The CONFIG_SYSTEMTICK_EXTCLK selection should only be available on systems that support it

arch/Kconfig

@@ -145,6 +145,10 @@ config ARCH_NAND_HWECC
 	bool
 	default n
 
+config ARCH_HAVE_EXTCLK
+	bool
+	default n
+
 menuconfig PAGING
 	bool "On-demand paging"
 	default n

arch/arm/src/sam34/Kconfig

@@ -1199,6 +1199,7 @@ endmenu # USB Full Speed Device Controller driver (DCD) options
 config SAM34_TC
 	bool
 	default n
+	select ARCH_HAVE_EXTCLK
 
 menu "AT91SAM3/4 Timer/Counter options"
 	depends on SAM34_TC

configs/sam4s-xplained-pro/nsh/defconfig

@@ -297,6 +297,7 @@ CONFIG_ARCH_HAVE_IRQPRIO=y
 CONFIG_ARCH_HAVE_VFORK=y
 # CONFIG_ARCH_HAVE_MMU is not set
 # CONFIG_ARCH_NAND_HWECC is not set
+CONFIG_ARCH_HAVE_EXTCLK=y
 # CONFIG_ARCH_IRQPRIO is not set
 CONFIG_ARCH_STACKDUMP=y
 # CONFIG_ENDIAN_BIG is not set

sched/Kconfig

@@ -64,6 +64,7 @@ config MSEC_PER_TICK
 config SYSTEMTICK_EXTCLK
 	bool "Use external clock"
 	default n
+	depends on ARCH_HAVE_EXTCLK
 	---help---
 		Use external clock for system tick. When enabled, the platform-specific
 		logic must start it's own timer interrupt to make periodic calls to the