[Precise][SRU][PATCH 1/1] x86 thermal: Disable power limit notification interrupt by default

[Luis Henriques]

From: Fenghua Yu <fenghua.yu at intel.com>

BugLink: http://bugs.launchpad.net/bugs/1215748

The package power limit notification interrupt is primarily for
system diagnosis, and should not be blindly enabled on every
system by default -- particuarly since Linux does nothing in the
handler except count how many times it has been called...

Add a new kernel cmdline parameter "int_pln_enable" for situations where
users want to oberve these events via existing system counters:

$ grep TRM /proc/interrupts

$ grep . /sys/devices/system/cpu/cpu*/thermal_throttle/*

https://bugzilla.kernel.org/show_bug.cgi?id=36182

Signed-off-by: Fenghua Yu <fenghua.yu at intel.com>
Signed-off-by: Len Brown <len.brown at intel.com>
Signed-off-by: Tony Luck <tony.luck at intel.com>
(back ported from commit 6bb2ff846f24fa6efee756e5e2a2b8433d65671e)
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 Documentation/kernel-parameters.txt      |  2 ++
 arch/x86/kernel/cpu/mcheck/therm_throt.c | 34 ++++++++++++++++++++++++--------
 2 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 5ce5e24..b35a20a 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1056,6 +1056,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 	inport.irq=	[HW] Inport (ATI XL and Microsoft) busmouse driver
 			Format: <irq>
 
+	int_pln_enable  [x86] Enable power limit notification interrupt
+
 	intel_iommu=	[DMAR] Intel IOMMU driver (DMAR) option
 		on
 			Enable intel iommu driver.
diff --git a/arch/x86/kernel/cpu/mcheck/therm_throt.c b/arch/x86/kernel/cpu/mcheck/therm_throt.c
index 25563ee..5b85e5d 100644
--- a/arch/x86/kernel/cpu/mcheck/therm_throt.c
+++ b/arch/x86/kernel/cpu/mcheck/therm_throt.c
@@ -212,6 +212,15 @@ static int thresh_event_valid(int event)
 	return 1;
 }
 
+static bool int_pln_enable;
+static int __init int_pln_enable_setup(char *s)
+{
+	int_pln_enable = true;
+
+	return 1;
+}
+__setup("int_pln_enable", int_pln_enable_setup);
+
 #ifdef CONFIG_SYSFS
 /* Add/Remove thermal_throttle interface for CPU device: */
 static __cpuinit int thermal_throttle_add_dev(struct sys_device *sys_dev,
@@ -224,7 +233,7 @@ static __cpuinit int thermal_throttle_add_dev(struct sys_device *sys_dev,
 	if (err)
 		return err;
 
-	if (cpu_has(c, X86_FEATURE_PLN))
+	if (cpu_has(c, X86_FEATURE_PLN) && int_pln_enable)
 		err = sysfs_add_file_to_group(&sys_dev->kobj,
 					      &attr_core_power_limit_count.attr,
 					      thermal_attr_group.name);
@@ -232,7 +241,7 @@ static __cpuinit int thermal_throttle_add_dev(struct sys_device *sys_dev,
 		err = sysfs_add_file_to_group(&sys_dev->kobj,
 					      &attr_package_throttle_count.attr,
 					      thermal_attr_group.name);
-		if (cpu_has(c, X86_FEATURE_PLN))
+		if (cpu_has(c, X86_FEATURE_PLN) && int_pln_enable)
 			err = sysfs_add_file_to_group(&sys_dev->kobj,
 					&attr_package_power_limit_count.attr,
 					thermal_attr_group.name);
@@ -345,7 +354,7 @@ static void intel_thermal_interrupt(void)
 				CORE_LEVEL) != 0)
 		mce_log_therm_throt_event(msr_val);
 
-	if (this_cpu_has(X86_FEATURE_PLN))
+	if (this_cpu_has(X86_FEATURE_PLN) && int_pln_enable)
 		therm_throt_process(msr_val & THERM_STATUS_POWER_LIMIT,
 					POWER_LIMIT_EVENT,
 					CORE_LEVEL);
@@ -355,7 +364,7 @@ static void intel_thermal_interrupt(void)
 		therm_throt_process(msr_val & PACKAGE_THERM_STATUS_PROCHOT,
 					THERMAL_THROTTLING_EVENT,
 					PACKAGE_LEVEL);
-		if (this_cpu_has(X86_FEATURE_PLN))
+		if (this_cpu_has(X86_FEATURE_PLN) && int_pln_enable)
 			therm_throt_process(msr_val &
 					PACKAGE_THERM_STATUS_POWER_LIMIT,
 					POWER_LIMIT_EVENT,
@@ -463,9 +472,13 @@ void intel_init_thermal(struct cpuinfo_x86 *c)
 	apic_write(APIC_LVTTHMR, h);
 
 	rdmsr(MSR_IA32_THERM_INTERRUPT, l, h);
-	if (cpu_has(c, X86_FEATURE_PLN))
+	if (cpu_has(c, X86_FEATURE_PLN) && !int_pln_enable)
+		wrmsr(MSR_IA32_THERM_INTERRUPT,
+			(l | (THERM_INT_LOW_ENABLE
+			| THERM_INT_HIGH_ENABLE)) & ~THERM_INT_PLN_ENABLE, h);
+	else if (cpu_has(c, X86_FEATURE_PLN) && int_pln_enable)
 		wrmsr(MSR_IA32_THERM_INTERRUPT,
-		      l | (THERM_INT_LOW_ENABLE
+			l | (THERM_INT_LOW_ENABLE
 			| THERM_INT_HIGH_ENABLE | THERM_INT_PLN_ENABLE), h);
 	else
 		wrmsr(MSR_IA32_THERM_INTERRUPT,
@@ -473,9 +486,14 @@ void intel_init_thermal(struct cpuinfo_x86 *c)
 
 	if (cpu_has(c, X86_FEATURE_PTS)) {
 		rdmsr(MSR_IA32_PACKAGE_THERM_INTERRUPT, l, h);
-		if (cpu_has(c, X86_FEATURE_PLN))
+		if (cpu_has(c, X86_FEATURE_PLN) && !int_pln_enable)
 			wrmsr(MSR_IA32_PACKAGE_THERM_INTERRUPT,
-			      l | (PACKAGE_THERM_INT_LOW_ENABLE
+				(l | (PACKAGE_THERM_INT_LOW_ENABLE
+				| PACKAGE_THERM_INT_HIGH_ENABLE))
+				& ~PACKAGE_THERM_INT_PLN_ENABLE, h);
+		else if (cpu_has(c, X86_FEATURE_PLN) && int_pln_enable)
+			wrmsr(MSR_IA32_PACKAGE_THERM_INTERRUPT,
+				l | (PACKAGE_THERM_INT_LOW_ENABLE
 				| PACKAGE_THERM_INT_HIGH_ENABLE
 				| PACKAGE_THERM_INT_PLN_ENABLE), h);
 		else
-- 
1.8.3.2