Revert "ACPI: Only use IPI on known broken machines (AMD, Dothan/BaniasPentium M)"

This reverts commit 25496cae, which
broke bootup on at least Ingo's ThinkPad T60.  Need to figure out
exactly what is wrong before we can re-do the logic.
Requested-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Thomas Renninger <trenn@suse.de>
Cc: Len Brown <len.brown@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/acpi/processor_idle.c

@@ -89,12 +89,6 @@ module_param(nocst, uint, 0000);
 static unsigned int bm_history __read_mostly =
     (HZ >= 800 ? 0xFFFFFFFF : ((1U << (HZ / 25)) - 1));
 module_param(bm_history, uint, 0644);
-
-static unsigned use_ipi = 2;
-module_param(use_ipi, uint, 0644);
-MODULE_PARM_DESC(use_ipi, "IPI (vs. LAPIC) irqs for not waking up from C2/C3"
-		 " machines. 0=apic, 1=ipi, 2=auto\n");
-
 /* --------------------------------------------------------------------------
                                 Power Management
    -------------------------------------------------------------------------- */
@@ -266,8 +260,9 @@ static void acpi_cstate_enter(struct acpi_processor_cx *cstate)
 
 /*
  * Some BIOS implementations switch to C3 in the published C2 state.
- * This seems to be a common problem on AMD boxen and Intel Dothan/Banias
- * Pentium M machines.
+ * This seems to be a common problem on AMD boxen, but other vendors
+ * are affected too. We pick the most conservative approach: we assume
+ * that the local APIC stops in both C2 and C3.
  */
 static void acpi_timer_check_state(int state, struct acpi_processor *pr,
 				   struct acpi_processor_cx *cx)
@@ -281,17 +276,8 @@ static void acpi_timer_check_state(int state, struct acpi_processor *pr,
 	if (pwr->timer_broadcast_on_state < state)
 		return;
 
-	if (cx->type >= ACPI_STATE_C2) {
-		if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
-			pr->power.timer_broadcast_on_state = state;
-		else if ((boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
-			  boot_cpu_data.x86 == 6) &&
-			 (boot_cpu_data.x86_model == 13 ||
-			  boot_cpu_data.x86_model == 9))
-		{
+	if (cx->type >= ACPI_STATE_C2)
 		pr->power.timer_broadcast_on_state = state;
-		}
-	}
 }
 
 static void acpi_propagate_timer_broadcast(struct acpi_processor *pr)
@@ -306,16 +292,10 @@ static void acpi_propagate_timer_broadcast(struct acpi_processor *pr)
 #else
 	cpumask_t mask = cpumask_of_cpu(pr->id);
 
-	if (use_ipi == 0)
-		on_each_cpu(switch_APIC_timer_to_ipi, &mask, 1, 1);
-	else if (use_ipi == 1)
-		on_each_cpu(switch_ipi_to_APIC_timer, &mask, 1, 1);
-	else {
 	if (pr->power.timer_broadcast_on_state < INT_MAX)
 		on_each_cpu(switch_APIC_timer_to_ipi, &mask, 1, 1);
 	else
 		on_each_cpu(switch_ipi_to_APIC_timer, &mask, 1, 1);
-	}
 #endif
 }
 
@@ -1033,13 +1013,13 @@ static int acpi_processor_power_verify(struct acpi_processor *pr)
 
 		case ACPI_STATE_C2:
 			acpi_processor_power_verify_c2(cx);
-			if (cx->valid && use_ipi != 0 && use_ipi != 1)
+			if (cx->valid)
 				acpi_timer_check_state(i, pr, cx);
 			break;
 
 		case ACPI_STATE_C3:
 			acpi_processor_power_verify_c3(pr, cx);
-			if (cx->valid && use_ipi != 0 && use_ipi != 1)
+			if (cx->valid)
 				acpi_timer_check_state(i, pr, cx);
 			break;
 		}