724,6 +724,13 @@ static int __init calibrate_APIC_clock(void)
  */
 void __init setup_boot_APIC_clock(void)
 {
+	/* global clockevent is needed for calibration */
+	if (!global_clock_event) {
+		apic_printk(APIC_DEBUG,
+				"no global clockevent for calibration\n");
+		return;
+	}
+
 	/*
 	 * The local apic timer can be disabled via the kernel
 	 * commandline or from the CPU detection code. Register the lapic
-- 
1.6.5.3

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