linux-kernel - [PATCH] x86, apic: Clear APIC Timer Initial Count Register on shutdown

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Message-ID: <20091027100138.GB30802@alberich.amd.com>
Date:	Tue, 27 Oct 2009 11:01:38 +0100
From:	Andreas Herrmann <herrmann.der.user@...glemail.com>
To:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] x86, apic: Clear APIC Timer Initial Count Register on
 shutdown


Commit a98f8fd24fb24fcb9a359553e64dd6aac5cf4279 (x86: apic reset
counter on shutdown) set the counter to max to avoid spurious
interrupts when the timer is re-enabled.

(In theory) you'll still get a spurious interrupt if spending more
than 344 seconds with this interrupt disabled and then unmasking it.

The right thing to do is to clear the register. This disables the
interrupt from happening (at least it does on AMD hardware).

Signed-off-by: Andreas Herrmann <andreas.herrmann3@....com>
---
 arch/x86/kernel/apic/apic.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index dce93d4..4c689f4 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -444,7 +444,7 @@ static void lapic_timer_setup(enum clock_event_mode mode,
 		v = apic_read(APIC_LVTT);
 		v |= (APIC_LVT_MASKED | LOCAL_TIMER_VECTOR);
 		apic_write(APIC_LVTT, v);
-		apic_write(APIC_TMICT, 0xffffffff);
+		apic_write(APIC_TMICT, 0);
 		break;
 	case CLOCK_EVT_MODE_RESUME:
 		/* Nothing to do here */
-- 
1.6.2.5

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