Patchwork [v6,2/7] RTC: Update the RTC clock only when reading it

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Submitter Zhang, Yang Z
Date May 17, 2012, 2:28 a.m.
Message ID <A9667DDFB95DB7438FA9D7D576C3D87E13A7EC@SHSMSX101.ccr.corp.intel.com>
Download mbox | patch
Permalink /patch/159798/
State New
Headers show

Comments

Zhang, Yang Z - May 17, 2012, 2:28 a.m.
Use offset instead of timer to calculate guest rtc. Guest rtc is calculated by (base_rtc + guest_time_now - guest_time_last_update_rtc + offset).
Base_rtc means the rtc value of last update. 
Guest_time_now means the guest time that access happens.
Guest_time_last_update means the guest time of last update rtc.
Offset is used when divider reset happened or set bit is changed.

Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com>
---
 hw/mc146818rtc.c |  209 ++++++++++++++++++------------------------------------
 qemu-timer.h     |    5 ++
 2 files changed, 73 insertions(+), 141 deletions(-)

--
1.7.1
Paolo Bonzini - May 17, 2012, 10:38 a.m.
Note: I haven't tested this series yet.  Thanks for finding the problem!

Il 17/05/2012 04:28, Zhang, Yang Z ha scritto:
> Use offset instead of timer to calculate guest rtc. Guest rtc is calculated by (base_rtc + guest_time_now - guest_time_last_update_rtc + offset).
> Base_rtc means the rtc value of last update. 
> Guest_time_now means the guest time that access happens.
> Guest_time_last_update means the guest time of last update rtc.
> Offset is used when divider reset happened or set bit is changed.
> 
> +static void rtc_set_offset(RTCState *s, bool running, bool div_reset)
> +{
> +    if (div_reset)
> +        s->offset = 500000;
> +    else if (!running)
> +        s->offset = s->old_guest_usec % USEC_PER_SEC;
> +}

This is probably clearer if you just inline it at the appropriate
places---especially because rtc_set_offset(s, 0, 0) is a no-op.

> -static void rtc_update_second(void *opaque)
> -{
> -    RTCState *s = opaque;
> -    int64_t delay;
> -
> -    /* if the oscillator is not in normal operation, we do not update */
> -    if ((s->cmos_data[RTC_REG_A] & 0x70) != 0x20) {
> -        s->next_second_time += get_ticks_per_sec();
> -        qemu_mod_timer(s->second_timer, s->next_second_time);
> -    } else {
> -        rtc_next_second(&s->current_tm);
> -
> -        if (!(s->cmos_data[RTC_REG_B] & REG_B_SET)) {
> -            /* update in progress bit */
> -            s->cmos_data[RTC_REG_A] |= REG_A_UIP;
> -        }
> -        /* should be 244 us = 8 / 32768 seconds, but currently the
> -           timers do not have the necessary resolution. */
> -        delay = (get_ticks_per_sec() * 1) / 100;
> -        if (delay < 1)
> -            delay = 1;
> -        qemu_mod_timer(s->second_timer2,
> -                       s->next_second_time + delay);
> -    }
> -}

This patch breaks REG_A_UIP.  You can squash patches 2 and 3 together to
avoid this problem.

Paolo

Patch

diff --git a/hw/mc146818rtc.c b/hw/mc146818rtc.c
index 1ccfb50..24db5cf 100644
--- a/hw/mc146818rtc.c
+++ b/hw/mc146818rtc.c
@@ -45,6 +45,9 @@ 
 # define DPRINTF_C(format, ...)      do { } while (0)
 #endif

+#define USEC_PER_SEC    1000000L
+#define NS_PER_USEC     1000L
+
 #define RTC_REINJECT_ON_ACK_COUNT 20

 typedef struct RTCState {
@@ -54,27 +57,38 @@  typedef struct RTCState {
     uint8_t cmos_index;
     struct tm current_tm;
     int32_t base_year;
+    uint64_t base_rtc;
+    uint64_t last_update;
+    int64_t offset;
+    uint64_t old_guest_usec;
     qemu_irq irq;
     qemu_irq sqw_irq;
     int it_shift;
     /* periodic timer */
     QEMUTimer *periodic_timer;
     int64_t next_periodic_time;
-    /* second update */
-    int64_t next_second_time;
     uint16_t irq_reinject_on_ack_count;
     uint32_t irq_coalesced;
     uint32_t period;
     QEMUTimer *coalesced_timer;
-    QEMUTimer *second_timer;
-    QEMUTimer *second_timer2;
     Notifier clock_reset_notifier;
     LostTickPolicy lost_tick_policy;
     Notifier suspend_notifier;
 } RTCState;

 static void rtc_set_time(RTCState *s);
-static void rtc_copy_date(RTCState *s);
+static void rtc_calibrate_time(RTCState *s);
+static void rtc_set_cmos(RTCState *s);
+
+static uint64_t get_guest_rtc_us(RTCState *s)
+{
+    uint64_t guest_rtc;
+    uint64_t guest_clock = qemu_get_clock_us(rtc_clock);
+
+    guest_rtc = s->base_rtc * USEC_PER_SEC
+                 + guest_clock - s->last_update + s->offset;
+    return guest_rtc;
+}

 #ifdef TARGET_I386
 static void rtc_coalesced_timer_update(RTCState *s)
@@ -175,6 +189,14 @@  static void rtc_periodic_timer(void *opaque)
     }
 }

+static void rtc_set_offset(RTCState *s, bool running, bool div_reset)
+{
+    if (div_reset)
+        s->offset = 500000;
+    else if (!running)
+        s->offset = s->old_guest_usec % USEC_PER_SEC;
+}
+
 static void cmos_ioport_write(void *opaque, uint32_t addr, uint32_t data)
 {
     RTCState *s = opaque;
@@ -201,6 +223,7 @@  static void cmos_ioport_write(void *opaque, uint32_t addr, uint32_t data)
             /* if in set mode, do not update the time */
             if (!(s->cmos_data[RTC_REG_B] & REG_B_SET)) {
                 rtc_set_time(s);
+                rtc_set_offset(s, 1, 0);
             }
             break;
         case RTC_REG_A:
@@ -211,6 +234,12 @@  static void cmos_ioport_write(void *opaque, uint32_t addr, uint32_t data)
             break;
         case RTC_REG_B:
             if (data & REG_B_SET) {
+                /* update cmos to when the rtc was stopping */
+                if (!(s->cmos_data[RTC_REG_B] & REG_B_SET)) {
+                    rtc_calibrate_time(s);
+                    rtc_set_cmos(s);
+                    s->old_guest_usec = get_guest_rtc_us(s);
+                }
                 /* set mode: reset UIP mode */
                 s->cmos_data[RTC_REG_A] &= ~REG_A_UIP;
                 data &= ~REG_B_UIE;
@@ -218,6 +247,7 @@  static void cmos_ioport_write(void *opaque, uint32_t addr, uint32_t data)
                 /* if disabling set mode, update the time */
                 if (s->cmos_data[RTC_REG_B] & REG_B_SET) {
                     rtc_set_time(s);
+                    rtc_set_offset(s, 0, 0);
                 }
             }
             s->cmos_data[RTC_REG_B] = data;
@@ -270,10 +300,13 @@  static void rtc_set_time(RTCState *s)
     tm->tm_mon = rtc_from_bcd(s, s->cmos_data[RTC_MONTH]) - 1;
     tm->tm_year = rtc_from_bcd(s, s->cmos_data[RTC_YEAR]) + s->base_year - 1900;

+    s->base_rtc = mktimegm(tm);
+    s->last_update = qemu_get_clock_us(rtc_clock);
+
     rtc_change_mon_event(tm);
 }

-static void rtc_copy_date(RTCState *s)
+static void rtc_set_cmos(RTCState *s)
 {
     const struct tm *tm = &s->current_tm;
     int year;
@@ -299,122 +332,16 @@  static void rtc_copy_date(RTCState *s)
     s->cmos_data[RTC_YEAR] = rtc_to_bcd(s, year);
 }

-/* month is between 0 and 11. */
-static int get_days_in_month(int month, int year)
-{
-    static const int days_tab[12] = {
-        31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
-    };
-    int d;
-    if ((unsigned )month >= 12)
-        return 31;
-    d = days_tab[month];
-    if (month == 1) {
-        if ((year % 4) == 0 && ((year % 100) != 0 || (year % 400) == 0))
-            d++;
-    }
-    return d;
-}
-
-/* update 'tm' to the next second */
-static void rtc_next_second(struct tm *tm)
+static void rtc_calibrate_time(RTCState *s)
 {
-    int days_in_month;
-
-    tm->tm_sec++;
-    if ((unsigned)tm->tm_sec >= 60) {
-        tm->tm_sec = 0;
-        tm->tm_min++;
-        if ((unsigned)tm->tm_min >= 60) {
-            tm->tm_min = 0;
-            tm->tm_hour++;
-            if ((unsigned)tm->tm_hour >= 24) {
-                tm->tm_hour = 0;
-                /* next day */
-                tm->tm_wday++;
-                if ((unsigned)tm->tm_wday >= 7)
-                    tm->tm_wday = 0;
-                days_in_month = get_days_in_month(tm->tm_mon,
-                                                  tm->tm_year + 1900);
-                tm->tm_mday++;
-                if (tm->tm_mday < 1) {
-                    tm->tm_mday = 1;
-                } else if (tm->tm_mday > days_in_month) {
-                    tm->tm_mday = 1;
-                    tm->tm_mon++;
-                    if (tm->tm_mon >= 12) {
-                        tm->tm_mon = 0;
-                        tm->tm_year++;
-                    }
-                }
-            }
-        }
-    }
-}
-
-
-static void rtc_update_second(void *opaque)
-{
-    RTCState *s = opaque;
-    int64_t delay;
-
-    /* if the oscillator is not in normal operation, we do not update */
-    if ((s->cmos_data[RTC_REG_A] & 0x70) != 0x20) {
-        s->next_second_time += get_ticks_per_sec();
-        qemu_mod_timer(s->second_timer, s->next_second_time);
-    } else {
-        rtc_next_second(&s->current_tm);
-
-        if (!(s->cmos_data[RTC_REG_B] & REG_B_SET)) {
-            /* update in progress bit */
-            s->cmos_data[RTC_REG_A] |= REG_A_UIP;
-        }
-        /* should be 244 us = 8 / 32768 seconds, but currently the
-           timers do not have the necessary resolution. */
-        delay = (get_ticks_per_sec() * 1) / 100;
-        if (delay < 1)
-            delay = 1;
-        qemu_mod_timer(s->second_timer2,
-                       s->next_second_time + delay);
-    }
-}
-
-static void rtc_update_second2(void *opaque)
-{
-    RTCState *s = opaque;
-
-    if (!(s->cmos_data[RTC_REG_B] & REG_B_SET)) {
-        rtc_copy_date(s);
-    }
-
-    /* check alarm */
-    if (((s->cmos_data[RTC_SECONDS_ALARM] & 0xc0) == 0xc0 ||
-         rtc_from_bcd(s, s->cmos_data[RTC_SECONDS_ALARM]) == s->current_tm.tm_sec) &&
-        ((s->cmos_data[RTC_MINUTES_ALARM] & 0xc0) == 0xc0 ||
-         rtc_from_bcd(s, s->cmos_data[RTC_MINUTES_ALARM]) == s->current_tm.tm_min) &&
-        ((s->cmos_data[RTC_HOURS_ALARM] & 0xc0) == 0xc0 ||
-         rtc_from_bcd(s, s->cmos_data[RTC_HOURS_ALARM]) == s->current_tm.tm_hour)) {
-
-        s->cmos_data[RTC_REG_C] |= REG_C_AF;
-        if (s->cmos_data[RTC_REG_B] & REG_B_AIE) {
-            qemu_system_wakeup_request(QEMU_WAKEUP_REASON_RTC);
-            qemu_irq_raise(s->irq);
-            s->cmos_data[RTC_REG_C] |= REG_C_IRQF;
-        }
-    }
-
-    /* update ended interrupt */
-    s->cmos_data[RTC_REG_C] |= REG_C_UF;
-    if (s->cmos_data[RTC_REG_B] & REG_B_UIE) {
-        s->cmos_data[RTC_REG_C] |= REG_C_IRQF;
-        qemu_irq_raise(s->irq);
-    }
-
-    /* clear update in progress bit */
-    s->cmos_data[RTC_REG_A] &= ~REG_A_UIP;
-
-    s->next_second_time += get_ticks_per_sec();
-    qemu_mod_timer(s->second_timer, s->next_second_time);
+    struct tm *ret;
+    time_t guest_sec;
+    int64_t guest_usec;
+
+    guest_usec = get_guest_rtc_us(s);
+    guest_sec = guest_usec / USEC_PER_SEC;
+    ret = gmtime(&guest_sec);
+    s->current_tm = *ret;
 }

 static uint32_t cmos_ioport_read(void *opaque, uint32_t addr)
@@ -432,6 +359,12 @@  static uint32_t cmos_ioport_read(void *opaque, uint32_t addr)
         case RTC_DAY_OF_MONTH:
         case RTC_MONTH:
         case RTC_YEAR:
+            /* if not in set mode, calibrate cmos before
+             * reading*/
+            if (!(s->cmos_data[RTC_REG_B] & REG_B_SET)) {
+                rtc_calibrate_time(s);
+                rtc_set_cmos(s);
+            }
             ret = s->cmos_data[s->cmos_index];
             break;
         case RTC_REG_A:
@@ -475,13 +408,6 @@  void rtc_set_memory(ISADevice *dev, int addr, int val)
         s->cmos_data[addr] = val;
 }

-void rtc_set_date(ISADevice *dev, const struct tm *tm)
-{
-    RTCState *s = DO_UPCAST(RTCState, dev, dev);
-    s->current_tm = *tm;
-    rtc_copy_date(s);
-}
-
 /* PC cmos mappings */
 #define REG_IBM_CENTURY_BYTE        0x32
 #define REG_IBM_PS2_CENTURY_BYTE    0x37
@@ -492,9 +418,15 @@  static void rtc_set_date_from_host(ISADevice *dev)
     struct tm tm;
     int val;

-    /* set the CMOS date */
     qemu_get_timedate(&tm, 0);
-    rtc_set_date(dev, &tm);
+
+    s->base_rtc = mktimegm(&tm);
+    s->last_update = qemu_get_clock_us(rtc_clock);
+    s->offset = 0;
+
+    /* set the CMOS date */
+    s->current_tm = tm;
+    rtc_set_cmos(s);

     val = rtc_to_bcd(s, (tm.tm_year / 100) + 19);
     rtc_set_memory(dev, REG_IBM_CENTURY_BYTE, val);
@@ -531,11 +463,12 @@  static const VMStateDescription vmstate_rtc = {
         VMSTATE_INT32(current_tm.tm_mday, RTCState),
         VMSTATE_INT32(current_tm.tm_mon, RTCState),
         VMSTATE_INT32(current_tm.tm_year, RTCState),
+        VMSTATE_UINT64(base_rtc, RTCState),
+        VMSTATE_UINT64(last_update, RTCState),
+        VMSTATE_INT64(offset, RTCState),
+        VMSTATE_UINT64(old_guest_usec, RTCState),
         VMSTATE_TIMER(periodic_timer, RTCState),
         VMSTATE_INT64(next_periodic_time, RTCState),
-        VMSTATE_INT64(next_second_time, RTCState),
-        VMSTATE_TIMER(second_timer, RTCState),
-        VMSTATE_TIMER(second_timer2, RTCState),
         VMSTATE_UINT32_V(irq_coalesced, RTCState, 2),
         VMSTATE_UINT32_V(period, RTCState, 2),
         VMSTATE_END_OF_LIST()
@@ -548,8 +481,6 @@  static void rtc_notify_clock_reset(Notifier *notifier, void *data)
     int64_t now = *(int64_t *)data;

     rtc_set_date_from_host(&s->dev);
-    s->next_second_time = now + (get_ticks_per_sec() * 99) / 100;
-    qemu_mod_timer(s->second_timer2, s->next_second_time);
     rtc_timer_update(s, now);
 #ifdef TARGET_I386
     if (s->lost_tick_policy == LOST_TICK_SLEW) {
@@ -604,6 +535,8 @@  static void rtc_get_date(Object *obj, Visitor *v, void *opaque,
     ISADevice *isa = ISA_DEVICE(obj);
     RTCState *s = DO_UPCAST(RTCState, dev, isa);

+    rtc_calibrate_time(s);
+    rtc_set_cmos(s);
     visit_start_struct(v, NULL, "struct tm", name, 0, errp);
     visit_type_int32(v, &s->current_tm.tm_year, "tm_year", errp);
     visit_type_int32(v, &s->current_tm.tm_mon, "tm_mon", errp);
@@ -640,8 +573,6 @@  static int rtc_initfn(ISADevice *dev)
 #endif

     s->periodic_timer = qemu_new_timer_ns(rtc_clock, rtc_periodic_timer, s);
-    s->second_timer = qemu_new_timer_ns(rtc_clock, rtc_update_second, s);
-    s->second_timer2 = qemu_new_timer_ns(rtc_clock, rtc_update_second2, s);

     s->clock_reset_notifier.notify = rtc_notify_clock_reset;
     qemu_register_clock_reset_notifier(rtc_clock, &s->clock_reset_notifier);
@@ -649,10 +580,6 @@  static int rtc_initfn(ISADevice *dev)
     s->suspend_notifier.notify = rtc_notify_suspend;
     qemu_register_suspend_notifier(&s->suspend_notifier);

-    s->next_second_time =
-        qemu_get_clock_ns(rtc_clock) + (get_ticks_per_sec() * 99) / 100;
-    qemu_mod_timer(s->second_timer2, s->next_second_time);
-
     memory_region_init_io(&s->io, &cmos_ops, s, "rtc", 2);
     isa_register_ioport(dev, &s->io, base);

diff --git a/qemu-timer.h b/qemu-timer.h
index f8af595..9310f90 100644
--- a/qemu-timer.h
+++ b/qemu-timer.h
@@ -84,6 +84,11 @@  static inline int64_t qemu_get_clock_ms(QEMUClock *clock)
     return qemu_get_clock_ns(clock) / SCALE_MS;
 }

+static inline int64_t qemu_get_clock_us(QEMUClock *clock)
+{
+    return qemu_get_clock_ns(clock) / SCALE_US;
+}
+
 static inline int64_t get_ticks_per_sec(void)
 {
     return 1000000000LL;