drivers: timer: improve sys_timer_disable usage

- Remove the weak symbol definition
- Notify about the capability of disabling via a selected Kconfig option
  (CONFIG_SYSTEM_TIMER_HAS_DISABLE_SUPPORT)
- Provide a dummy inline function when the functionality is not
  available

Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>

drivers/timer/Kconfig

@@ -7,13 +7,6 @@
 
 menu "Timer Drivers"
 
-config SYSTEM_CLOCK_DISABLE
-	bool "API to disable system clock"
-	help
-	  This option enables the sys_clock_disable() API in the kernel. It is
-	  needed by some subsystems (which will automatically select it), but is
-	  rarely needed by applications.
-
 config TIMER_HAS_64BIT_CYCLE_COUNTER
 	bool
 	help
@@ -55,6 +48,12 @@ config TICKLESS_CAPABLE
 	  sys_clock_announce() (really, not to produce an interrupt at
 	  all) until the specified expiration.
 
+config SYSTEM_TIMER_HAS_DISABLE_SUPPORT
+	bool
+	help
+	  This option should be selected by drivers implementing support for
+	  sys_clock_disable() API.
+
 source "drivers/timer/Kconfig.altera_avalon"
 source "drivers/timer/Kconfig.apic"
 source "drivers/timer/Kconfig.arcv2"

drivers/timer/Kconfig.cortex_m_systick

@@ -16,6 +16,7 @@ config CORTEX_M_SYSTICK
 		$(dt_compat_enabled,$(DT_COMPAT_ARM_V8M_SYSTICK)) || \
 		$(dt_compat_enabled,$(DT_COMPAT_ARM_V8_1M_SYSTICK))
 	select TICKLESS_CAPABLE
+	select SYSTEM_TIMER_HAS_DISABLE_SUPPORT
 	help
 	  This module implements a kernel device driver for the Cortex-M processor
 	  SYSTICK timer and provides the standard "system clock driver" interfaces.

drivers/timer/Kconfig.mchp_xec_rtos

@@ -7,6 +7,7 @@ config MCHP_XEC_RTOS_TIMER
 	bool "Microchip XEC series RTOS timer"
 	depends on SOC_FAMILY_MEC
 	select TICKLESS_CAPABLE
+	select SYSTEM_TIMER_HAS_DISABLE_SUPPORT
 	help
 	  This module implements a kernel device driver for the Microchip
 	  XEC series RTOS timer and provides the standard "system clock

drivers/timer/Kconfig.mcux_lptmr

@@ -6,6 +6,7 @@
 config MCUX_LPTMR_TIMER
 	bool "MCUX LPTMR timer"
 	depends on HAS_MCUX_LPTMR && !COUNTER_MCUX_LPTMR
+	select SYSTEM_TIMER_HAS_DISABLE_SUPPORT
 	help
 	  This module implements a kernel device driver for the NXP MCUX Low
 	  Power Timer (LPTMR) and provides the standard "system clock driver"

drivers/timer/Kconfig.native_posix

@@ -9,6 +9,7 @@ config NATIVE_POSIX_TIMER
 	depends on BOARD_NATIVE_POSIX
 	select TICKLESS_CAPABLE
 	select TIMER_HAS_64BIT_CYCLE_COUNTER
+	select SYSTEM_TIMER_HAS_DISABLE_SUPPORT
 	help
 	  This module implements a kernel device driver for the native_posix HW timer
 	  model

drivers/timer/native_posix_timer.c

@@ -107,8 +107,6 @@ uint32_t sys_clock_elapsed(void)
 	return (hwm_get_time() - last_tick_time)/tick_period;
 }
 
-
-#if defined(CONFIG_SYSTEM_CLOCK_DISABLE)
 /**
  *
  * @brief Stop announcing sys ticks into the kernel
@@ -122,7 +120,6 @@ void sys_clock_disable(void)
 	irq_disable(TIMER_TICK_IRQ);
 	hwtimer_set_silent_ticks(INT64_MAX);
 }
-#endif /* CONFIG_SYSTEM_CLOCK_DISABLE */
 
 /*
  * @brief Initialize system timer driver

drivers/timer/sys_clock_init.c

@@ -30,7 +30,3 @@ void __weak sys_clock_set_timeout(int32_t ticks, bool idle)
 void __weak sys_clock_idle_exit(void)
 {
 }
-
-void __weak sys_clock_disable(void)
-{
-}

include/drivers/timer/system_timer.h

@@ -108,6 +108,21 @@ extern void sys_clock_announce(int32_t ticks);
  * instantaneous answer.
  */
 extern uint32_t sys_clock_elapsed(void);
+
+#if defined(CONFIG_SYS_CLOCK_EXISTS) && \
+	defined(CONFIG_SYSTEM_TIMER_HAS_DISABLE_SUPPORT) || \
+	defined(__DOXYGEN__)
+/**
+ * @brief Disable system timer.
+ *
+ * This function is a no-op if the system timer does not have the capability
+ * of being disabled.
+ */
+extern void sys_clock_disable(void);
+#else
+static inline void sys_clock_disable(void) {}
+#endif /* CONFIG_SYSTEM_TIMER_HAS_DISABLE_SUPPORT */
+
 /**
  * @}
  */

lib/os/Kconfig

@@ -132,11 +132,10 @@ endif
 
 config REBOOT
 	bool "Reboot functionality"
-	select SYSTEM_CLOCK_DISABLE
 	help
 	  Enable the sys_reboot() API. Enabling this can drag in other subsystems
-	  needed to perform a "safe" reboot (e.g. SYSTEM_CLOCK_DISABLE, to stop the
+	  needed to perform a "safe" reboot (e.g. to stop the system clock before
-	  system clock before issuing a reset).
+	  issuing a reset).
 
 rsource "Kconfig.cbprintf"
 

lib/os/reboot.c

@@ -4,19 +4,17 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
+#include <drivers/timer/system_timer.h>
 #include <sys/reboot.h>
 #include <kernel.h>
 #include <sys/printk.h>
 
 extern void sys_arch_reboot(int type);
-extern void sys_clock_disable(void);
 
 FUNC_NORETURN void sys_reboot(int type)
 {
 	(void)irq_lock();
-#ifdef CONFIG_SYS_CLOCK_EXISTS
 	sys_clock_disable();
-#endif
 
 	sys_arch_reboot(type);