xen/arch/x86/time.c


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/******************************************************************************
 * arch/x86/time.c
 * 
 * Per-CPU time calibration and management.
 * 
 * Copyright (c) 2002-2005, K A Fraser
 * 
 * Portions from Linux are:
 * Copyright (c) 1991, 1992, 1995  Linus Torvalds
 */

#include <xen/config.h>
#include <xen/errno.h>
#include <xen/event.h>
#include <xen/sched.h>
#include <xen/lib.h>
#include <xen/config.h>
#include <xen/init.h>
#include <xen/time.h>
#include <xen/timer.h>
#include <xen/smp.h>
#include <xen/irq.h>
#include <xen/softirq.h>
#include <asm/io.h>
#include <asm/msr.h>
#include <asm/mpspec.h>
#include <asm/processor.h>
#include <asm/fixmap.h>
#include <asm/mc146818rtc.h>
#include <asm/div64.h>
#include <asm/hpet.h>
#include <io_ports.h>

/* opt_clocksource: Force clocksource to one of: pit, hpet, cyclone, acpi. */
static char opt_clocksource[10];
string_param("clocksource", opt_clocksource);

/*
 * opt_consistent_tscs: All TSCs tick at the exact same rate, allowing
 * simplified system time handling.
 */
static int opt_consistent_tscs;
boolean_param("consistent_tscs", opt_consistent_tscs);

unsigned long cpu_khz;  /* CPU clock frequency in kHz. */
DEFINE_SPINLOCK(rtc_lock);
unsigned long pit0_ticks;
static u32 wc_sec, wc_nsec; /* UTC time at last 'time update'. */
static DEFINE_SPINLOCK(wc_lock);

struct time_scale {
    int shift;
    u32 mul_frac;
};

struct cpu_time {
    u64 local_tsc_stamp;
    s_time_t stime_local_stamp;
    s_time_t stime_master_stamp;
    struct time_scale tsc_scale;
};

struct platform_timesource {
    char *id;
    char *name;
    u64 frequency;
    u64 (*read_counter)(void);
    int (*init)(struct platform_timesource *);
    void (*resume)(struct platform_timesource *);
    int counter_bits;
};

static DEFINE_PER_CPU(struct cpu_time, cpu_time);

/* Calibrate all CPUs to platform timer every EPOCH. */
#define EPOCH MILLISECS(1000)
static struct timer calibration_timer;

/*
 * We simulate a 32-bit platform timer from the 16-bit PIT ch2 counter.
 * Otherwise overflow happens too quickly (~50ms) for us to guarantee that
 * softirq handling will happen in time.
 * 
 * The pit_lock protects the 16- and 32-bit stamp fields as well as the 
 */
static DEFINE_SPINLOCK(pit_lock);
static u16 pit_stamp16;
static u32 pit_stamp32;
static int using_pit;

/*
 * 32-bit division of integer dividend and integer divisor yielding
 * 32-bit fractional quotient.
 */
static inline u32 div_frac(u32 dividend, u32 divisor)
{
    u32 quotient, remainder;
    ASSERT(dividend < divisor);
    asm ( 
        "divl %4"
        : "=a" (quotient), "=d" (remainder)
        : "0" (0), "1" (dividend), "r" (divisor) );
    return quotient;
}

/*
 * 32-bit multiplication of multiplicand and fractional multiplier
 * yielding 32-bit product (radix point at same position as in multiplicand).
 */
static inline u32 mul_frac(u32 multiplicand, u32 multiplier)
{
    u32 product_int, product_frac;
    asm (
        "mul %3"
        : "=a" (product_frac), "=d" (product_int)
        : "0" (multiplicand), "r" (multiplier) );
    return product_int;
}

/*
 * Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction,
 * yielding a 64-bit result.
 */
static inline u64 scale_delta(u64 delta, struct time_scale *scale)
{
    u64 product;
#ifdef CONFIG_X86_32
    u32 tmp1, tmp2;
#endif

    if ( scale->shift < 0 )
        delta >>= -scale->shift;
    else
        delta <<= scale->shift;

#ifdef CONFIG_X86_32
    asm (
        "mul  %5       ; "
        "mov  %4,%%eax ; "
        "mov  %%edx,%4 ; "
        "mul  %5       ; "
        "xor  %5,%5    ; "
        "add  %4,%%eax ; "
        "adc  %5,%%edx ; "
        : "=A" (product), "=r" (tmp1), "=r" (tmp2)
        : "a" ((u32)delta), "1" ((u32)(delta >> 32)), "2" (scale->mul_frac) );
#else
    asm (
        "mul %%rdx ; shrd $32,%%rdx,%%rax"
        : "=a" (product) : "0" (delta), "d" ((u64)scale->mul_frac) );
#endif

    return product;
}

/* Compute the reciprocal of the given time_scale. */
static inline struct time_scale scale_reciprocal(struct time_scale scale)
{
    struct time_scale reciprocal;
    u32 dividend;

    dividend = 0x80000000u;
    reciprocal.shift = 1 - scale.shift;
    while ( unlikely(dividend >= scale.mul_frac) )
    {
        dividend >>= 1;
        reciprocal.shift++;
    }

    asm (
        "divl %4"
        : "=a" (reciprocal.mul_frac), "=d" (dividend)
        : "0" (0), "1" (dividend), "r" (scale.mul_frac) );

    return reciprocal;
}

/*
 * cpu_mask that denotes the CPUs that needs timer interrupt coming in as
 * IPIs in place of local APIC timers
 */
extern int xen_cpuidle;
static cpumask_t pit_broadcast_mask;

static void smp_send_timer_broadcast_ipi(void)
{
    int cpu = smp_processor_id();
    cpumask_t mask;

    cpus_and(mask, cpu_online_map, pit_broadcast_mask);

    if ( cpu_isset(cpu, mask) )
    {
        cpu_clear(cpu, mask);
        raise_softirq(TIMER_SOFTIRQ);
    }