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ACPI: Don't let acpi_pad needlessly mark TSC unstable

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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.

Signed-off-by: Venkatesh Pallipadi <venki@google.com>
Signed-off-by: Len Brown <len.brown@intel.com>
This commit is contained in:
Venkatesh Pallipadi 2010-05-18 14:39:16 -07:00 • committed by Len Brown
commit 0dc698b93f
1 changed files with 11 additions and 2 deletions
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13
drivers/acpi/acpi_pad.c
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@ -43,6 +43,10 @@ static DEFINE_MUTEX(isolated_cpus_lock);
#define CPUID5_ECX_EXTENSIONS_SUPPORTED (0x1) #define CPUID5_ECX_EXTENSIONS_SUPPORTED (0x1)
#define CPUID5_ECX_INTERRUPT_BREAK (0x2) #define CPUID5_ECX_INTERRUPT_BREAK (0x2)
static unsigned long power_saving_mwait_eax; 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) static void power_saving_mwait_init(void)
{ {
unsigned int eax, ebx, ecx, edx; unsigned int eax, ebx, ecx, edx;
@ -87,8 +91,8 @@ static void power_saving_mwait_init(void)
/*FALL THROUGH*/ /*FALL THROUGH*/
default: default:
/* TSC could halt in idle, so notify users */ /* TSC could halt in idle */
mark_tsc_unstable("TSC halts in idle"); tsc_detected_unstable = 1;
} }
#endif #endif
} }
@ -178,6 +182,11 @@ static int power_saving_thread(void *data)
expire_time = jiffies + HZ * (100 - idle_pct) / 100; expire_time = jiffies + HZ * (100 - idle_pct) / 100;
while (!need_resched()) { 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(); local_irq_disable();
cpu = smp_processor_id(); cpu = smp_processor_id();
clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER,