linux-kernel - [09/68] x86, hpet: Disable per-cpu hpet timer if ARAT is supported

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Date:	Mon, 28 Feb 2011 08:22:30 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Shaohua Li <shaohua.li@...el.com>,
	venkatesh.pallipadi@...el.com, Ingo Molnar <mingo@...e.hu>,
	Thomas Renninger <trenn@...e.de>
Subject: [09/68] x86, hpet: Disable per-cpu hpet timer if ARAT is supported

2.6.32-longterm review patch.  If anyone has any objections, please let us know.

------------------

From: Shaohua Li <shaohua.li@...el.com>

commit 39fe05e58c5e448601ce46e6b03900d5bf31c4b0 upstream.

If CPU support always running local APIC timer, per-cpu hpet
timer could be disabled, which is useless and wasteful in such
case. Let's leave the timers to others.

The effect is that we reserve less timers.

Signed-off-by: Shaohua Li <shaohua.li@...el.com>
Cc: venkatesh.pallipadi@...el.com
LKML-Reference: <20090812031612.GA10062@...10-desk.sh.intel.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
Cc: Thomas Renninger <trenn@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 arch/x86/kernel/hpet.c |   12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -606,6 +606,8 @@ static void hpet_msi_capability_lookup(u
 	if (hpet_msi_disable)
 		return;
 
+	if (boot_cpu_has(X86_FEATURE_ARAT))
+		return;
 	id = hpet_readl(HPET_ID);
 
 	num_timers = ((id & HPET_ID_NUMBER) >> HPET_ID_NUMBER_SHIFT);
@@ -894,10 +896,8 @@ int __init hpet_enable(void)
 
 	if (id & HPET_ID_LEGSUP) {
 		hpet_legacy_clockevent_register();
-		hpet_msi_capability_lookup(2);
 		return 1;
 	}
-	hpet_msi_capability_lookup(0);
 	return 0;
 
 out_nohpet:
@@ -930,12 +930,20 @@ static __init int hpet_late_init(void)
 	if (!hpet_virt_address)
 		return -ENODEV;
 
+	if (hpet_readl(HPET_ID) & HPET_ID_LEGSUP)
+		hpet_msi_capability_lookup(2);
+	else
+		hpet_msi_capability_lookup(0);
+
 	hpet_reserve_platform_timers(hpet_readl(HPET_ID));
 	hpet_print_config();
 
 	if (hpet_msi_disable)
 		return 0;
 
+	if (boot_cpu_has(X86_FEATURE_ARAT))
+		return 0;
+
 	for_each_online_cpu(cpu) {
 		hpet_cpuhp_notify(NULL, CPU_ONLINE, (void *)(long)cpu);
 	}


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