Re: [PATCH] Dynamic tick, version 050127-1
From: Tony Lindgren
Date: Sat Feb 05 2005 - 23:01:51 EST
* Tony Lindgren <tony@xxxxxxxxxxx> [050205 18:39]:
> * Pavel Machek <pavel@xxxxxx> [050205 15:08]:
> >
> > Ok, works slightly better: time no longer runs 2x too fast. When TSC
> > is used, I get same behaviour as before ("sleepy machine"). With
> > "notsc", machine seems to work okay, but I still get 1000 timer
> > interrupts a second.
...
>
> Sounds like your system is not running with the dyn-tick... I'll try
> to fix that TSC bug.
The following patch fixes TSC timer with dyn-tick, and local APIC
timer on UP system with CONFIG_SMP.
Tony
diff -Nru a/arch/i386/Kconfig b/arch/i386/Kconfig
--- a/arch/i386/Kconfig 2005-02-05 19:46:47 -08:00
+++ b/arch/i386/Kconfig 2005-02-05 19:46:47 -08:00
@@ -452,6 +452,16 @@
bool "Provide RTC interrupt"
depends on HPET_TIMER && RTC=y
+config NO_IDLE_HZ
+ bool "Dynamic Tick Timer - Skip timer ticks during idle"
+ help
+ This option enables support for skipping timer ticks when the
+ processor is idle. During system load, timer is continuous.
+ This option saves power, as it allows the system to stay in
+ idle mode longer. Currently supported timers are ACPI PM
+ timer, local APIC timer, and TSC timer. HPET timer is currently
+ not supported.
+
config SMP
bool "Symmetric multi-processing support"
---help---
diff -Nru a/arch/i386/kernel/apic.c b/arch/i386/kernel/apic.c
--- a/arch/i386/kernel/apic.c 2005-02-05 19:46:47 -08:00
+++ b/arch/i386/kernel/apic.c 2005-02-05 19:46:47 -08:00
@@ -26,6 +26,7 @@
#include <linux/mc146818rtc.h>
#include <linux/kernel_stat.h>
#include <linux/sysdev.h>
+#include <linux/dyn-tick-timer.h>
#include <asm/atomic.h>
#include <asm/smp.h>
@@ -909,6 +910,8 @@
#define APIC_DIVISOR 16
+static u32 apic_timer_val;
+
void __setup_APIC_LVTT(unsigned int clocks)
{
unsigned int lvtt_value, tmp_value, ver;
@@ -927,7 +930,15 @@
& ~(APIC_TDR_DIV_1 | APIC_TDR_DIV_TMBASE))
| APIC_TDR_DIV_16);
- apic_write_around(APIC_TMICT, clocks/APIC_DIVISOR);
+ apic_timer_val = clocks/APIC_DIVISOR;
+
+#ifdef CONFIG_NO_IDLE_HZ
+ /* Local APIC timer is 24-bit */
+ if (apic_timer_val)
+ dyn_tick->max_skip = 0xffffff / apic_timer_val;
+#endif
+
+ apic_write_around(APIC_TMICT, apic_timer_val);
}
static void setup_APIC_timer(unsigned int clocks)
@@ -1040,6 +1051,13 @@
*/
setup_APIC_timer(calibration_result);
+#ifdef CONFIG_NO_IDLE_HZ
+ if (calibration_result)
+ dyn_tick->state |= DYN_TICK_USE_APIC;
+ else
+ printk(KERN_INFO "dyn-tick: Cannot use local APIC\n");
+#endif
+
local_irq_enable();
}
@@ -1068,6 +1086,18 @@
}
}
+#if defined(CONFIG_NO_IDLE_HZ)
+void reprogram_apic_timer(unsigned int count)
+{
+ unsigned long flags;
+
+ count *= apic_timer_val;
+ local_irq_save(flags);
+ apic_write_around(APIC_TMICT, count);
+ local_irq_restore(flags);
+}
+#endif
+
/*
* the frequency of the profiling timer can be changed
* by writing a multiplier value into /proc/profile.
@@ -1160,6 +1190,7 @@
fastcall void smp_apic_timer_interrupt(struct pt_regs *regs)
{
+ unsigned long seq;
int cpu = smp_processor_id();
/*
@@ -1178,6 +1209,23 @@
* interrupt lock, which is the WrongThing (tm) to do.
*/
irq_enter();
+
+#ifdef CONFIG_NO_IDLE_HZ
+ /*
+ * Check if we need to wake up PIT interrupt handler.
+ * Otherwise just wake up local APIC timer.
+ */
+ do {
+ seq = read_seqbegin(&xtime_lock);
+ if (dyn_tick->state & (DYN_TICK_ENABLED | DYN_TICK_SKIPPING)) {
+ if (dyn_tick->skip_cpu == cpu && dyn_tick->skip > DYN_TICK_MIN_SKIP)
+ dyn_tick->interrupt(99, NULL, regs);
+ else
+ reprogram_apic_timer(1);
+ }
+ } while (read_seqretry(&xtime_lock, seq));
+#endif
+
smp_local_timer_interrupt(regs);
irq_exit();
}
diff -Nru a/arch/i386/kernel/irq.c b/arch/i386/kernel/irq.c
--- a/arch/i386/kernel/irq.c 2005-02-05 19:46:47 -08:00
+++ b/arch/i386/kernel/irq.c 2005-02-05 19:46:47 -08:00
@@ -15,6 +15,7 @@
#include <linux/seq_file.h>
#include <linux/interrupt.h>
#include <linux/kernel_stat.h>
+#include <linux/dyn-tick-timer.h>
#ifndef CONFIG_X86_LOCAL_APIC
/*
@@ -100,6 +101,11 @@
} else
#endif
__do_IRQ(irq, regs);
+
+#ifdef CONFIG_NO_IDLE_HZ
+ if (dyn_tick->state & (DYN_TICK_ENABLED | DYN_TICK_SKIPPING) && irq != 0)
+ dyn_tick->interrupt(irq, NULL, regs);
+#endif
irq_exit();
diff -Nru a/arch/i386/kernel/time.c b/arch/i386/kernel/time.c
--- a/arch/i386/kernel/time.c 2005-02-05 19:46:47 -08:00
+++ b/arch/i386/kernel/time.c 2005-02-05 19:46:47 -08:00
@@ -46,6 +46,7 @@
#include <linux/bcd.h>
#include <linux/efi.h>
#include <linux/mca.h>
+#include <linux/dyn-tick-timer.h>
#include <asm/io.h>
#include <asm/smp.h>
@@ -301,6 +302,60 @@
return IRQ_HANDLED;
}
+#ifdef CONFIG_NO_IDLE_HZ
+static unsigned long long last_tick;
+void reprogram_pit_tick(int jiffies_to_skip);
+extern void replace_timer_interrupt(void * new_handler);
+
+#if defined(CONFIG_NO_IDLE_HZ) && defined(CONFIG_X86_LOCAL_APIC)
+extern void reprogram_apic_timer(unsigned int count);
+#else
+void reprogram_apic_timer(unsigned int count) {}
+#endif
+
+#ifdef DEBUG
+#define dbg_dyn_tick_irq() {if (skipped && skipped < dyn_tick->skip) \
+ printk("%u/%li ", skipped, dyn_tick->skip);}
+#else
+#define dbg_dyn_tick_irq() {}
+#endif
+
+
+
+/*
+ * This interrupt handler updates the time based on number of jiffies skipped
+ * It would be somewhat more optimized to have a customa handler in each timer
+ * using hardware ticks instead of nanoseconds. Note that CONFIG_NO_IDLE_HZ
+ * currently disables timer fallback on skipped jiffies.
+ */
+irqreturn_t dyn_tick_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
+{
+ unsigned long flags;
+ volatile unsigned long long now;
+ unsigned int skipped = 0;
+ write_seqlock_irqsave(&xtime_lock, flags);
+ now = cur_timer->get_hw_time();
+ while (now - last_tick >= NS_TICK_LEN) {
+ last_tick += NS_TICK_LEN;
+ cur_timer->mark_offset();
+ do_timer_interrupt(irq, NULL, regs);
+ skipped++;
+ }
+ if (dyn_tick->state & (DYN_TICK_ENABLED | DYN_TICK_SKIPPING)) {
+ dbg_dyn_tick_irq();
+ dyn_tick->skip = 1;
+ if (cpu_has_local_apic())
+ reprogram_apic_timer(dyn_tick->skip);
+ reprogram_pit_tick(dyn_tick->skip);
+ dyn_tick->state |= DYN_TICK_ENABLED;
+ dyn_tick->state &= ~DYN_TICK_SKIPPING;
+ }
+ write_sequnlock_irqrestore(&xtime_lock, flags);
+
+ return IRQ_HANDLED;
+}
+#endif
+
/* not static: needed by APM */
unsigned long get_cmos_time(void)
{
@@ -396,6 +451,72 @@
}
#endif
+#ifdef CONFIG_NO_IDLE_HZ
+static struct dyn_tick_timer arch_ltt;
+
+#if defined(CONFIG_X86_UP_APIC) || defined(CONFIG_SMP)
+void disable_pit_tick(void)
+{
+ extern spinlock_t i8253_lock;
+ unsigned long flags;
+ spin_lock_irqsave(&i8253_lock, flags);
+ outb_p(0x31, PIT_MODE); /* binary, mode 1, LSB/MSB, ch 0 */
+ spin_unlock_irqrestore(&i8253_lock, flags);
+}
+#endif
+
+/*
+ * Reprograms the next timer interrupt
+ * PIT timer reprogramming code taken from APM code.
+ * Note that PIT timer is a 16-bit timer, which allows max
+ * skip of only few seconds.
+ */
+void reprogram_pit_tick(int jiffies_to_skip)
+{
+ int skip;
+ extern spinlock_t i8253_lock;
+ unsigned long flags;
+
+ skip = jiffies_to_skip * LATCH;
+ if (skip > 0xffff) {
+ skip = 0xffff;
+ }
+
+ spin_lock_irqsave(&i8253_lock, flags);
+ outb_p(0x34, PIT_MODE); /* binary, mode 2, LSB/MSB, ch 0 */
+ outb_p(skip & 0xff, PIT_CH0); /* LSB */
+ outb(skip >> 8, PIT_CH0); /* MSB */
+ spin_unlock_irqrestore(&i8253_lock, flags);
+}
+
+static int __init dyn_tick_late_init(void)
+{
+ unsigned long flags;
+
+ if (!cur_timer->get_hw_time)
+ return -ENODEV;
+ write_seqlock_irqsave(&xtime_lock, flags);
+ last_tick = cur_timer->get_hw_time();
+ dyn_tick->skip = 1;
+ if (!cpu_has_local_apic())
+ dyn_tick->max_skip = 0xffff/LATCH; /* PIT timer length */
+ printk(KERN_INFO "dyn-tick: Maximum ticks to skip limited to %i\n",
+ dyn_tick->max_skip);
+ write_sequnlock_irqrestore(&xtime_lock, flags);
+
+ if (cur_timer->late_init)
+ cur_timer->late_init();
+ dyn_tick->interrupt = dyn_tick_timer_interrupt;
+ replace_timer_interrupt(dyn_tick->interrupt);
+
+ write_seqlock_irqsave(&xtime_lock, flags);
+ dyn_tick->state |= DYN_TICK_ENABLED;
+ write_sequnlock_irqrestore(&xtime_lock, flags);
+
+ return 0;
+}
+#endif
+
void __init time_init(void)
{
#ifdef CONFIG_HPET_TIMER
@@ -415,6 +536,16 @@
cur_timer = select_timer();
printk(KERN_INFO "Using %s for high-res timesource\n",cur_timer->name);
+
+#ifdef CONFIG_NO_IDLE_HZ
+ if (strncmp(cur_timer->name, "tsc", 3) == 0 ||
+ strncmp(cur_timer->name, "pmtmr", 3) == 0) {
+ arch_ltt.init = dyn_tick_late_init;
+ dyn_tick_register(&arch_ltt);
+ } else
+ printk(KERN_INFO "dyn-tick: Cannot use timer %s\n",
+ cur_timer->name);
+#endif
time_init_hook();
}
diff -Nru a/arch/i386/kernel/timers/timer_pm.c b/arch/i386/kernel/timers/timer_pm.c
--- a/arch/i386/kernel/timers/timer_pm.c 2005-02-05 19:46:47 -08:00
+++ b/arch/i386/kernel/timers/timer_pm.c 2005-02-05 19:46:47 -08:00
@@ -15,6 +15,7 @@
#include <linux/module.h>
#include <linux/device.h>
#include <linux/init.h>
+#include <linux/dyn-tick-timer.h>
#include <asm/types.h>
#include <asm/timer.h>
#include <asm/smp.h>
@@ -168,6 +169,7 @@
monotonic_base += delta * NSEC_PER_USEC;
write_sequnlock(&monotonic_lock);
+#ifndef CONFIG_NO_IDLE_HZ
/* convert to ticks */
delta += offset_delay;
lost = delta / (USEC_PER_SEC / HZ);
@@ -184,6 +186,7 @@
first_run = 0;
offset_delay = 0;
}
+#endif
}
@@ -238,6 +241,25 @@
return (unsigned long) offset_delay + cyc2us(delta);
}
+static unsigned long long ns_time;
+
+static unsigned long long get_hw_time_pmtmr(void)
+{
+ u32 now, delta;
+ static unsigned int last_cycles;
+ now = read_pmtmr();
+ delta = (now - last_cycles) & ACPI_PM_MASK;
+ last_cycles = now;
+ ns_time += cyc2us(delta) * NSEC_PER_USEC;
+ return ns_time;
+}
+
+static void late_init_pmtmr(void)
+{
+ ns_time = monotonic_clock_pmtmr();
+}
+
+extern irqreturn_t pmtmr_interrupt(int irq, void *dev_id, struct pt_regs *regs);
/* acpi timer_opts struct */
static struct timer_opts timer_pmtmr = {
@@ -245,7 +267,9 @@
.mark_offset = mark_offset_pmtmr,
.get_offset = get_offset_pmtmr,
.monotonic_clock = monotonic_clock_pmtmr,
+ .get_hw_time = get_hw_time_pmtmr,
.delay = delay_pmtmr,
+ .late_init = late_init_pmtmr,
};
struct init_timer_opts __initdata timer_pmtmr_init = {
diff -Nru a/arch/i386/kernel/timers/timer_tsc.c b/arch/i386/kernel/timers/timer_tsc.c
--- a/arch/i386/kernel/timers/timer_tsc.c 2005-02-05 19:46:47 -08:00
+++ b/arch/i386/kernel/timers/timer_tsc.c 2005-02-05 19:46:47 -08:00
@@ -112,6 +112,15 @@
return delay_at_last_interrupt + edx;
}
+static unsigned long get_hw_time_tsc(void)
+{
+ register unsigned long eax, edx;
+
+ unsigned long long hw_time;
+ rdtscll(hw_time);
+ return cycles_2_ns(hw_time);
+}
+
static unsigned long long monotonic_clock_tsc(void)
{
unsigned long long last_offset, this_offset, base;
@@ -348,6 +357,7 @@
rdtsc(last_tsc_low, last_tsc_high);
+#ifndef CONFIG_NO_IDLE_HZ
spin_lock(&i8253_lock);
outb_p(0x00, PIT_MODE); /* latch the count ASAP */
@@ -415,11 +425,14 @@
cpufreq_delayed_get();
} else
lost_count = 0;
+#endif
+
/* update the monotonic base value */
this_offset = ((unsigned long long)last_tsc_high<<32)|last_tsc_low;
monotonic_base += cycles_2_ns(this_offset - last_offset);
write_sequnlock(&monotonic_lock);
+#ifndef CONFIG_NO_IDLE_HZ
/* calculate delay_at_last_interrupt */
count = ((LATCH-1) - count) * TICK_SIZE;
delay_at_last_interrupt = (count + LATCH/2) / LATCH;
@@ -430,6 +443,7 @@
*/
if (lost && abs(delay - delay_at_last_interrupt) > (900000/HZ))
jiffies_64++;
+#endif
}
static int __init init_tsc(char* override)
@@ -551,6 +565,7 @@
.mark_offset = mark_offset_tsc,
.get_offset = get_offset_tsc,
.monotonic_clock = monotonic_clock_tsc,
+ .get_hw_time = get_hw_time_tsc,
.delay = delay_tsc,
};
diff -Nru a/arch/i386/mach-default/setup.c b/arch/i386/mach-default/setup.c
--- a/arch/i386/mach-default/setup.c 2005-02-05 19:46:47 -08:00
+++ b/arch/i386/mach-default/setup.c 2005-02-05 19:46:47 -08:00
@@ -85,6 +85,22 @@
setup_irq(0, &irq0);
}
+/**
+ * replace_timer_interrupt - allow replacing timer interrupt handler
+ *
+ * Description:
+ * Can be used to replace timer interrupt handler with a more optimized
+ * handler. Used for enabling and disabling of CONFIG_NO_IDLE_HZ.
+ */
+void replace_timer_interrupt(void * new_handler)
+{
+ unsigned long flags;
+
+ write_seqlock_irqsave(&xtime_lock, flags);
+ irq0.handler = new_handler;
+ write_sequnlock_irqrestore(&xtime_lock, flags);
+}
+
#ifdef CONFIG_MCA
/**
* mca_nmi_hook - hook into MCA specific NMI chain
diff -Nru a/include/asm-i386/timer.h b/include/asm-i386/timer.h
--- a/include/asm-i386/timer.h 2005-02-05 19:46:47 -08:00
+++ b/include/asm-i386/timer.h 2005-02-05 19:46:47 -08:00
@@ -1,6 +1,7 @@
#ifndef _ASMi386_TIMER_H
#define _ASMi386_TIMER_H
#include <linux/init.h>
+#include <linux/interrupt.h>
/**
* struct timer_ops - used to define a timer source
@@ -21,7 +22,9 @@
void (*mark_offset)(void);
unsigned long (*get_offset)(void);
unsigned long long (*monotonic_clock)(void);
+ unsigned long long (*get_hw_time)(void);
void (*delay)(unsigned long);
+ void (*late_init)(void);
};
struct init_timer_opts {
diff -Nru a/include/linux/dyn-tick-timer.h b/include/linux/dyn-tick-timer.h
--- /dev/null Wed Dec 31 16:00:00 196900
+++ b/include/linux/dyn-tick-timer.h 2005-02-05 19:46:47 -08:00
@@ -0,0 +1,71 @@
+/*
+ * linux/include/linux/dyn-tick-timer.h
+ *
+ * Copyright (C) 2004 Nokia Corporation
+ * Written by Tony Lindgen <tony@xxxxxxxxxxx> and
+ * Tuukka Tikkanen <tuukka.tikkanen@xxxxxxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN
+ * NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <linux/interrupt.h>
+
+#define DYN_TICK_USE_APIC (1 << 2)
+#define DYN_TICK_SKIPPING (1 << 1)
+#define DYN_TICK_ENABLED (1 << 0)
+
+struct dyn_tick_state {
+ unsigned int state; /* Current state */
+ int skip_cpu; /* Skip handling processor */
+ unsigned long skip; /* Ticks to skip */
+ unsigned int max_skip; /* Max number of ticks to skip */
+ unsigned long irq_skip_mask; /* Do not update time from these irqs */
+ irqreturn_t (*interrupt)(int, void *, struct pt_regs *);
+};
+
+/* REVISIT: Add functions to enable/disable dyn-tick on the fly */
+struct dyn_tick_timer {
+ int (*init) (void);
+};
+
+extern struct dyn_tick_state * dyn_tick;
+extern void dyn_tick_register(struct dyn_tick_timer * new_timer);
+
+#define NS_TICK_LEN ((1 * 1000000000)/HZ)
+#define DYN_TICK_MIN_SKIP 2
+
+#if defined(CONFIG_SMP) || defined(CONFIG_X86_UP_APIC)
+#define cpu_has_local_apic() (dyn_tick->state & DYN_TICK_USE_APIC)
+#else
+#define cpu_has_local_apic() 0
+#endif
+
+#ifdef CONFIG_NO_IDLE_HZ
+
+#if defined(CONFIG_X86) || defined(CONFIG_IA64) || defined(CONFIG_X86_64)
+#define arch_has_safe_halt() 1
+#endif
+
+#else
+
+#define arch_has_safe_halt() 0
+
+#endif
diff -Nru a/kernel/Makefile b/kernel/Makefile
--- a/kernel/Makefile 2005-02-05 19:46:47 -08:00
+++ b/kernel/Makefile 2005-02-05 19:46:47 -08:00
@@ -26,6 +26,7 @@
obj-$(CONFIG_KPROBES) += kprobes.o
obj-$(CONFIG_SYSFS) += ksysfs.o
obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
+obj-$(CONFIG_NO_IDLE_HZ) += dyn-tick-timer.o
ifneq ($(CONFIG_IA64),y)
# According to Alan Modra <alan@xxxxxxxxxxxxxxxx>, the -fno-omit-frame-pointer is
diff -Nru a/kernel/dyn-tick-timer.c b/kernel/dyn-tick-timer.c
--- /dev/null Wed Dec 31 16:00:00 196900
+++ b/kernel/dyn-tick-timer.c 2005-02-05 19:46:47 -08:00
@@ -0,0 +1,149 @@
+/*
+ * linux/arch/i386/kernel/dyn-tick.c
+ *
+ * Beginnings of generic dynamic tick timer support
+ *
+ * Copyright (C) 2004 Nokia Corporation
+ * Written by Tony Lindgen <tony@xxxxxxxxxxx> and
+ * Tuukka Tikkanen <tuukka.tikkanen@xxxxxxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN
+ * NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ *
+ * TODO:
+ * - Add functions for enabling/disabling dyn-tick on the fly
+ * - Generalize to work with ARM sys_timer
+ */
+
+#include <linux/version.h>
+#include <linux/config.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/cpumask.h>
+#include <linux/pm.h>
+#include <linux/dyn-tick-timer.h>
+#include <asm/io.h>
+
+#include "io_ports.h"
+
+#define VERSION 050205-1
+
+struct dyn_tick_state dyn_tick_state;
+struct dyn_tick_state * dyn_tick = &dyn_tick_state;
+struct dyn_tick_timer dyn_tick_timer;
+struct dyn_tick_timer * dyn_tick_cfg = &dyn_tick_timer;
+static void (*orig_idle) (void) = 0;
+extern void disable_pit_tick(void);
+extern void reprogram_pit_tick(int jiffies_to_skip);
+extern void reprogram_apic_timer(unsigned int count);
+extern void reprogram_pit_tick(int jiffies_to_skip);
+static cpumask_t dyn_cpu_map;
+
+/*
+ * We want to have all processors idle before reprogramming the next
+ * timer interrupt. Note that we must maintain the state for dynamic tick,
+ * otherwise the idle loop could be reprogramming the timer continuously
+ * further into the future, and the timer interrupt would never happen.
+ */
+static void dyn_tick_idle(void)
+{
+ int cpu;
+ unsigned long flags;
+ cpumask_t idle_cpus;
+ unsigned long next;
+
+ if (!(dyn_tick->state & DYN_TICK_ENABLED))
+ goto out;
+
+ /* Check if we are already skipping ticks and can idle other cpus */
+ if (dyn_tick->state & DYN_TICK_SKIPPING) {
+ reprogram_apic_timer(dyn_tick->skip);
+ goto out;
+ }
+
+ /* Check if we can start skipping ticks */
+ write_seqlock_irqsave(&xtime_lock, flags);
+ cpu = smp_processor_id();
+ cpu_set(cpu, dyn_cpu_map);
+ cpus_and(idle_cpus, dyn_cpu_map, cpu_online_map);
+ if (cpus_equal(idle_cpus, cpu_online_map)) {
+ next = next_timer_interrupt();
+ if (jiffies > next) {
+ //printk("Too late? next: %lu jiffies: %lu\n",
+ // next, jjiffies);
+ dyn_tick->skip = 1;
+ } else
+ dyn_tick->skip = next_timer_interrupt() - jiffies;
+ if (dyn_tick->skip > DYN_TICK_MIN_SKIP) {
+ if (dyn_tick->skip > dyn_tick->max_skip)
+ dyn_tick->skip = dyn_tick->max_skip;
+ if (cpu_has_local_apic()) {
+ disable_pit_tick();
+ reprogram_apic_timer(dyn_tick->skip);
+ } else
+ reprogram_pit_tick(dyn_tick->skip);
+ dyn_tick->skip_cpu = cpu;
+ dyn_tick->state |= DYN_TICK_SKIPPING;
+ }
+ cpus_clear(dyn_cpu_map);
+ }
+ write_sequnlock_irqrestore(&xtime_lock, flags);
+
+out:
+ if (orig_idle)
+ orig_idle();
+ else if (arch_has_safe_halt())
+ safe_halt();
+}
+
+void __init dyn_tick_register(struct dyn_tick_timer * new_timer)
+{
+ dyn_tick_cfg->init = new_timer->init;
+ printk(KERN_INFO "dyn-tick: Registering dynamic tick timer\n");
+}
+
+/*
+ * We need to initialize dynamic tick after calibrate delay
+ */
+static int __init dyn_tick_init(void)
+{
+ int ret = 0;
+
+ if (dyn_tick_cfg->init == NULL)
+ return -ENODEV;
+
+ ret = dyn_tick_cfg->init();
+ if (ret != 0) {
+ printk(KERN_WARNING "dyn-tick: Init failed\n");
+ return -ENODEV;
+ }
+ orig_idle = pm_idle;
+ pm_idle = dyn_tick_idle;
+#if (LINUX_VERSION_CODE > KERNEL_VERSION(2,6,10))
+ cpu_idle_wait();
+#endif
+ printk(KERN_INFO "dyn-tick: Timer using dynamic tick\n");
+
+ return ret;
+}
+late_initcall(dyn_tick_init);