sched/hrtimer: introduce scheduler support with hrtimer

drivers/timers/arch_alarm.c

@@ -118,8 +118,9 @@ static void ndelay_accurate(unsigned long nanoseconds)
 static void oneshot_callback(FAR struct oneshot_lowerhalf_s *lower,
                              FAR void *arg)
 {
-#ifdef CONFIG_SCHED_TICKLESS
-  nxsched_timer_expiration();
+#if defined(CONFIG_HRTIMER) || defined(CONFIG_SCHED_TICKLESS)
+  nxsched_process_timer();
+
 #else
   clock_t now;
 
@@ -380,7 +381,7 @@ int weak_function up_alarm_tick_cancel(FAR clock_t *ticks)
  *
  ****************************************************************************/
 
-#ifdef CONFIG_SCHED_TICKLESS
+#if defined(CONFIG_HRTIMER) || defined(CONFIG_SCHED_TICKLESS)
 int weak_function up_alarm_start(FAR const struct timespec *ts)
 {
   int ret = -EAGAIN;

include/nuttx/arch.h

@@ -2031,7 +2031,8 @@ int up_alarm_tick_cancel(FAR clock_t *ticks);
  *
  ****************************************************************************/
 
-#if defined(CONFIG_SCHED_TICKLESS) && defined(CONFIG_SCHED_TICKLESS_ALARM)
+#if defined(CONFIG_HRTIMER)|| \
+    (defined(CONFIG_SCHED_TICKLESS) && defined(CONFIG_SCHED_TICKLESS_ALARM))
 int up_alarm_start(FAR const struct timespec *ts);
 int up_alarm_tick_start(clock_t ticks);
 #endif
@@ -2461,10 +2462,7 @@ void up_ndelay(unsigned long nanoseconds);
  *
  ****************************************************************************/
 
-#ifndef CONFIG_SCHED_TICKLESS
 void nxsched_process_timer(void);
-#endif
-
 /****************************************************************************
  * Name:  nxsched_timer_expiration
  *

sched/init/nx_start.c

@@ -642,6 +642,10 @@ void nx_start(void)
   timer_initialize();
 #endif
 
+#ifdef CONFIG_HRTIMER
+  nxsched_hrtimer_init();
+#endif
+
   /* Initialize the signal facility (if in link) */
 
   nxsig_initialize();

sched/sched/CMakeLists.txt

@@ -48,7 +48,8 @@ set(SRCS
     sched_sysinfo.c
     sched_get_stateinfo.c
     sched_switchcontext.c
-    sched_sleep.c)
+    sched_sleep.c
+    sched_processtimer.c)
 
 if(DEFINED CONFIG_STACKCHECK_MARGIN)
   if(NOT CONFIG_STACKCHECK_MARGIN EQUAL -1)
@@ -98,8 +99,6 @@ endif()
 
 if(CONFIG_SCHED_TICKLESS)
   list(APPEND SRCS sched_timerexpiration.c)
-else()
-  list(APPEND SRCS sched_processtimer.c)
 endif()
 
 if(CONFIG_SCHED_CRITMONITOR)

sched/sched/Make.defs

@@ -30,7 +30,7 @@ CSRCS += sched_yield.c sched_rrgetinterval.c sched_foreach.c
 CSRCS += sched_lock.c sched_unlock.c sched_lockcount.c
 CSRCS += sched_idletask.c sched_self.c sched_get_stackinfo.c sched_get_tls.c
 CSRCS += sched_sysinfo.c sched_get_stateinfo.c sched_getcpu.c
-CSRCS += sched_switchcontext.c sched_sleep.c
+CSRCS += sched_switchcontext.c sched_sleep.c sched_processtimer.c
 
 ifneq ($(CONFIG_STACKCHECK_MARGIN),)
   ifneq ($(CONFIG_STACKCHECK_MARGIN),-1)
@@ -80,8 +80,6 @@ endif
 
 ifeq ($(CONFIG_SCHED_TICKLESS),y)
 CSRCS += sched_timerexpiration.c
-else
-CSRCS += sched_processtimer.c
 endif
 
 ifeq ($(CONFIG_SCHED_CRITMONITOR),y)

sched/sched/sched.h

@@ -607,4 +607,38 @@ static inline_function int nxsched_select_cpu(cpu_set_t affinity)
   return cpu;
 }
 #  endif
+
+#ifdef CONFIG_HRTIMER
+/****************************************************************************
+ * Name: nxsched_hrtimer_start
+ *
+ * Description:
+ *   (Re)start the scheduler high-resolution timer with a new expiration
+ *   based on the specified tick interval.
+ *
+ * Input Parameters:
+ *   ticks - Number of scheduler ticks until expiration.
+ *
+ * Returned Value:
+ *   Zero on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+int nxsched_hrtimer_start(clock_t ticks);
+
+/****************************************************************************
+ * Name: nxsched_hrtimer_init
+ *
+ * Description:
+ *   Initialize the scheduler high-resolution timer (hrtimer) instance
+ *   and arm the first scheduler timer event.
+ *
+ * Returned Value:
+ *   Zero on success, or a negative errno value on failure.
+ *
+ ****************************************************************************/
+
+int nxsched_hrtimer_init(void);
+#endif
+
 #endif /* __SCHED_SCHED_SCHED_H */

sched/sched/sched_processtimer.c

@@ -44,11 +44,108 @@
 #include "sched/sched.h"
 #include "wdog/wdog.h"
 #include "clock/clock.h"
+#include "hrtimer/hrtimer.h"
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+#ifdef CONFIG_HRTIMER
+
+/* Scheduler-owned high-resolution timer instance.
+ *
+ * This timer acts as the time source for scheduler-related events:
+ *
+ *  - Periodic scheduler ticks in non-tickless mode
+ *  - Dynamic expiration points in tickless mode
+ *
+ * The timer is initialized lazily to avoid unnecessary setup when
+ * CONFIG_HRTIMER is enabled but not used immediately.
+ */
+
+static hrtimer_t g_nxsched_hrtimer;
 
 /****************************************************************************
  * Private Functions
  ****************************************************************************/
 
+static void nxsched_process_tick(void);
+
+/****************************************************************************
+ * Name: nxsched_hrtimer_callback
+ *
+ * Description:
+ *   Callback invoked by the high-resolution timer framework when the
+ *   scheduler timer expires.
+ *
+ *   Behavior depends on scheduler configuration:
+ *
+ *   CONFIG_SCHED_TICKLESS:
+ *     - Query current high-resolution time
+ *     - Convert time to scheduler ticks
+ *     - Notify scheduler via nxsched_tick_expiration()
+ *
+ *   !CONFIG_SCHED_TICKLESS:
+ *     - Re-arm the next periodic tick
+ *     - Process a single scheduler tick
+ *
+ * Input Parameters:
+ *   hrtimer - Pointer to the expired high-resolution timer
+ *
+ * Returned Value:
+ *   In non-tickless mode, returns the interval until the next expiration.
+ *   In tickless mode, the return value is ignored.
+ *
+ ****************************************************************************/
+
+static uint64_t
+nxsched_hrtimer_callback(FAR hrtimer_t *hrtimer, uint64_t expired)
+{
+  UNUSED(hrtimer);
+  UNUSED(expired);
+
+#ifdef CONFIG_SCHED_TICKLESS
+  nxsched_timer_expiration();
+#else
+  nxsched_process_tick();
+  return NSEC_PER_TICK;
+#endif
+}
+
+/****************************************************************************
+ * Name: nxsched_process_hrtimer
+ *
+ * Description:
+ *   Entry point for scheduler-related high-resolution timer processing.
+ *
+ *   Responsibilities:
+ *     - Process expired hrtimer events
+ *     - Perform one-time initialization of the scheduler hrtimer
+ *     - Arm the initial scheduler timer event
+ *
+ *   This function is expected to be called from architecture-specific
+ *   timer interrupt handling code.
+ *
+ * Input Parameters:
+ *   None
+ *
+ * Returned Value:
+ *   None
+ *
+ ****************************************************************************/
+
+static void nxsched_process_hrtimer(void)
+{
+  uint64_t now = hrtimer_gettime();
+
+  /* Process any expired high-resolution timers */
+
+  hrtimer_process(now);
+}
+#endif /* CONFIG_HRTIMER */
+
+#ifndef CONFIG_SCHED_TICKLESS
+
 /****************************************************************************
  * Name:  nxsched_cpu_scheduler
  *
@@ -145,19 +242,7 @@ static inline void nxsched_process_scheduler(void)
 #endif
 
 /****************************************************************************
- * Public Functions
- ****************************************************************************/
-
-/****************************************************************************
- * System Timer Hooks
- *
- * These are standard interfaces that are exported by the OS
- * for use by the architecture specific logic
- *
- ****************************************************************************/
-
-/****************************************************************************
- * Name:  nxsched_process_timer
+ * Name:  nxsched_process_tick
  *
  * Description:
  *   This function handles system timer events.
@@ -174,7 +259,7 @@ static inline void nxsched_process_scheduler(void)
  *
  ****************************************************************************/
 
-void nxsched_process_timer(void)
+static void nxsched_process_tick(void)
 {
 #ifdef CONFIG_CLOCK_TIMEKEEPING
   /* Process wall time */
@@ -204,3 +289,77 @@ void nxsched_process_timer(void)
   board_timerhook();
 #endif
 }
+#endif
+
+#ifdef CONFIG_HRTIMER
+
+/****************************************************************************
+ * Name: nxsched_hrtimer_init
+ *
+ * Description:
+ *   Initialize the scheduler high-resolution timer (hrtimer) instance
+ *   and arm the first scheduler timer event.
+ *
+ * Returned Value:
+ *   Zero on success, or a negative errno value on failure.
+ *
+ ****************************************************************************/
+
+int nxsched_hrtimer_init(void)
+{
+  /* Initialize the scheduler hrtimer instance */
+
+  hrtimer_init(&g_nxsched_hrtimer, nxsched_hrtimer_callback);
+
+  /* Start the first scheduler timer event with one tick interval */
+
+  return hrtimer_start(&g_nxsched_hrtimer, NSEC_PER_TICK, HRTIMER_MODE_REL);
+}
+
+/****************************************************************************
+ * Name: nxsched_hrtimer_start
+ *
+ * Description:
+ *   Start or re-arm the scheduler high-resolution timer.
+ *
+ * Input Parameters:
+ *   ticks - Absolute expiration time
+ *
+ * Returned Value:
+ *   Zero on success, or a negative errno value on failure.
+ *
+ ****************************************************************************/
+
+int nxsched_hrtimer_start(clock_t ticks)
+{
+  return hrtimer_start(&g_nxsched_hrtimer, ticks, HRTIMER_MODE_ABS);
+}
+#endif
+
+/****************************************************************************
+ * System Timer Hooks
+ *
+ * These are standard interfaces that are exported by the OS
+ * for use by the architecture specific logic
+ *
+ ****************************************************************************/
+
+void nxsched_process_timer(void)
+{
+#if defined(CONFIG_HRTIMER)
+  /* High-resolution timer-based scheduling */
+
+  nxsched_process_hrtimer();
+
+#elif defined(CONFIG_SCHED_TICKLESS)
+  /* Legacy tickless scheduling */
+
+  nxsched_timer_expiration();
+
+#else
+  /* Legacy periodic tick-based scheduling */
+
+  nxsched_process_tick();
+
+#endif
+}

sched/sched/sched_timerexpiration.c

@@ -433,7 +433,11 @@ static clock_t nxsched_timer_start(clock_t ticks, clock_t interval)
   if (interval != CLOCK_MAX)
     {
       interval = adjust_next_interval(interval);
+#ifdef CONFIG_HRTIMER
+      nxsched_hrtimer_start(ticks + interval);
+#else
       nxsched_timer_tick_start(ticks, interval);
+#endif
     }
 
   atomic_set(&g_timer_interval, interval);