timekeeping: Increase granularity of read_persistent_clock()

The persistent clock of some architectures (e.g. s390) have a
better granularity than seconds. To reduce the delta between the
host clock and the guest clock in a virtualized system change the
read_persistent_clock function to return a struct timespec.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Daniel Walker <dwalker@fifo99.com>
LKML-Reference: <20090814134811.013873340@de.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/arch/m68knommu/kernel/time.c b/arch/m68knommu/kernel/time.c
index d182b2f..6843224 100644 (file)
--- a/arch/m68knommu/kernel/time.c
+++ b/arch/m68knommu/kernel/time.c
@@ -72,9 +72,10 @@ static unsigned long read_rtc_mmss(void)
        return  mktime(year, mon, day, hour, min, sec);;
 }
 
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
 {
-       return read_rtc_mmss();
+       ts->tv_sec = read_rtc_mmss();
+       ts->tv_nsec = 0;
 }
 
 int update_persistent_clock(struct timespec now)

diff --git a/arch/mips/dec/time.c b/arch/mips/dec/time.c
index 463136e..02f505f 100644 (file)
--- a/arch/mips/dec/time.c
+++ b/arch/mips/dec/time.c
@@ -18,7 +18,7 @@
 #include <asm/dec/ioasic.h>
 #include <asm/dec/machtype.h>
 
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
 {
        unsigned int year, mon, day, hour, min, sec, real_year;
        unsigned long flags;
@@ -53,7 +53,8 @@ unsigned long read_persistent_clock(void)
 
        year += real_year - 72 + 2000;
 
-       return mktime(year, mon, day, hour, min, sec);
+       ts->tv_sec = mktime(year, mon, day, hour, min, sec);
+       ts->tv_nsec = 0;
 }
 
 /*

diff --git a/arch/mips/lasat/ds1603.c b/arch/mips/lasat/ds1603.c
index 52cb143..c6fd96f 100644 (file)
--- a/arch/mips/lasat/ds1603.c
+++ b/arch/mips/lasat/ds1603.c
@@ -135,7 +135,7 @@ static void rtc_end_op(void)
        lasat_ndelay(1000);
 }
 
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
 {
        unsigned long word;
        unsigned long flags;
@@ -147,7 +147,8 @@ unsigned long read_persistent_clock(void)
        rtc_end_op();
        spin_unlock_irqrestore(&rtc_lock, flags);
 
-       return word;
+       ts->tv_sec = word;
+       ts->tv_nsec = 0;
 }
 
 int rtc_mips_set_mmss(unsigned long time)

diff --git a/arch/mips/lasat/sysctl.c b/arch/mips/lasat/sysctl.c
index 8f88886..3f04d4c 100644 (file)
--- a/arch/mips/lasat/sysctl.c
+++ b/arch/mips/lasat/sysctl.c
@@ -92,10 +92,12 @@ static int rtctmp;
 int proc_dolasatrtc(ctl_table *table, int write, struct file *filp,
                       void *buffer, size_t *lenp, loff_t *ppos)
 {
+       struct timespec ts;
        int r;
 
        if (!write) {
-               rtctmp = read_persistent_clock();
+               read_persistent_clock(&ts);
+               rtctmp = ts.tv_sec;
                /* check for time < 0 and set to 0 */
                if (rtctmp < 0)
                        rtctmp = 0;
@@ -134,9 +136,11 @@ int sysctl_lasat_rtc(ctl_table *table,
                    void *oldval, size_t *oldlenp,
                    void *newval, size_t newlen)
 {
+       struct timespec ts;
        int r;
 
-       rtctmp = read_persistent_clock();
+       read_persistent_clock(&ts);
+       rtctmp = ts.tv_sec;
        if (rtctmp < 0)
                rtctmp = 0;
        r = sysctl_intvec(table, oldval, oldlenp, newval, newlen);

diff --git a/arch/mips/lemote/lm2e/setup.c b/arch/mips/lemote/lm2e/setup.c
index ebd6cea..24b355d 100644 (file)
--- a/arch/mips/lemote/lm2e/setup.c
+++ b/arch/mips/lemote/lm2e/setup.c
@@ -54,9 +54,10 @@ void __init plat_time_init(void)
        mips_hpt_frequency = cpu_clock_freq / 2;
 }
 
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
 {
-       return mc146818_get_cmos_time();
+       ts->tv_sec = mc146818_get_cmos_time();
+       ts->tv_nsec = 0;
 }
 
 void (*__wbflush)(void);

diff --git a/arch/mips/mti-malta/malta-time.c b/arch/mips/mti-malta/malta-time.c
index 0b97d47..3c6f190 100644 (file)
--- a/arch/mips/mti-malta/malta-time.c
+++ b/arch/mips/mti-malta/malta-time.c
@@ -100,9 +100,10 @@ static unsigned int __init estimate_cpu_frequency(void)
        return count;
 }
 
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
 {
-       return mc146818_get_cmos_time();
+       ts->tv_sec = mc146818_get_cmos_time();
+       ts->tv_nsec = 0;
 }
 
 static void __init plat_perf_setup(void)

diff --git a/arch/mips/pmc-sierra/yosemite/setup.c b/arch/mips/pmc-sierra/yosemite/setup.c
index 2d3c0dc..3498ac9 100644 (file)
--- a/arch/mips/pmc-sierra/yosemite/setup.c
+++ b/arch/mips/pmc-sierra/yosemite/setup.c
@@ -70,7 +70,7 @@ void __init bus_error_init(void)
 }
 
 
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
 {
        unsigned int year, month, day, hour, min, sec;
        unsigned long flags;
@@ -92,7 +92,8 @@ unsigned long read_persistent_clock(void)
        m48t37_base->control = 0x00;
        spin_unlock_irqrestore(&rtc_lock, flags);
 
-       return mktime(year, month, day, hour, min, sec);
+       ts->tv_sec = mktime(year, month, day, hour, min, sec);
+       ts->tv_nsec = 0;
 }
 
 int rtc_mips_set_time(unsigned long tim)

diff --git a/arch/mips/sibyte/swarm/setup.c b/arch/mips/sibyte/swarm/setup.c
index 672e45d..623ffc9 100644 (file)
--- a/arch/mips/sibyte/swarm/setup.c
+++ b/arch/mips/sibyte/swarm/setup.c
@@ -87,19 +87,26 @@ enum swarm_rtc_type {
 
 enum swarm_rtc_type swarm_rtc_type;
 
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
 {
+       unsigned long sec;
+
        switch (swarm_rtc_type) {
        case RTC_XICOR:
-               return xicor_get_time();
+               sec = xicor_get_time();
+               break;
 
        case RTC_M4LT81:
-               return m41t81_get_time();
+               sec = m41t81_get_time();
+               break;
 
        case RTC_NONE:
        default:
-               return mktime(2000, 1, 1, 0, 0, 0);
+               sec = mktime(2000, 1, 1, 0, 0, 0);
+               break;
        }
+       ts->tv_sec = sec;
+       tv->tv_nsec = 0;
 }
 
 int rtc_mips_set_time(unsigned long sec)

diff --git a/arch/mips/sni/time.c b/arch/mips/sni/time.c
index 0d9ec1a..62df6a5 100644 (file)
--- a/arch/mips/sni/time.c
+++ b/arch/mips/sni/time.c
@@ -182,7 +182,8 @@ void __init plat_time_init(void)
        setup_pit_timer();
 }
 
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
 {
-       return -1;
+       ts->tv_sec = -1;
+       ts->tv_nsec = 0;
 }

diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index eae4511..ad63f30 100644 (file)
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -769,7 +769,7 @@ int update_persistent_clock(struct timespec now)
        return ppc_md.set_rtc_time(&tm);
 }
 
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
 {
        struct rtc_time tm;
        static int first = 1;
@@ -787,8 +787,9 @@ unsigned long read_persistent_clock(void)
        if (!ppc_md.get_rtc_time)
                return 0;
        ppc_md.get_rtc_time(&tm);
-       return mktime(tm.tm_year+1900, tm.tm_mon+1, tm.tm_mday,
-                     tm.tm_hour, tm.tm_min, tm.tm_sec);
+       ts->tv_sec = mktime(tm.tm_year+1900, tm.tm_mon+1, tm.tm_mday,
+                           tm.tm_hour, tm.tm_min, tm.tm_sec);
+       ts->tv_nsec = 0;
 }
 
 /* clocksource code */

diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index e76c2e7..a94ec48 100644 (file)
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -182,12 +182,9 @@ static void timing_alert_interrupt(__u16 code)
 static void etr_reset(void);
 static void stp_reset(void);
 
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
 {
-       struct timespec ts;
-
-       tod_to_timeval(get_clock() - TOD_UNIX_EPOCH, &ts);
-       return ts.tv_sec;
+       tod_to_timeval(get_clock() - TOD_UNIX_EPOCH, ts);
 }
 
 static cycle_t read_tod_clock(struct clocksource *cs)
@@ -248,7 +245,6 @@ void __init time_init(void)
 {
        struct timespec ts;
        unsigned long flags;
-       cycle_t now;
 
        /* Reset time synchronization interfaces. */
        etr_reset();
@@ -266,20 +262,10 @@ void __init time_init(void)
                panic("Could not register TOD clock source");
 
        /*
-        * The TOD clock is an accurate clock. The xtime should be
-        * initialized in a way that the difference between TOD and
-        * xtime is reasonably small. Too bad that timekeeping_init
-        * sets xtime.tv_nsec to zero. In addition the clock source
-        * change from the jiffies clock source to the TOD clock
-        * source add another error of up to 1/HZ second. The same
-        * function sets wall_to_monotonic to a value that is too
-        * small for /proc/uptime to be accurate.
-        * Reset xtime and wall_to_monotonic to sane values.
+        * Reset wall_to_monotonic to the initial timestamp created
+        * in head.S to get a precise value in /proc/uptime.
         */
        write_seqlock_irqsave(&xtime_lock, flags);
-       now = get_clock();
-       tod_to_timeval(now - TOD_UNIX_EPOCH, &xtime);
-       clocksource_tod.cycle_last = now;
        tod_to_timeval(sched_clock_base_cc - TOD_UNIX_EPOCH, &ts);
        set_normalized_timespec(&wall_to_monotonic, -ts.tv_sec, -ts.tv_nsec);
        write_sequnlock_irqrestore(&xtime_lock, flags);

diff --git a/arch/sh/kernel/time.c b/arch/sh/kernel/time.c
index 9b352a1..3f4706a 100644 (file)
--- a/arch/sh/kernel/time.c
+++ b/arch/sh/kernel/time.c
@@ -39,11 +39,9 @@ void (*rtc_sh_get_time)(struct timespec *) = null_rtc_get_time;
 int (*rtc_sh_set_time)(const time_t) = null_rtc_set_time;
 
 #ifdef CONFIG_GENERIC_CMOS_UPDATE
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
 {
-       struct timespec tv;
-       rtc_sh_get_time(&tv);
-       return tv.tv_sec;
+       rtc_sh_get_time(&ts);
 }
 
 int update_persistent_clock(struct timespec now)

diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c
index 5d465b2..bf67dcb 100644 (file)
--- a/arch/x86/kernel/rtc.c
+++ b/arch/x86/kernel/rtc.c
@@ -178,7 +178,7 @@ static int set_rtc_mmss(unsigned long nowtime)
 }
 
 /* not static: needed by APM */
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
 {
        unsigned long retval, flags;
 
@@ -186,7 +186,8 @@ unsigned long read_persistent_clock(void)
        retval = get_wallclock();
        spin_unlock_irqrestore(&rtc_lock, flags);
 
-       return retval;
+       ts->tv_sec = retval;
+       ts->tv_nsec = 0;
 }
 
 int update_persistent_clock(struct timespec now)

diff --git a/arch/xtensa/kernel/time.c b/arch/xtensa/kernel/time.c
index 8848120..19085ff 100644 (file)
--- a/arch/xtensa/kernel/time.c
+++ b/arch/xtensa/kernel/time.c
@@ -59,9 +59,8 @@ static struct irqaction timer_irqaction = {
 
 void __init time_init(void)
 {
-       xtime.tv_nsec = 0;
-       xtime.tv_sec = read_persistent_clock();
-
+       /* FIXME: xtime&wall_to_monotonic are set in timekeeping_init. */
+       read_persistent_clock(&xtime);
        set_normalized_timespec(&wall_to_monotonic,
                -xtime.tv_sec, -xtime.tv_nsec);
 

diff --git a/include/linux/time.h b/include/linux/time.h
index e7c8445..53a3216 100644 (file)
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -101,7 +101,7 @@ extern struct timespec xtime;
 extern struct timespec wall_to_monotonic;
 extern seqlock_t xtime_lock;
 
-extern unsigned long read_persistent_clock(void);
+extern void read_persistent_clock(struct timespec *ts);
 extern int update_persistent_clock(struct timespec now);
 extern int no_sync_cmos_clock __read_mostly;
 void timekeeping_init(void);

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 41579e7..f1a21ce 100644 (file)
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -154,7 +154,7 @@ __cacheline_aligned_in_smp DEFINE_SEQLOCK(xtime_lock);
  */
 struct timespec xtime __attribute__ ((aligned (16)));
 struct timespec wall_to_monotonic __attribute__ ((aligned (16)));
-static unsigned long total_sleep_time;         /* seconds */
+static struct timespec total_sleep_time;
 
 /*
  * The raw monotonic time for the CLOCK_MONOTONIC_RAW posix clock.
@@ -487,17 +487,18 @@ int timekeeping_valid_for_hres(void)
 }
 
 /**
- * read_persistent_clock -  Return time in seconds from the persistent clock.
+ * read_persistent_clock -  Return time from the persistent clock.
  *
  * Weak dummy function for arches that do not yet support it.
- * Returns seconds from epoch using the battery backed persistent clock.
- * Returns zero if unsupported.
+ * Reads the time from the battery backed persistent clock.
+ * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
  *
  *  XXX - Do be sure to remove it once all arches implement it.
  */
-unsigned long __attribute__((weak)) read_persistent_clock(void)
+void __attribute__((weak)) read_persistent_clock(struct timespec *ts)
 {
-       return 0;
+       ts->tv_sec = 0;
+       ts->tv_nsec = 0;
 }
 
 /*
@@ -507,7 +508,9 @@ void __init timekeeping_init(void)
 {
        struct clocksource *clock;
        unsigned long flags;
-       unsigned long sec = read_persistent_clock();
+       struct timespec now;
+
+       read_persistent_clock(&now);
 
        write_seqlock_irqsave(&xtime_lock, flags);
 
@@ -518,19 +521,20 @@ void __init timekeeping_init(void)
                clock->enable(clock);
        timekeeper_setup_internals(clock);
 
-       xtime.tv_sec = sec;
-       xtime.tv_nsec = 0;
+       xtime.tv_sec = now.tv_sec;
+       xtime.tv_nsec = now.tv_nsec;
        raw_time.tv_sec = 0;
        raw_time.tv_nsec = 0;
        set_normalized_timespec(&wall_to_monotonic,
                -xtime.tv_sec, -xtime.tv_nsec);
        update_xtime_cache(0);
-       total_sleep_time = 0;
+       total_sleep_time.tv_sec = 0;
+       total_sleep_time.tv_nsec = 0;
        write_sequnlock_irqrestore(&xtime_lock, flags);
 }
 
 /* time in seconds when suspend began */
-static unsigned long timekeeping_suspend_time;
+static struct timespec timekeeping_suspend_time;
 
 /**
  * timekeeping_resume - Resumes the generic timekeeping subsystem.
@@ -543,18 +547,19 @@ static unsigned long timekeeping_suspend_time;
 static int timekeeping_resume(struct sys_device *dev)
 {
        unsigned long flags;
-       unsigned long now = read_persistent_clock();
+       struct timespec ts;
+
+       read_persistent_clock(&ts);
 
        clocksource_resume();
 
        write_seqlock_irqsave(&xtime_lock, flags);
 
-       if (now && (now > timekeeping_suspend_time)) {
-               unsigned long sleep_length = now - timekeeping_suspend_time;
-
-               xtime.tv_sec += sleep_length;
-               wall_to_monotonic.tv_sec -= sleep_length;
-               total_sleep_time += sleep_length;
+       if (timespec_compare(&ts, &timekeeping_suspend_time) > 0) {
+               ts = timespec_sub(ts, timekeeping_suspend_time);
+               xtime = timespec_add_safe(xtime, ts);
+               wall_to_monotonic = timespec_sub(wall_to_monotonic, ts);
+               total_sleep_time = timespec_add_safe(total_sleep_time, ts);
        }
        update_xtime_cache(0);
        /* re-base the last cycle value */
@@ -577,7 +582,7 @@ static int timekeeping_suspend(struct sys_device *dev, pm_message_t state)
 {
        unsigned long flags;
 
-       timekeeping_suspend_time = read_persistent_clock();
+       read_persistent_clock(&timekeeping_suspend_time);
 
        write_seqlock_irqsave(&xtime_lock, flags);
        timekeeping_forward_now();
@@ -801,9 +806,10 @@ void update_wall_time(void)
  */
 void getboottime(struct timespec *ts)
 {
-       set_normalized_timespec(ts,
-               - (wall_to_monotonic.tv_sec + total_sleep_time),
-               - wall_to_monotonic.tv_nsec);
+       struct timespec boottime;
+
+       boottime = timespec_add_safe(wall_to_monotonic, total_sleep_time);
+       set_normalized_timespec(ts, -boottime.tv_sec, -boottime.tv_nsec);
 }
 
 /**
@@ -812,7 +818,7 @@ void getboottime(struct timespec *ts)
  */
 void monotonic_to_bootbased(struct timespec *ts)
 {
-       ts->tv_sec += total_sleep_time;
+       *ts = timespec_add_safe(*ts, total_sleep_time);
 }
 
 unsigned long get_seconds(void)