drivers/kconfig: simplify shared rtt/rtc hardware in kconfig

cpu/efm32/Kconfig

@@ -16,6 +16,7 @@ config CPU_COMMON_EFM32
     select HAS_PERIPH_RTT_SET_COUNTER
     select HAS_PERIPH_RTT_OVERFLOW
     select HAS_PERIPH_WDT
+    select HAVE_SHARED_PERIPH_RTT_PERIPH_RTC
 
 config CPU_EFM32_SERIES0
     bool
@@ -45,9 +46,5 @@ config HAS_EFM32_CORETEMP
 config CPU
     default "efm32" if CPU_COMMON_EFM32
 
-config ERROR_MODULES_CONFLICT
-    default "On the EFM32, the RTC and RTT map to the same hardware peripheral." if MODULE_PERIPH_RTC && MODULE_PERIPH_RTT
-    depends on CPU_COMMON_EFM32
-
 orsource "families/*/Kconfig"
 source "$(RIOTCPU)/cortexm_common/Kconfig"

cpu/sam0_common/Kconfig

@@ -25,14 +25,12 @@ config CPU_COMMON_SAM0
     select HAS_PERIPH_WDT
     select HAS_PERIPH_WDT_CB
     select HAS_PERIPH_WDT_WARNING_PERIOD
+    select HAVE_SHARED_PERIPH_RTT_PERIPH_RTC
 
 if CPU_COMMON_SAM0
 
 rsource "periph/Kconfig"
 
-config ERROR_MODULES_CONFLICT
-    default "On SAM0, the RTC and RTT map to the same hardware peripheral." if MODULE_PERIPH_RTC && MODULE_PERIPH_RTT
-
 endif # CPU_COMMON_SAM0
 
 source "$(RIOTCPU)/cortexm_common/Kconfig"

cpu/stm32/kconfigs/f1/Kconfig

@@ -17,15 +17,13 @@ config CPU_FAM_F1
     select HAS_PERIPH_FLASHPAGE_RAW
     select HAS_PERIPH_RTT_SET_COUNTER
     select HAS_PERIPH_WDT
+    select HAVE_SHARED_PERIPH_RTT_PERIPH_RTC
 
 if CPU_FAM_F1
 
 config CPU_FAM
     default "f1"
 
-config ERROR_MODULES_CONFLICT
-    default "On STM32F1, the RTC and RTT map to the same hardware peripheral." if MODULE_PERIPH_RTC && MODULE_PERIPH_RTT
-
 endif # CPU_FAM_F1
 
 config HAS_CPU_STM32F1

drivers/periph_common/Kconfig

@@ -162,5 +162,11 @@ config MODULE_PERIPH_INIT_USBDEV
 
 endif # TEST_KCONFIG
 
+config HAVE_SHARED_PERIPH_RTT_PERIPH_RTC
+    bool
+    help
+        The periph_rtc module or the periph_rtt module share hardware, thus,
+        only one can be selected.
+
 rsource "Kconfig.timer"
 rsource "Kconfig.wdt"

kconfigs/Kconfig.errors

@@ -15,6 +15,7 @@
 
 config ERROR_MODULES_CONFLICT
     string
+    default "The RTC and RTT map to the same hardware peripheral." if MODULE_PERIPH_RTC && MODULE_PERIPH_RTT && HAVE_SHARED_PERIPH_RTT_PERIPH_RTC
     help
         Used to indicate that conflicting modules (i.e. modules that can't be
         active at the same time) are being used together.

sys/ztimer/Kconfig

@@ -75,8 +75,7 @@ choice
     bool "Backend"
     depends on MODULE_ZTIMER_SEC
     default ZTIMER_SEC_BACKEND_RTC if !BOARD_NATIVE && \
-                                      !CPU_COMMON_SAM0 && \
-                                      !CPU_COMMON_EFM32
+                                      !HAVE_SHARED_PERIPH_RTT_PERIPH_RTC
     default ZTIMER_SEC_BACKEND_RTT
 
 config ZTIMER_SEC_BACKEND_TIMER