Whenever we see that a CPU is capable of C3 (during ACPI cstate init), we
disable local APIC timer and switch to using a broadcast from external timer
interrupt (IRQ 0).
Patch below adds the code for x86_64.
Signed-off-by: Venkatesh Pallipadi <[email protected]>
Index: linux-2.6.14/arch/x86_64/kernel/apic.c
===================================================================
--- linux-2.6.14.orig/arch/x86_64/kernel/apic.c 2005-12-05 15:15:28.000000000 -0800
+++ linux-2.6.14/arch/x86_64/kernel/apic.c 2005-12-12 14:34:28.427171400 -0800
@@ -25,6 +25,7 @@
#include <linux/mc146818rtc.h>
#include <linux/kernel_stat.h>
#include <linux/sysdev.h>
+#include <linux/module.h>
#include <asm/atomic.h>
#include <asm/smp.h>
@@ -38,6 +39,12 @@
int disable_apic_timer __initdata;
+/*
+ * cpu_mask that denotes the CPUs that needs timer interrupt coming in as
+ * IPIs in place of local APIC timers
+ */
+static cpumask_t timer_interrupt_broadcast_ipi_mask;
+
/* Using APIC to generate smp_local_timer_interrupt? */
int using_apic_timer = 0;
@@ -656,9 +663,14 @@
static void __setup_APIC_LVTT(unsigned int clocks)
{
unsigned int lvtt_value, tmp_value, ver;
+ int cpu = smp_processor_id();
ver = GET_APIC_VERSION(apic_read(APIC_LVR));
lvtt_value = APIC_LVT_TIMER_PERIODIC | LOCAL_TIMER_VECTOR;
+
+ if (cpu_isset(cpu, timer_interrupt_broadcast_ipi_mask))
+ apic_write_around(APIC_LVTT, lvtt_value | APIC_LVT_MASKED);
+
apic_write_around(APIC_LVTT, lvtt_value);
/*
@@ -781,7 +793,7 @@
local_irq_enable();
}
-void __cpuinit disable_APIC_timer(void)
+void disable_APIC_timer(void)
{
if (using_apic_timer) {
unsigned long v;
@@ -793,7 +805,10 @@
void enable_APIC_timer(void)
{
- if (using_apic_timer) {
+ int cpu = smp_processor_id();
+
+ if (using_apic_timer &&
+ !cpu_isset(cpu, timer_interrupt_broadcast_ipi_mask)) {
unsigned long v;
v = apic_read(APIC_LVTT);
@@ -801,6 +816,42 @@
}
}
+void switch_APIC_timer_to_ipi(void *cpumask)
+{
+ cpumask_t mask = *(cpumask_t *)cpumask;
+ int cpu = smp_processor_id();
+
+ if (cpu_isset(cpu, mask) &&
+ !cpu_isset(cpu, timer_interrupt_broadcast_ipi_mask)) {
+ disable_APIC_timer();
+ cpu_set(cpu, timer_interrupt_broadcast_ipi_mask);
+ }
+}
+EXPORT_SYMBOL(switch_APIC_timer_to_ipi);
+
+void smp_send_timer_broadcast_ipi(void)
+{
+ cpumask_t mask;
+
+ cpus_and(mask, cpu_online_map, timer_interrupt_broadcast_ipi_mask);
+ if (!cpus_empty(mask)) {
+ send_IPI_mask(mask, LOCAL_TIMER_VECTOR);
+ }
+}
+
+void switch_ipi_to_APIC_timer(void *cpumask)
+{
+ cpumask_t mask = *(cpumask_t *)cpumask;
+ int cpu = smp_processor_id();
+
+ if (cpu_isset(cpu, mask) &&
+ cpu_isset(cpu, timer_interrupt_broadcast_ipi_mask)) {
+ cpu_clear(cpu, timer_interrupt_broadcast_ipi_mask);
+ enable_APIC_timer();
+ }
+}
+EXPORT_SYMBOL(switch_ipi_to_APIC_timer);
+
int setup_profiling_timer(unsigned int multiplier)
{
return -EINVAL;
Index: linux-2.6.14/include/asm-x86_64/apic.h
===================================================================
--- linux-2.6.14.orig/include/asm-x86_64/apic.h 2005-12-05 16:24:35.000000000 -0800
+++ linux-2.6.14/include/asm-x86_64/apic.h 2005-12-05 16:27:36.000000000 -0800
@@ -113,6 +113,12 @@
extern void setup_threshold_lvt(unsigned long lvt_off);
+void smp_send_timer_broadcast_ipi(void);
+void switch_APIC_timer_to_ipi(void *cpumask);
+void switch_ipi_to_APIC_timer(void *cpumask);
+
+#define ARCH_APICTIMER_STOPS_ON_C3 1
+
#endif /* CONFIG_X86_LOCAL_APIC */
extern unsigned boot_cpu_id;
Index: linux-2.6.14/arch/x86_64/kernel/time.c
===================================================================
--- linux-2.6.14.orig/arch/x86_64/kernel/time.c 2005-12-01 18:04:25.000000000 -0800
+++ linux-2.6.14/arch/x86_64/kernel/time.c 2005-12-05 16:26:37.000000000 -0800
@@ -476,6 +476,11 @@
write_sequnlock(&xtime_lock);
+#ifdef CONFIG_X86_LOCAL_APIC
+ if (using_apic_timer)
+ smp_send_timer_broadcast_ipi();
+#endif
+
return IRQ_HANDLED;
}
-
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