sys/ztimer: add xtimer_on_ztimer

This commit adds logic to make xtimer use ztimer_usec as backend
(instead of periph_timer). This allows ztimer_usec and xtimer to
coexist. It also allows xtimer to profit from eventually implemented
power mode blocking in ztimer's periph_timer backend.

Makefile.dep

@@ -675,14 +675,6 @@ ifneq (,$(filter arduino_pwm,$(FEATURES_USED)))
   FEATURES_REQUIRED += periph_pwm
 endif
 
-ifneq (,$(filter xtimer,$(USEMODULE)))
-  ifeq (,$(filter ztimer_xtimer_compat,$(USEMODULE)))
-    DEFAULT_MODULE += auto_init_xtimer
-    FEATURES_REQUIRED += periph_timer
-    USEMODULE += div
-  endif
-endif
-
 ifneq (,$(filter saul,$(USEMODULE)))
   USEMODULE += phydat
 endif
@@ -1015,10 +1007,28 @@ ifneq (,$(filter periph_uart_nonblocking,$(USEMODULE)))
   FEATURES_REQUIRED += periph_uart
 endif
 
+# include ztimer dependencies
 ifneq (,$(filter ztimer%,$(USEMODULE)))
   include $(RIOTBASE)/sys/ztimer/Makefile.dep
 endif
 
+# handle xtimer's deps. Needs to be done *after* ztimer
+ifneq (,$(filter xtimer,$(USEMODULE)))
+  ifeq (,$(filter ztimer_xtimer_compat,$(USEMODULE)))
+    # xtimer is used, ztimer xtimer wrapper is not
+    DEFAULT_MODULE += auto_init_xtimer
+    USEMODULE += div
+    ifeq (,$(filter xtimer_on_ztimer,$(USEMODULE)))
+      # ztimer is not used, so use *periph_timer as low-level timer*.
+      FEATURES_REQUIRED += periph_timer
+    else
+      # will use *ztimer_usec as low-level timer*
+    endif
+  else
+  # ztimer_xtimer_compat is used, all of *xtimer's API will be mapped on ztimer.*
+  endif
+endif
+
 # Enable periph_gpio when periph_gpio_irq is enabled
 ifneq (,$(filter periph_gpio_irq,$(USEMODULE)))
   FEATURES_REQUIRED += periph_gpio

sys/include/xtimer.h

@@ -42,8 +42,10 @@
 #include "ztimer/xtimer_compat.h"
 #else
 
+#ifndef MODULE_XTIMER_ON_ZTIMER
 #include "board.h"
 #include "periph_conf.h"
+#endif
 
 #ifdef __cplusplus
 extern "C" {

sys/include/xtimer/implementation.h

@@ -27,9 +27,15 @@
 #error "Do not include this file directly! Use xtimer.h instead"
 #endif
 
+#ifdef MODULE_XTIMER_ON_ZTIMER
+#include "ztimer.h"
+#else
 #include "periph/timer.h"
+#endif
+
 #include "irq.h"
 
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -46,7 +52,12 @@ extern volatile uint64_t _xtimer_current_time;
  */
 static inline uint32_t _xtimer_lltimer_now(void)
 {
+#ifndef MODULE_XTIMER_ON_ZTIMER
     return timer_read(XTIMER_DEV);
+#else
+    return ztimer_now(ZTIMER_USEC);
+#endif
+
 }
 
 /**

sys/xtimer/xtimer_core.c

@@ -24,9 +24,12 @@
 
 #include <stdint.h>
 #include <string.h>
+
+#ifndef MODULE_XTIMER_ON_ZTIMER
 #include "board.h"
 #include "periph/timer.h"
 #include "periph_conf.h"
+#endif
 
 #include "xtimer.h"
 #include "irq.h"
@@ -50,12 +53,20 @@ static inline void _update_long_timers(uint64_t *now);
 static inline void _schedule_earliest_lltimer(uint32_t now);
 
 static void _timer_callback(void);
+
+#ifndef MODULE_XTIMER_ON_ZTIMER
 static void _periph_timer_callback(void *arg, int chan);
+#else
+static void _ztimer_callback(void *arg);
+static ztimer_t _ztimer = { .callback=_ztimer_callback };
+#endif
 
 void xtimer_init(void)
 {
+#ifndef MODULE_XTIMER_ON_ZTIMER
     /* initialize low-level timer */
     timer_init(XTIMER_DEV, XTIMER_HZ, _periph_timer_callback, NULL);
+#endif
 
     /* register initial overflow tick */
     _schedule_earliest_lltimer(_xtimer_now());
@@ -107,12 +118,20 @@ void _xtimer_set64(xtimer_t *timer, uint32_t offset, uint32_t long_offset)
     irq_restore(state);
 }
 
+#ifndef MODULE_XTIMER_ON_ZTIMER
 static void _periph_timer_callback(void *arg, int chan)
 {
     (void)arg;
     (void)chan;
     _timer_callback();
 }
+#else
+static void _ztimer_callback(void *arg)
+{
+    (void)arg;
+    _timer_callback();
+}
+#endif
 
 static void _shoot(xtimer_t *timer)
 {
@@ -141,7 +160,11 @@ static inline void _schedule_earliest_lltimer(uint32_t now)
     }
 
     DEBUG("_schedule_earliest_lltimer(): setting %" PRIu32 "\n", _xtimer_lltimer_mask(target));
+#ifndef MODULE_XTIMER_ON_ZTIMER
     timer_set_absolute(XTIMER_DEV, XTIMER_CHAN, _xtimer_lltimer_mask(target));
+#else
+    ztimer_set(ZTIMER_USEC, &_ztimer, target - ztimer_now(ZTIMER_USEC));
+#endif
     _lltimer_ongoing = true;
 }
 

sys/ztimer/Makefile.dep

@@ -2,7 +2,6 @@
 # ztimer dependencies
 #
 
-
 # "ztimer" is the default meta-module of ztimer
 ifneq (,$(filter ztimer,$(USEMODULE)))
   USEMODULE += ztimer_core
@@ -24,8 +23,23 @@ ifneq (,$(filter ztimer,$(USEMODULE)))
   endif
 endif
 
+# unless ztimer_xtimer_compat is used, make xtimer use ztimer as backend.
+ifneq (,$(filter ztimer,$(USEMODULE)))
+  ifneq  (,$(filter xtimer,$(USEMODULE)))
+    ifeq (,$(filter ztimer_xtimer_compat,$(USEMODULE)))
+        USEMODULE += xtimer_on_ztimer
+    endif
+  endif
+endif
+
+# make xtimer use ztimer_usec as low level timer
+ifneq (,$(filter xtimer_on_ztimer,$(USEMODULE)))
+  USEMODULE += ztimer_usec
+  PSEUDOMODULES += xtimer_on_ztimer
+endif
+
 # "ztimer_xtimer_compat" is a wrapper of the xtimer API on ztimer_used
-# (it is currently incomplete)
+# (it is currently incomplete). Unless doing testing, use "xtimer_on_ztimer".
 ifneq (,$(filter ztimer_xtimer_compat,$(USEMODULE)))
   USEMODULE += div
   USEMODULE += ztimer_usec
@@ -41,11 +55,11 @@ ifneq (,$(filter ztimer_convert_%,$(USEMODULE)))
   USEMODULE += ztimer_convert
 endif
 
-ifneq (,$(filter ztimer_periph,$(USEMODULE)))
+ifneq (,$(filter ztimer_periph_timer,$(USEMODULE)))
   FEATURES_REQUIRED += periph_timer
 endif
 
-ifneq (,$(filter ztimer_rtt,$(USEMODULE)))
+ifneq (,$(filter ztimer_periph_rtt,$(USEMODULE)))
   FEATURES_REQUIRED += periph_rtt
 endif
 
@@ -55,7 +69,7 @@ endif
 
 ifneq (,$(filter ztimer_usec,$(USEMODULE)))
   USEMODULE += ztimer
-  USEMODULE += ztimer_periph
+  USEMODULE += ztimer_periph_timer
 endif
 
 ifneq (,$(filter ztimer_msec,$(USEMODULE)))