linux-kernel - [RFC PATCH v2 04/12] x86/time: Initialize interrupt mode behind timer init

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Date:   Wed, 19 Apr 2017 17:05:18 +0800
From:   Dou Liyang <douly.fnst@...fujitsu.com>
To:     <x86@...nel.org>, <linux-kernel@...r.kernel.org>
CC:     <tglx@...utronix.de>, <mingo@...nel.org>, <hpa@...or.com>,
        <ebiederm@...ssion.com>, <bhe@...hat.com>,
        <izumi.taku@...fujitsu.com>, Dou Liyang <douly.fnst@...fujitsu.com>
Subject: [RFC PATCH v2 04/12] x86/time: Initialize interrupt mode behind timer init

In start_kernel(), firstly, it works on the default interrupy mode, then
switch to the final mode. default mode may not be compatible with the
actual hardware, which cause the delivery interrupt to fail.

Try to set up the final mode as soon as possible. according to the parts
which split from that initialization:

1) Set up the APIC/IOAPIC (including testing whether the timer
   interrupt works)

2) Calibrate TSC

3) Set up the local APIC timer

-- From Thomas Gleixner

Initializing the mode should be earlier than calibrating TSC and needs
testing whether the timer interrupt works at the same time.

Add init_interrupt_mode() to the right location in x86_late_time_init().

Signed-off-by: Dou Liyang <douly.fnst@...fujitsu.com>
---
 arch/x86/kernel/time.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/x86/kernel/time.c b/arch/x86/kernel/time.c
index d39c091..04139c8 100644
--- a/arch/x86/kernel/time.c
+++ b/arch/x86/kernel/time.c
@@ -21,6 +21,7 @@
 #include <asm/timer.h>
 #include <asm/hpet.h>
 #include <asm/time.h>
+#include <asm/apic.h>
 
 #ifdef CONFIG_X86_64
 __visible volatile unsigned long jiffies __cacheline_aligned = INITIAL_JIFFIES;
@@ -84,6 +85,13 @@ void __init hpet_time_init(void)
 static __init void x86_late_time_init(void)
 {
 	x86_init.timers.timer_init();
+
+	/*
+	 * After PIT/HPET timers init, select and setup
+	 * the final interrupt mode for delivering IRQs.
+	 */
+	init_interrupt_mode();
+
 	tsc_init();
 }
 
-- 
2.5.5