ACPI: Don't let acpi_pad needlessly mark TSC unstable (0dc698b9) · Commits · 戴 / test

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>

drivers/acpi/acpi_pad.c

+11 −2

Original line number	Diff line number	Diff line
		@@ -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,

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