[PATCH 5/7] hw/rtc/m48t59: Reduce timer precision to milli-second

[Philippe Mathieu-Daudé]

The current implementation uses nano-second precision,
while the RTC can not be more precise than a milli-second.
Simplify by using a milli-second based timer.
Rename the timer 'alrm_timer_ms' to have the unit explicit.

Inspired-by: Mark Cave-Ayland <mark.cave-ayl...@ilande.co.uk>
Signed-off-by: Philippe Mathieu-Daudé <f4...@amsat.org>
---
 hw/rtc/m48t59-internal.h |  2 +-
 hw/rtc/m48t59.c          | 31 ++++++++++++++++---------------
 2 files changed, 17 insertions(+), 16 deletions(-)

diff --git a/hw/rtc/m48t59-internal.h b/hw/rtc/m48t59-internal.h
index cd648241e9..f21b603f97 100644
--- a/hw/rtc/m48t59-internal.h
+++ b/hw/rtc/m48t59-internal.h
@@ -49,7 +49,7 @@ typedef struct M48t59State {
     time_t   stop_time;
     /* Alarm & watchdog */
     struct tm alarm;
-    QEMUTimer *alrm_timer;
+    QEMUTimer *alrm_timer_ms;
     QEMUTimer *wd_timer;
     /* NVRAM storage */
     uint8_t *buffer;
diff --git a/hw/rtc/m48t59.c b/hw/rtc/m48t59.c
index 47d48054fd..d2717d00a9 100644
--- a/hw/rtc/m48t59.c
+++ b/hw/rtc/m48t59.c
@@ -89,7 +89,7 @@ static M48txxInfo m48txx_sysbus_info[] = {
 static void alarm_cb (void *opaque)
 {
     struct tm tm;
-    uint64_t next_time;
+    uint64_t next_time_s;
     M48t59State *NVRAM = opaque;
 
     qemu_set_irq(NVRAM->IRQ, 1);
@@ -104,42 +104,43 @@ static void alarm_cb (void *opaque)
             tm.tm_mon = 1;
             tm.tm_year++;
         }
-        next_time = qemu_timedate_diff(&tm) - NVRAM->time_offset;
+        next_time_s = qemu_timedate_diff(&tm) - NVRAM->time_offset;
     } else if ((NVRAM->buffer[0x1FF5] & 0x80) != 0 &&
               (NVRAM->buffer[0x1FF4] & 0x80) == 0 &&
               (NVRAM->buffer[0x1FF3] & 0x80) == 0 &&
               (NVRAM->buffer[0x1FF2] & 0x80) == 0) {
         /* Repeat once a day */
-        next_time = 24 * 60 * 60;
+        next_time_s = 24 * 60 * 60;
     } else if ((NVRAM->buffer[0x1FF5] & 0x80) != 0 &&
               (NVRAM->buffer[0x1FF4] & 0x80) != 0 &&
               (NVRAM->buffer[0x1FF3] & 0x80) == 0 &&
               (NVRAM->buffer[0x1FF2] & 0x80) == 0) {
         /* Repeat once an hour */
-        next_time = 60 * 60;
+        next_time_s = 60 * 60;
     } else if ((NVRAM->buffer[0x1FF5] & 0x80) != 0 &&
               (NVRAM->buffer[0x1FF4] & 0x80) != 0 &&
               (NVRAM->buffer[0x1FF3] & 0x80) != 0 &&
               (NVRAM->buffer[0x1FF2] & 0x80) == 0) {
         /* Repeat once a minute */
-        next_time = 60;
+        next_time_s = 60;
     } else {
         /* Repeat once a second */
-        next_time = 1;
+        next_time_s = 1;
     }
-    timer_mod(NVRAM->alrm_timer, qemu_clock_get_ns(rtc_clock) +
-                    next_time * 1000);
+    timer_mod(NVRAM->alrm_timer_ms,
+              qemu_clock_get_ms(rtc_clock) + next_time_s *
+                                             NANOSECONDS_PER_SECOND / 
SCALE_MS);
     qemu_set_irq(NVRAM->IRQ, 0);
 }
 
 static void set_alarm(M48t59State *NVRAM)
 {
     int diff;
-    if (NVRAM->alrm_timer != NULL) {
-        timer_del(NVRAM->alrm_timer);
+    if (NVRAM->alrm_timer_ms != NULL) {
+        timer_del(NVRAM->alrm_timer_ms);
         diff = qemu_timedate_diff(&NVRAM->alarm) - NVRAM->time_offset;
         if (diff > 0)
-            timer_mod(NVRAM->alrm_timer, diff * 1000);
+            timer_mod(NVRAM->alrm_timer_ms, diff * 1000);
     }
 }
 
@@ -539,9 +540,9 @@ void m48t59_reset_common(M48t59State *NVRAM)
 {
     NVRAM->addr = 0;
     NVRAM->lock = 0;
-    if (NVRAM->alrm_timer != NULL)
-        timer_del(NVRAM->alrm_timer);
-
+    if (NVRAM->alrm_timer_ms != NULL) {
+        timer_del(NVRAM->alrm_timer_ms);
+    }
     if (NVRAM->wd_timer != NULL)
         timer_del(NVRAM->wd_timer);
 }
@@ -603,7 +604,7 @@ void m48t59_realize_common(M48t59State *s, Error **errp)
 {
     s->buffer = g_malloc0(s->size);
     if (s->model == 59) {
-        s->alrm_timer = timer_new_ns(rtc_clock, &alarm_cb, s);
+        s->alrm_timer_ms = timer_new_ms(rtc_clock, &alarm_cb, s);
         s->wd_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, &watchdog_cb, s);
     }
     qemu_get_timedate(&s->alarm, 0);
-- 
2.21.3