acpi: Don't let acpi_pad needlessly mark TSC unstable
PATCH 1/1 acpi: Don't let acpi_pad needlessly mark TSC unstable
acpi pad driver kind of aggressively marks TSC as unstable at init time, on mwait capable and non X86_FEATURE_NONSTOP_TSC systems. This is irrespective of whether pad driver is ever going to be used on the system or deep C-states are supported/used. This will affect every user who just happens to compile in (or get a kernel version which compiles in) acpi pad driver.
Move mark_tsc_unstable() out of init to the actual idle invocation path of the pad driver.
There is also another bug/missing_feature in the code that it does not support 'always running apic timer' and switches to broadcast mode unconditionally. Shaohua, can you take a look at that please.
--- drivers/acpi/acpi_pad.c | 13 +++++++++++-- 1 files changed, 11 insertions(+), 2 deletions(-)
drivers/acpi/acpi_pad.c +11 -2
@@ -43,6 +43,10 @@ static DEFINE_MUTEX(isolated_cpus_lock);#define CPUID5_ECX_EXTENSIONS_SUPPORTED (0x1)#define CPUID5_ECX_INTERRUPT_BREAK (0x2)static unsigned long power_saving_mwait_eax; + +static unsigned char tsc_detected_unstable; +static unsigned char tsc_marked_unstable; +static void power_saving_mwait_init (void ) {unsigned int eax, ebx, ecx, edx;
@@ -87,8 +91,8 @@ static void power_saving_mwait_init(void)/*FALL THROUGH*/ default : -/* TSC could halt in idle, so notify users */ - mark_tsc_unstable("TSC halts in idle"); +/* TSC could halt in idle */ + tsc_detected_unstable = 1; }#endif }
@@ -178,6 +182,11 @@ static int power_saving_thread(void *data) expire_time = jiffies +HZ * (100 - idle_pct) /100 ;while (!need_resched ()) { +if (tsc_detected_unstable && !tsc_marked_unstable) { +/* TSC could halt in idle, so notify users */ +mark_tsc_unstable ("TSC halts in idle" ); + tsc_marked_unstable =1 ; + }local_irq_disable (); cpu =smp_processor_id (); clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER,
Signature · 1 line
1.7.0.1
applied
thanks,
Len Brown, Intel Open Source Technology Center