Add define for cpu idle.

git-svn-id: https://src.develer.com/svnoss/bertos/trunk@1047 38d2e660-2303-0410-9eaa-f027e97ec537

diff --git a/cpu/attr.h b/cpu/attr.h
index 678eac68287f010ea70002a962f8cc115a4fc9e1..497f899700d2712816480bd0792a53c4fd177dd9 100644 (file)
--- a/cpu/attr.h
+++ b/cpu/attr.h
@@ -256,6 +256,30 @@
                        CPU_PUSH_WORD((sp), funcaddr>>8); \
                } while (0)
 
+       /*
+        * If the kernel is in idle-spinning, the processor execute:
+        * 
+        * IRQ_ENABLE;
+        * CPU_IDLE;
+        * IRQ_DISABLE;
+        *
+        * IRQ_ENABLE is translated in asm as "sei" and IRQ_DISABLE as "cli".
+        * We could define CPU_IDLE to expand to none, so the resulting
+        * asm code would be:
+        *
+        * sei;
+        * cli;
+        *
+        * But Atmel datasheet states:
+        * "When using the SEI instruction to enable interrupts,
+        * the instruction following SEI will be executed *before*
+        * any pending interrupts", so "cli" is executed before any
+        * pending interrupt with the result that IRQs will *NOT*
+        * be enabled!
+        * To ensure that IRQ will run a NOP is required.
+        */
+       #define CPU_IDLE NOP
+
 #else
        #define CPU_PUSH_CALL_CONTEXT(sp, func) \
                CPU_PUSH_WORD((sp), (cpustack_t)(func))