sched/sched: add hrtimer support to drive the scheduler

Add hrtimer support to drive the scheduler.

Signed-off-by: Chengdong Wang <wangchengdong@lixiang.com>

drivers/timers/arch_alarm.c

@@ -126,7 +126,7 @@ static void ndelay_accurate(unsigned long nanoseconds)
 static void oneshot_callback(FAR struct oneshot_lowerhalf_s *lower,
                              FAR void *arg)
 {
-#ifdef CONFIG_SCHED_TICKLESS
+#if defined(CONFIG_SCHED_TICKLESS) || defined(CONFIG_HRTIMER)
   nxsched_process_timer();
 #else
   clock_t now;
@@ -388,7 +388,7 @@ int weak_function up_alarm_tick_cancel(FAR clock_t *ticks)
  *
  ****************************************************************************/
 
-#ifdef CONFIG_SCHED_TICKLESS
+#if defined(CONFIG_SCHED_TICKLESS) || defined(CONFIG_HRTIMER)
 int weak_function up_alarm_start(FAR const struct timespec *ts)
 {
   int ret = -EAGAIN;

include/nuttx/arch.h

@@ -2051,7 +2051,8 @@ 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

sched/sched/sched_timer.c

@@ -31,6 +31,82 @@
 #include <errno.h>
 
 #include "sched/sched.h"
+#include "hrtimer/hrtimer.h"
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+/* High-resolution timer used to drive the scheduler tick.
+ *
+ * In non-tickless mode, this timer periodically generates a scheduler
+ * tick with interval NSEC_PER_TICK.
+ *
+ * In tickless mode, the timer is still used, but the callback does not
+ * request automatic re-arming.
+ */
+
+#ifdef CONFIG_HRTIMER
+static hrtimer_t g_sched_hrtimer;
+static bool g_sched_hrtimer_started = false;
+#endif
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: nxsched_hrtimer_callback
+ *
+ * Description:
+ *   High-resolution timer callback used to drive the scheduler.
+ *
+ *   This callback is invoked when the scheduler hrtimer expires.
+ *   It advances the scheduler time base by calling
+ *   nxsched_process_tick().
+ *
+ * Input Parameters:
+ *   hrtimer - Pointer to the expired hrtimer instance
+ *   expired - Expiration time in nanoseconds
+ *
+ * Returned Value:
+ *   In non-tickless mode:
+ *     Returns the next expiration interval (NSEC_PER_TICK),
+ *     causing the hrtimer to be re-armed periodically.
+ *
+ *   In tickless mode:
+ *     Returns 0 to indicate that the timer should not be
+ *     automatically restarted.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_HRTIMER
+static uint64_t
+nxsched_hrtimer_callback(FAR const struct hrtimer_s *hrtimer,
+                         uint64_t expired)
+{
+  UNUSED(hrtimer);
+  UNUSED(expired);
+
+  /* Advance scheduler time and process time slice expiration */
+
+  nxsched_process_tick();
+
+#ifndef CONFIG_SCHED_TICKLESS
+  /* Periodic tick mode: re-arm timer with fixed tick interval */
+
+  return NSEC_PER_TICK;
+#else
+  /* Tickless mode controls the next wakeup explicitly */
+
+  return 0;
+#endif
+}
+#endif
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
 
 /****************************************************************************
  * Name: nxsched_process_timer
@@ -47,5 +123,22 @@
 
 void nxsched_process_timer(void)
 {
+#ifdef CONFIG_HRTIMER
+  /* Process all expired high-resolution timers */
+
+  if (g_sched_hrtimer_started == false)
+    {
+      g_sched_hrtimer_started = true;
+      hrtimer_start(&g_sched_hrtimer,
+                    nxsched_hrtimer_callback,
+                    NSEC_PER_TICK,
+                    HRTIMER_MODE_REL);
+    }
+
+  hrtimer_process(hrtimer_gettime());
+#else
+  /* Fallback: process one scheduler tick */
+
   nxsched_process_tick();
+#endif
 }