Add mcu/*stm32l4.

mcu/chx-stm32l4.c

@@ -0,0 +1,29 @@
+#include <stdint.h>
+#include <mcu/cortex-m.h>
+#include <mcu/stm32l.h>
+
+extern int chx_allow_sleep;
+
+void
+chx_sleep_mode (int how)
+{
+  /*TBD*/
+  (void)how;
+}
+
+void __attribute__((naked))
+chx_idle (void)
+{
+  /*TBD*/
+  int sleep_enabled;
+
+  for (;;)
+    {
+      asm ("ldr	%0, %1" : "=r" (sleep_enabled): "m" (chx_allow_sleep));
+      if (sleep_enabled)
+	{
+	  asm volatile ("wfi" : : : "memory");
+	  /* NOTE: it never comes here.  Don't add lines after this.  */
+	}
+    }
+}