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Subject[patch 15/21] clockevents: drivers for i386
From: Thomas Gleixner <tglx@linutronix.de>

Add clockevent drivers for i386: lapic (local) and PIT (global).
Update the timer IRQ to call into the PIT driver's event handler
and the lapic-timer IRQ to call into the lapic clockevent driver.
The assignement of timer functionality is delegated to the core
framework code and replaces the compile and runtime evalution in
do_timer_interrupt_hook()

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
--
arch/i386/Kconfig | 4 +
arch/i386/kernel/apic.c | 117 ++++++++++++++++++++++++++-----
arch/i386/kernel/i8253.c | 94 ++++++++++++++++++++++--
arch/i386/kernel/time.c | 45 -----------
include/asm-i386/i8253.h | 18 ++++
include/asm-i386/mach-default/do_timer.h | 27 +------
include/asm-i386/mach-visws/do_timer.h | 2
include/asm-i386/mach-voyager/do_timer.h | 15 ++-
8 files changed, 225 insertions(+), 97 deletions(-)
Index: linux-2.6.18-mm2/arch/i386/Kconfig
===================================================================
--- linux-2.6.18-mm2.orig/arch/i386/Kconfig 2006-10-02 00:55:46.000000000 +0200
+++ linux-2.6.18-mm2/arch/i386/Kconfig 2006-10-02 00:55:53.000000000 +0200
@@ -18,6 +18,10 @@ config GENERIC_TIME
bool
default y

+config GENERIC_CLOCKEVENTS
+ bool
+ default y
+
config LOCKDEP_SUPPORT
bool
default y
Index: linux-2.6.18-mm2/arch/i386/kernel/apic.c
===================================================================
--- linux-2.6.18-mm2.orig/arch/i386/kernel/apic.c 2006-10-02 00:55:46.000000000 +0200
+++ linux-2.6.18-mm2/arch/i386/kernel/apic.c 2006-10-02 00:55:53.000000000 +0200
@@ -25,6 +25,7 @@
#include <linux/kernel_stat.h>
#include <linux/sysdev.h>
#include <linux/cpu.h>
+#include <linux/clockchips.h>
#include <linux/module.h>

#include <asm/atomic.h>
@@ -70,6 +71,25 @@ static inline void lapic_enable(void)
*/
int apic_verbosity;

+static unsigned int calibration_result;
+
+static void lapic_next_event(unsigned long delta,
+ struct clock_event_device *evt);
+static void lapic_timer_setup(enum clock_event_mode mode,
+ struct clock_event_device *evt);
+
+/*
+ * The local apic timer can be used for any function which is CPU local.
+ */
+static struct clock_event_device lapic_clockevent = {
+ .name = "lapic",
+ .capabilities = CLOCK_CAP_NEXTEVT | CLOCK_CAP_PROFILE
+ | CLOCK_CAP_UPDATE,
+ .shift = 32,
+ .set_mode = lapic_timer_setup,
+ .set_next_event = lapic_next_event,
+};
+static DEFINE_PER_CPU(struct clock_event_device, lapic_events);

static void apic_pm_activate(void);

@@ -919,6 +939,11 @@ fake_ioapic_page:
*/

/*
+ * FIXME: Move this to i8253.h. There is no need to keep the access to
+ * the PIT scattered all around the place -tglx
+ */
+
+/*
* The timer chip is already set up at HZ interrupts per second here,
* but we do not accept timer interrupts yet. We only allow the BP
* to calibrate.
@@ -976,13 +1001,15 @@ void (*wait_timer_tick)(void) __devinitd

#define APIC_DIVISOR 16

-static void __setup_APIC_LVTT(unsigned int clocks)
+static void __setup_APIC_LVTT(unsigned int clocks, int oneshot)
{
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;
+ lvtt_value = LOCAL_TIMER_VECTOR;
+ if (!oneshot)
+ lvtt_value |= APIC_LVT_TIMER_PERIODIC;
if (!APIC_INTEGRATED(ver))
lvtt_value |= SET_APIC_TIMER_BASE(APIC_TIMER_BASE_DIV);

@@ -999,23 +1026,43 @@ static void __setup_APIC_LVTT(unsigned i
& ~(APIC_TDR_DIV_1 | APIC_TDR_DIV_TMBASE))
| APIC_TDR_DIV_16);

- apic_write_around(APIC_TMICT, clocks/APIC_DIVISOR);
+ if (!oneshot)
+ apic_write_around(APIC_TMICT, clocks/APIC_DIVISOR);
}

-static void __devinit setup_APIC_timer(unsigned int clocks)
+static void lapic_next_event(unsigned long delta,
+ struct clock_event_device *evt)
+{
+ apic_write_around(APIC_TMICT, delta);
+}
+
+static void lapic_timer_setup(enum clock_event_mode mode,
+ struct clock_event_device *evt)
{
unsigned long flags;

local_irq_save(flags);
+ if (CLOCK_EVT_PERIODIC) {
+ /*
+ * Wait for IRQ0's slice:
+ */
+ wait_timer_tick();
+ }
+ __setup_APIC_LVTT(calibration_result, mode != CLOCK_EVT_PERIODIC);
+ local_irq_restore(flags);
+}

- /*
- * Wait for IRQ0's slice:
- */
- wait_timer_tick();
+/*
+ * Setup the local APIC timer for this CPU. Copy the initilized values
+ * of the boot CPU and register the clock event in the framework.
+ */
+static void __devinit setup_APIC_timer(void)
+{
+ struct clock_event_device *levt = &__get_cpu_var(lapic_events);

- __setup_APIC_LVTT(clocks);
+ memcpy(levt, &lapic_clockevent, sizeof(*levt));

- local_irq_restore(flags);
+ register_local_clockevent(levt);
}

/*
@@ -1024,6 +1071,8 @@ static void __devinit setup_APIC_timer(u
* to calibrate, since some later bootup code depends on getting
* the first irq? Ugh.
*
+ * TODO: Fix this rather than saying "Ugh" -tglx
+ *
* We want to do the calibration only once since we
* want to have local timer irqs syncron. CPUs connected
* by the same APIC bus have the very same bus frequency.
@@ -1046,7 +1095,7 @@ static int __init calibrate_APIC_clock(v
* value into the APIC clock, we just want to get the
* counter running for calibration.
*/
- __setup_APIC_LVTT(1000000000);
+ __setup_APIC_LVTT(1000000000, 0);

/*
* The timer chip counts down to zero. Let's wait
@@ -1083,6 +1132,14 @@ static int __init calibrate_APIC_clock(v

result = (tt1-tt2)*APIC_DIVISOR/LOOPS;

+ /* Calculate the scaled math multiplication factor */
+ lapic_clockevent.mult = div_sc(tt1-tt2, TICK_NSEC * LOOPS, 32);
+ lapic_clockevent.max_delta_ns =
+ clockevent_delta2ns(0x7FFFFF, &lapic_clockevent);
+ printk("lapic max_delta_ns: %ld\n", lapic_clockevent.max_delta_ns);
+ lapic_clockevent.min_delta_ns =
+ clockevent_delta2ns(0xF, &lapic_clockevent);
+
if (cpu_has_tsc)
apic_printk(APIC_VERBOSE, "..... CPU clock speed is "
"%ld.%04ld MHz.\n",
@@ -1097,8 +1154,6 @@ static int __init calibrate_APIC_clock(v
return result;
}

-static unsigned int calibration_result;
-
void __init setup_boot_APIC_clock(void)
{
unsigned long flags;
@@ -1111,14 +1166,14 @@ void __init setup_boot_APIC_clock(void)
/*
* Now set up the timer for real.
*/
- setup_APIC_timer(calibration_result);
+ setup_APIC_timer();

local_irq_restore(flags);
}

void __devinit setup_secondary_APIC_clock(void)
{
- setup_APIC_timer(calibration_result);
+ setup_APIC_timer();
}

void disable_APIC_timer(void)
@@ -1164,6 +1219,35 @@ void switch_APIC_timer_to_ipi(void *cpum
!cpu_isset(cpu, timer_bcast_ipi)) {
disable_APIC_timer();
cpu_set(cpu, timer_bcast_ipi);
+#ifdef CONFIG_HIGH_RES_TIMERS
+ /*
+ * C3 stops the local apic timer. We can not make high
+ * resolution timers and dynamic ticks work with one global
+ * timer. Disable the NEXTEVT capability, so high resolution /
+ * dyntick mode gets disabled too.
+ *
+ * There is a solution for this problem, but this is beyond the
+ * scope of this initial patchset:
+ *
+ * When the local apic timer is unusable in C3, then we can
+ * utilize the PIT to provide a global wakeup, which can be
+ * directed to the CPU which has the earliest wakeup
+ * point. Once the CPU is up again, the local apic is resumed
+ * and can be used for the per cpu clock events again. It's not
+ * hard to provide the infrastructure, but I need more insight
+ * into the ACPI code to get it right.
+ *
+ * Disable the highres/dyntick feature in this case for now,
+ * until somebody beats the ACPI clue into me. :)
+ *
+ * tglx
+ */
+ printk("Disabling NO_HZ and high resolution timers "
+ "due to timer broadcasting (C3 stops local apic)\n");
+ for_each_possible_cpu(cpu)
+ per_cpu(lapic_events, cpu).capabilities &=
+ ~CLOCK_CAP_NEXTEVT;
+#endif
}
}
EXPORT_SYMBOL(switch_APIC_timer_to_ipi);
@@ -1224,6 +1308,7 @@ inline void smp_local_timer_interrupt(st
fastcall void smp_apic_timer_interrupt(struct pt_regs *regs)
{
int cpu = smp_processor_id();
+ struct clock_event_device *evt = &per_cpu(lapic_events, cpu);

/*
* the NMI deadlock-detector uses this.
@@ -1241,7 +1326,7 @@ fastcall void smp_apic_timer_interrupt(s
* interrupt lock, which is the WrongThing (tm) to do.
*/
irq_enter();
- smp_local_timer_interrupt(regs);
+ evt->event_handler(regs);
irq_exit();
}

Index: linux-2.6.18-mm2/arch/i386/kernel/i8253.c
===================================================================
--- linux-2.6.18-mm2.orig/arch/i386/kernel/i8253.c 2006-10-02 00:55:46.000000000 +0200
+++ linux-2.6.18-mm2/arch/i386/kernel/i8253.c 2006-10-02 00:55:53.000000000 +0200
@@ -2,7 +2,7 @@
* i8253.c 8253/PIT functions
*
*/
-#include <linux/clocksource.h>
+#include <linux/clockchips.h>
#include <linux/spinlock.h>
#include <linux/jiffies.h>
#include <linux/sysdev.h>
@@ -19,20 +19,98 @@
DEFINE_SPINLOCK(i8253_lock);
EXPORT_SYMBOL(i8253_lock);

-void setup_pit_timer(void)
+#ifdef CONFIG_HPET_TIMER
+/*
+ * HPET replaces the PIT, when enabled. So we need to know, which of
+ * the two timers is used
+ */
+struct clock_event_device *global_clock_event;
+#endif
+
+/*
+ * Initialize the PIT timer.
+ *
+ * This is also called after resume to bring the PIT into operation again.
+ */
+static void init_pit_timer(enum clock_event_mode mode,
+ struct clock_event_device *evt)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&i8253_lock, flags);
+
+ switch(mode) {
+ case CLOCK_EVT_PERIODIC:
+ /* binary, mode 2, LSB/MSB, ch 0 */
+ outb_p(0x34, PIT_MODE);
+ udelay(10);
+ outb_p(LATCH & 0xff , PIT_CH0); /* LSB */
+ outb(LATCH >> 8 , PIT_CH0); /* MSB */
+ break;
+
+ case CLOCK_EVT_ONESHOT:
+ case CLOCK_EVT_SHUTDOWN:
+ /* One shot setup */
+ outb_p(0x38, PIT_MODE);
+ udelay(10);
+ break;
+ }
+ spin_unlock_irqrestore(&i8253_lock, flags);
+}
+
+/*
+ * Program the next event in oneshot mode
+ *
+ * Delta is given in PIT ticks
+ */
+static void pit_next_event(unsigned long delta, struct clock_event_device *evt)
{
unsigned long flags;

spin_lock_irqsave(&i8253_lock, flags);
- outb_p(0x34,PIT_MODE); /* binary, mode 2, LSB/MSB, ch 0 */
- udelay(10);
- outb_p(LATCH & 0xff , PIT_CH0); /* LSB */
- udelay(10);
- outb(LATCH >> 8 , PIT_CH0); /* MSB */
+ outb_p(delta & 0xff , PIT_CH0); /* LSB */
+ outb(delta >> 8 , PIT_CH0); /* MSB */
spin_unlock_irqrestore(&i8253_lock, flags);
}

/*
+ * On UP the PIT can serve all of the possible timer functions. On SMP systems
+ * it can be solely used for the global tick.
+ *
+ * The profiling and update capabilites are switched off once the local apic is
+ * registered. This mechanism replaces the previous #ifdef LOCAL_APIC -
+ * !using_apic_timer decisions in do_timer_interrupt_hook()
+ */
+struct clock_event_device pit_clockevent = {
+ .name = "pit",
+ .capabilities = CLOCK_CAP_TICK | CLOCK_CAP_PROFILE | CLOCK_CAP_UPDATE
+#ifndef CONFIG_SMP
+ | CLOCK_CAP_NEXTEVT
+#endif
+ ,
+ .set_mode = init_pit_timer,
+ .set_next_event = pit_next_event,
+ .shift = 32,
+};
+
+/*
+ * Initialize the conversion factor and the min/max deltas of the clock event
+ * structure and register the clock event source with the framework.
+ */
+void __init setup_pit_timer(void)
+{
+ pit_clockevent.mult = div_sc(CLOCK_TICK_RATE, NSEC_PER_SEC, 32);
+ pit_clockevent.max_delta_ns =
+ clockevent_delta2ns(0x7FFF, &pit_clockevent);
+ pit_clockevent.min_delta_ns =
+ clockevent_delta2ns(0xF, &pit_clockevent);
+ register_global_clockevent(&pit_clockevent);
+#ifdef CONFIG_HPET_TIMER
+ global_clock_event = &pit_clockevent;
+#endif
+}
+
+/*
* Since the PIT overflows every tick, its not very useful
* to just read by itself. So use jiffies to emulate a free
* running counter:
@@ -46,7 +124,7 @@ static cycle_t pit_read(void)
static u32 old_jifs;

spin_lock_irqsave(&i8253_lock, flags);
- /*
+ /*
* Although our caller may have the read side of xtime_lock,
* this is now a seqlock, and we are cheating in this routine
* by having side effects on state that we cannot undo if
Index: linux-2.6.18-mm2/arch/i386/kernel/time.c
===================================================================
--- linux-2.6.18-mm2.orig/arch/i386/kernel/time.c 2006-10-02 00:55:50.000000000 +0200
+++ linux-2.6.18-mm2/arch/i386/kernel/time.c 2006-10-02 00:55:53.000000000 +0200
@@ -163,15 +163,6 @@ EXPORT_SYMBOL(profile_pc);
*/
irqreturn_t timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
- /*
- * Here we are in the timer irq handler. We just have irqs locally
- * disabled but we don't know if the timer_bh is running on the other
- * CPU. We need to avoid to SMP race with it. NOTE: we don' t need
- * the irq version of write_lock because as just said we have irq
- * locally disabled. -arca
- */
- write_seqlock(&xtime_lock);
-
#ifdef CONFIG_X86_IO_APIC
if (timer_ack) {
/*
@@ -190,7 +181,6 @@ irqreturn_t timer_interrupt(int irq, voi

do_timer_interrupt_hook(regs);

-
if (MCA_bus) {
/* The PS/2 uses level-triggered interrupts. You can't
turn them off, nor would you want to (any attempt to
@@ -205,8 +195,6 @@ irqreturn_t timer_interrupt(int irq, voi
outb_p( irq|0x80, 0x61 ); /* reset the IRQ */
}

- write_sequnlock(&xtime_lock);
-
#ifdef CONFIG_X86_LOCAL_APIC
if (using_apic_timer)
smp_send_timer_broadcast_ipi(regs);
@@ -283,39 +271,6 @@ void notify_arch_cmos_timer(void)
mod_timer(&sync_cmos_timer, jiffies + 1);
}

-static int timer_resume(struct sys_device *dev)
-{
-#ifdef CONFIG_HPET_TIMER
- if (is_hpet_enabled())
- hpet_reenable();
-#endif
- setup_pit_timer();
-
- return 0;
-}
-
-static struct sysdev_class timer_sysclass = {
- .resume = timer_resume,
- set_kset_name("timer"),
-};
-
-
-/* XXX this driverfs stuff should probably go elsewhere later -john */
-static struct sys_device device_timer = {
- .id = 0,
- .cls = &timer_sysclass,
-};
-
-static int time_init_device(void)
-{
- int error = sysdev_class_register(&timer_sysclass);
- if (!error)
- error = sysdev_register(&device_timer);
- return error;
-}
-
-device_initcall(time_init_device);
-
#ifdef CONFIG_HPET_TIMER
extern void (*late_time_init)(void);
/* Duplicate of time_init() below, with hpet_enable part added */
Index: linux-2.6.18-mm2/include/asm-i386/i8253.h
===================================================================
--- linux-2.6.18-mm2.orig/include/asm-i386/i8253.h 2006-10-02 00:55:46.000000000 +0200
+++ linux-2.6.18-mm2/include/asm-i386/i8253.h 2006-10-02 00:55:53.000000000 +0200
@@ -3,4 +3,22 @@

extern spinlock_t i8253_lock;

+#ifdef CONFIG_HPET_TIMER
+extern struct clock_event_device *global_clock_event;
+#else
+extern struct clock_event_device pit_clockevent;
+# define global_clock_event (&pit_clockevent)
+#endif
+
+/**
+ * pit_interrupt_hook - hook into timer tick
+ * @regs: standard registers from interrupt
+ *
+ * Call the global clock event handler.
+ **/
+static inline void pit_interrupt_hook(struct pt_regs *regs)
+{
+ global_clock_event->event_handler(regs);
+}
+
#endif /* __ASM_I8253_H__ */
Index: linux-2.6.18-mm2/include/asm-i386/mach-default/do_timer.h
===================================================================
--- linux-2.6.18-mm2.orig/include/asm-i386/mach-default/do_timer.h 2006-10-02 00:55:46.000000000 +0200
+++ linux-2.6.18-mm2/include/asm-i386/mach-default/do_timer.h 2006-10-02 00:55:53.000000000 +0200
@@ -1,39 +1,20 @@
/* defines for inline arch setup functions */
+#include <linux/clockchips.h>

-#include <asm/apic.h>
#include <asm/i8259.h>
+#include <asm/i8253.h>

/**
* do_timer_interrupt_hook - hook into timer tick
* @regs: standard registers from interrupt
*
- * Description:
- * This hook is called immediately after the timer interrupt is ack'd.
- * It's primary purpose is to allow architectures that don't possess
- * individual per CPU clocks (like the CPU APICs supply) to broadcast the
- * timer interrupt as a means of triggering reschedules etc.
+ * Call the pit clock event handler. see asm/i8253.h
**/
-
static inline void do_timer_interrupt_hook(struct pt_regs *regs)
{
- do_timer(1);
-#ifndef CONFIG_SMP
- update_process_times(user_mode_vm(regs));
-#endif
-/*
- * In the SMP case we use the local APIC timer interrupt to do the
- * profiling, except when we simulate SMP mode on a uniprocessor
- * system, in that case we have to call the local interrupt handler.
- */
-#ifndef CONFIG_X86_LOCAL_APIC
- profile_tick(CPU_PROFILING, regs);
-#else
- if (!using_apic_timer)
- smp_local_timer_interrupt(regs);
-#endif
+ pit_interrupt_hook(regs);
}

-
/* you can safely undefine this if you don't have the Neptune chipset */

#define BUGGY_NEPTUN_TIMER
Index: linux-2.6.18-mm2/include/asm-i386/mach-visws/do_timer.h
===================================================================
--- linux-2.6.18-mm2.orig/include/asm-i386/mach-visws/do_timer.h 2006-10-02 00:55:46.000000000 +0200
+++ linux-2.6.18-mm2/include/asm-i386/mach-visws/do_timer.h 2006-10-02 00:55:53.000000000 +0200
@@ -9,7 +9,9 @@ static inline void do_timer_interrupt_ho
/* Clear the interrupt */
co_cpu_write(CO_CPU_STAT,co_cpu_read(CO_CPU_STAT) & ~CO_STAT_TIMEINTR);

+ write_seqlock(&xtime_lock);
do_timer(1);
+ write_sequnlock(&xtime_lock);
#ifndef CONFIG_SMP
update_process_times(user_mode_vm(regs));
#endif
Index: linux-2.6.18-mm2/include/asm-i386/mach-voyager/do_timer.h
===================================================================
--- linux-2.6.18-mm2.orig/include/asm-i386/mach-voyager/do_timer.h 2006-10-02 00:55:46.000000000 +0200
+++ linux-2.6.18-mm2/include/asm-i386/mach-voyager/do_timer.h 2006-10-02 00:55:53.000000000 +0200
@@ -1,13 +1,18 @@
/* defines for inline arch setup functions */
+#include <linux/clockchips.h>
+
#include <asm/voyager.h>
+#include <asm/i8253.h>

+/**
+ * do_timer_interrupt_hook - hook into timer tick
+ * @regs: standard registers from interrupt
+ *
+ * Call the pit clock event handler. see asm/i8253.h
+ **/
static inline void do_timer_interrupt_hook(struct pt_regs *regs)
{
- do_timer(1);
-#ifndef CONFIG_SMP
- update_process_times(user_mode_vm(regs));
-#endif
-
+ pit_interrupt_hook(regs);
voyager_timer_interrupt(regs);
}

--

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