From 73e22612e218e1817c9eb8e28a72a40e861bcc99 Mon Sep 17 00:00:00 2001
From: Juergen Fitschen <me@jue.yt>
Date: Thu, 26 Mar 2020 10:56:10 +0100
Subject: [PATCH] sys/ztimer: add power management for ztimer clocks

---
 sys/include/ztimer.h   |  8 ++++++++
 sys/ztimer/auto_init.c | 18 ++++++++++++++++++
 sys/ztimer/core.c      | 23 +++++++++++++++++++++++
 3 files changed, 49 insertions(+)

diff --git a/sys/include/ztimer.h b/sys/include/ztimer.h
index 096310801e..37dd23a3a6 100644
--- a/sys/include/ztimer.h
+++ b/sys/include/ztimer.h
@@ -223,6 +223,11 @@
 extern "C" {
 #endif
 
+/**
+ * @brief   Disables interaction with pm_layered for a clock
+ */
+#define ZTIMER_CLOCK_NO_REQUIRED_PM_MODE (UINT8_MAX)
+
 /**
  * @brief ztimer_base_t forward declaration
  */
@@ -297,6 +302,9 @@ struct ztimer_clock {
     uint32_t lower_last;            /**< timer value at last now() call     */
     ztimer_now_t checkpoint;        /**< cumulated time at last now() call  */
 #endif
+#if MODULE_PM_LAYERED || DOXYGEN
+    uint8_t required_pm_mode;       /**< min. pm mode required for the clock to run */
+#endif
 };
 
 /**
diff --git a/sys/ztimer/auto_init.c b/sys/ztimer/auto_init.c
index 456e68d09d..7c4b264c17 100644
--- a/sys/ztimer/auto_init.c
+++ b/sys/ztimer/auto_init.c
@@ -86,6 +86,14 @@
 #define CONFIG_ZTIMER_USEC_WIDTH (32)
 #endif
 
+#ifndef CONFIG_ZTIMER_USEC_REQUIRED_PM_MODE
+#define CONFIG_ZTIMER_USEC_REQUIRED_PM_MODE ZTIMER_CLOCK_NO_REQUIRED_PM_MODE
+#endif
+
+#ifndef CONFIG_ZTIMER_MSEC_REQUIRED_PM_MODE
+#define CONFIG_ZTIMER_MSEC_REQUIRED_PM_MODE ZTIMER_CLOCK_NO_REQUIRED_PM_MODE
+#endif
+
 #if MODULE_ZTIMER_USEC
 #  if CONFIG_ZTIMER_USEC_TYPE_PERIPH_TIMER
 static ztimer_periph_timer_t _ztimer_periph_timer_usec = { .min = CONFIG_ZTIMER_USEC_MIN };
@@ -160,6 +168,11 @@ void ztimer_init(void)
             CONFIG_ZTIMER_USEC_ADJUST);
     ZTIMER_USEC->adjust = CONFIG_ZTIMER_USEC_ADJUST;
 #  endif
+#  ifdef MODULE_PM_LAYERED
+    LOG_DEBUG("ztimer_init(): ZTIMER_USEC setting required_pm_mode to %i\n",
+            CONFIG_ZTIMER_USEC_REQUIRED_PM_MODE);
+    ZTIMER_USEC->required_pm_mode = CONFIG_ZTIMER_USEC_REQUIRED_PM_MODE;
+#  endif
 #endif
 
 #ifdef ZTIMER_RTT_INIT
@@ -180,5 +193,10 @@ void ztimer_init(void)
             CONFIG_ZTIMER_MSEC_ADJUST);
     ZTIMER_MSEC->adjust = CONFIG_ZTIMER_MSEC_ADJUST;
 #  endif
+#  ifdef MODULE_PM_LAYERED
+    LOG_DEBUG("ztimer_init(): ZTIMER_MSEC setting required_pm_mode to %i\n",
+            CONFIG_ZTIMER_MSEC_REQUIRED_PM_MODE);
+    ZTIMER_MSEC->required_pm_mode = CONFIG_ZTIMER_MSEC_REQUIRED_PM_MODE;
+#  endif
 #endif
 }
diff --git a/sys/ztimer/core.c b/sys/ztimer/core.c
index 736fbc31d5..45e143a206 100644
--- a/sys/ztimer/core.c
+++ b/sys/ztimer/core.c
@@ -27,6 +27,9 @@
 
 #include "kernel_defines.h"
 #include "irq.h"
+#ifdef MODULE_PM_LAYERED
+#include "pm_layered.h"
+#endif
 #include "ztimer.h"
 
 #define ENABLE_DEBUG (0)
@@ -106,6 +109,13 @@ static void _add_entry_to_list(ztimer_clock_t *clock, ztimer_base_t *entry)
 
     ztimer_base_t *list = &clock->list;
 
+#ifdef MODULE_PM_LAYERED
+    /* First timer on the clock's linked list */
+    if (list->next == NULL && clock->required_pm_mode != ZTIMER_CLOCK_NO_REQUIRED_PM_MODE) {
+        pm_block(clock->required_pm_mode);
+    }
+#endif
+
     /* Jump past all entries which are set to an earlier target than the new entry */
     while (list->next) {
         ztimer_base_t *list_entry = list->next;
@@ -223,6 +233,13 @@ static void _del_entry_from_list(ztimer_clock_t *clock, ztimer_base_t *entry)
         }
         list = list->next;
     }
+
+#ifdef MODULE_PM_LAYERED
+    /* The last timer just got removed from the clock's linked list */
+    if (clock->list.next == NULL && clock->required_pm_mode != ZTIMER_CLOCK_NO_REQUIRED_PM_MODE) {
+        pm_unblock(clock->required_pm_mode);
+    }
+#endif
 }
 
 static ztimer_t *_now_next(ztimer_clock_t *clock)
@@ -232,7 +249,13 @@ static ztimer_t *_now_next(ztimer_clock_t *clock)
     if (entry && (entry->offset == 0)) {
         clock->list.next = entry->next;
         if (!entry->next) {
+            /* The last timer just got removed from the clock's linked list */
             clock->last = NULL;
+#ifdef MODULE_PM_LAYERED
+            if (clock->required_pm_mode != ZTIMER_CLOCK_NO_REQUIRED_PM_MODE) {
+                pm_unblock(clock->required_pm_mode);
+            }
+#endif
         }
         return (ztimer_t*)entry;
     }