From a483c884cec057b4bfa5e3ee78fb17224c3becbf Mon Sep 17 00:00:00 2001
From: ouyangxiangzhen <ouyangxiangzhen@xiaomi.com>
Date: Tue, 18 Jun 2024 20:25:50 +0800
Subject: [PATCH] sched/timer: Fix timer accuracy problems

This commit fixed timer accuracy problems when repetitive timer is set.

Signed-off-by: ouyangxiangzhen <ouyangxiangzhen@xiaomi.com>
---
 sched/timer/timer.h            |  4 ++-
 sched/timer/timer_create.c     |  1 +
 sched/timer/timer_getoverrun.c | 15 ++++++++--
 sched/timer/timer_settime.c    | 55 +++++++++++++++++-----------------
 4 files changed, 43 insertions(+), 32 deletions(-)

diff --git a/sched/timer/timer.h b/sched/timer/timer.h
index 49e9b7f990..f91bbff2b8 100644
--- a/sched/timer/timer.h
+++ b/sched/timer/timer.h
@@ -58,7 +58,9 @@ struct posix_timer_s
   uint8_t          pt_flags;       /* See PT_FLAGS_* definitions */
   uint8_t          pt_crefs;       /* Reference count */
   pid_t            pt_owner;       /* Creator of timer */
-  int              pt_delay;       /* If non-zero, used to reset repetitive timers */
+  int              pt_overrun;     /* Overrun time */
+  sclock_t         pt_delay;       /* If non-zero, used to reset repetitive timers */
+  clock_t          pt_expected;    /* Expected absolute time */
   struct wdog_s    pt_wdog;        /* The watchdog that provides the timing */
   struct sigevent  pt_event;       /* Notification information */
   struct sigwork_s pt_work;
diff --git a/sched/timer/timer_create.c b/sched/timer/timer_create.c
index 7e31a1213e..1aa1fbe95b 100644
--- a/sched/timer/timer_create.c
+++ b/sched/timer/timer_create.c
@@ -183,6 +183,7 @@ int timer_create(clockid_t clockid, FAR struct sigevent *evp,
   ret->pt_crefs = 1;
   ret->pt_owner = nxsched_getpid();
   ret->pt_delay = 0;
+  ret->pt_expected = 0;
 
   /* Was a struct sigevent provided? */
 
diff --git a/sched/timer/timer_getoverrun.c b/sched/timer/timer_getoverrun.c
index 0ad2f98031..6fe13b20ac 100644
--- a/sched/timer/timer_getoverrun.c
+++ b/sched/timer/timer_getoverrun.c
@@ -77,9 +77,18 @@
 
 int timer_getoverrun(timer_t timerid)
 {
-  UNUSED(timerid);
-  set_errno(EINVAL);
-  return ERROR;
+  FAR struct posix_timer_s *timer = timer_gethandle(timerid);
+  int ret;
+
+  if (!timer)
+    {
+      set_errno(EINVAL);
+      return ERROR;
+    }
+
+  ret = timer->pt_overrun;
+
+  return ret > DELAYTIMER_MAX ? DELAYTIMER_MAX : ret;
 }
 
 #endif /* CONFIG_DISABLE_POSIX_TIMERS */
diff --git a/sched/timer/timer_settime.c b/sched/timer/timer_settime.c
index b0a386bc67..866d8d58bd 100644
--- a/sched/timer/timer_settime.c
+++ b/sched/timer/timer_settime.c
@@ -96,11 +96,32 @@ static inline void timer_signotify(FAR struct posix_timer_s *timer)
 static inline void timer_restart(FAR struct posix_timer_s *timer,
                                  wdparm_t itimer)
 {
+  clock_t ticks;
+  sclock_t delay;
+
   /* If this is a repetitive timer, then restart the watchdog */
 
   if (timer->pt_delay)
     {
-      wd_start(&timer->pt_wdog, timer->pt_delay, timer_timeout, itimer);
+      /* Check whether next expected time is reached */
+
+      ticks = clock_systime_ticks();
+      timer->pt_overrun = 0;
+
+      for (; ; )
+        {
+          timer->pt_expected += timer->pt_delay;
+          delay               = timer->pt_expected - ticks;
+          if (delay > 0)
+            {
+              break;
+            }
+
+          timer->pt_overrun++;
+        }
+
+      wd_start_absolute(&timer->pt_wdog, timer->pt_expected,
+                        timer_timeout, itimer);
     }
 }
 
@@ -224,7 +245,6 @@ int timer_settime(timer_t timerid, int flags,
                   FAR struct itimerspec *ovalue)
 {
   FAR struct posix_timer_s *timer = timer_gethandle(timerid);
-  irqstate_t intflags;
   sclock_t delay;
   int ret = OK;
 
@@ -272,29 +292,20 @@ int timer_settime(timer_t timerid, int flags,
   if (value->it_interval.tv_sec > 0 || value->it_interval.tv_nsec > 0)
     {
       delay = clock_time2ticks(&value->it_interval);
-
-      /* REVISIT: Should pt_delay be sclock_t? */
-
-      timer->pt_delay = (int)delay;
+      timer->pt_delay = delay;
     }
   else
     {
       timer->pt_delay = 0;
     }
 
-  /* We need to disable timer interrupts through the following section so
-   * that the system timer is stable.
-   */
-
-  intflags = enter_critical_section();
-
   /* Check if abstime is selected */
 
   if ((flags & TIMER_ABSTIME) != 0)
     {
       /* Calculate a delay corresponding to the absolute time in 'value' */
 
-      clock_abstime2ticks(timer->pt_clock, &value->it_value, &delay);
+      timer->pt_expected = clock_time2ticks(&value->it_value);
     }
   else
     {
@@ -304,25 +315,13 @@ int timer_settime(timer_t timerid, int flags,
        */
 
       delay = clock_time2ticks(&value->it_value);
-    }
-
-  /* If the specified time has already passed, the function shall succeed
-   * and the expiration notification shall be made.
-   */
-
-  if (delay < 0)
-    {
-      delay = 0;
+      timer->pt_expected = clock_systime_ticks() + delay;
     }
 
   /* Then start the watchdog */
 
-  if (delay >= 0)
-    {
-      ret = wd_start(&timer->pt_wdog, delay, timer_timeout, (wdparm_t)timer);
-    }
-
-  leave_critical_section(intflags);
+  ret = wd_start_absolute(&timer->pt_wdog, timer->pt_expected,
+                          timer_timeout, (wdparm_t)timer);
 
   if (ret < 0)
     {