Changes in kernel/arch/arm32/include/arch/asm.h [6ecf5b8:3ee38a9] in mainline

File:

• kernel/arch/arm32/include/arch/asm.h (modified) (2 diffs)

kernel/arch/arm32/include/arch/asm.h

@@ -38 +38 @@
 
 #include <typedefs.h>
+#include <arch/cp15.h>
 #include <arch/stack.h>
 #include <config.h>
@@ -43 +44 @@
 #include <trace.h>
 
-/** No such instruction on ARM to sleep CPU. */
+/** CPU specific way to sleep cpu.
+ *
+ * ARMv7 introduced wait for event and wait for interrupt (wfe/wfi).
+ * ARM920T has custom coprocessor action to do the same. See ARM920T Technical
+ * Reference Manual ch 4.9 p. 4-23 (103 in the PDF)
+ * ARM926EJ-S uses the same coprocessor instruction as ARM920T. See ARM926EJ-S
+ * chapter 2.3.8 p.2-22 (52 in the PDF)
+ *
+ * @note Although CP15WFI (mcr p15, 0, R0, c7, c0, 4) is defined in ARM
+ * Architecture reference manual for armv4/5, CP15 implementation is mandatory
+ * only for armv6+.
+ */
 NO_TRACE static inline void cpu_sleep(void)
 {
+#ifdef PROCESSOR_ARCH_armv7_a
+        asm volatile ( "wfe" );
+#elif defined(PROCESSOR_ARCH_armv6) | defined(PROCESSOR_arm926ej_s) | defined(PROCESSOR_arm920t)
+        WFI_write(0);
+#endif
 }