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Commit 0dc698b9 authored by Venkatesh Pallipadi's avatar Venkatesh Pallipadi Committed by Len Brown
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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.

Signed-off-by: default avatarVenkatesh Pallipadi <venki@google.com>
Signed-off-by: default avatarLen Brown <len.brown@intel.com>
parent b6fecaa8

drivers/acpi/acpi_pad.c

+11 −2
Original line number Original line Diff line number Diff line
@@ -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,