From 24469eee457801a9fe66f6dc77a74c05c50fdbaf Mon Sep 17 00:00:00 2001
From: gdisirio <gdisirio@35acf78f-673a-0410-8e92-d51de3d6d3f4>
Date: Wed, 13 Feb 2013 11:43:14 +0000
Subject: git-svn-id: svn://svn.code.sf.net/p/chibios/svn/trunk@5176
 35acf78f-673a-0410-8e92-d51de3d6d3f4

---
 os/ports/GCC/PPC/chcore.c | 14 +++++++++-----
 os/ports/GCC/PPC/chcore.h | 23 ++++++++++++++++++++++-
 2 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/os/ports/GCC/PPC/chcore.c b/os/ports/GCC/PPC/chcore.c
index 8403e0171..c3170c6cf 100644
--- a/os/ports/GCC/PPC/chcore.c
+++ b/os/ports/GCC/PPC/chcore.c
@@ -67,11 +67,11 @@ void port_halt(void) {
  * @param[in] ntp       the thread to be switched in
  * @param[in] otp       the thread to be switched out
  */
-void port_switch(Thread *ntp, Thread *otp) {
-
-  (void)otp;
-  (void)ntp;
+__attribute__((naked))
+void port_dummy1(void) {
 
+  asm (".global _port_switch");
+  asm ("_port_switch:");
   asm ("subi        %sp, %sp, 80");     /* Size of the intctx structure.    */
   asm ("mflr        %r0");
   asm ("stw         %r0, 84(%sp)");     /* LR into the caller frame.        */
@@ -88,6 +88,7 @@ void port_switch(Thread *ntp, Thread *otp) {
   asm ("lwz         %r0, 84(%sp)");     /* LR from the caller frame.        */
   asm ("mtlr        %r0");
   asm ("addi        %sp, %sp, 80");     /* Size of the intctx structure.    */
+  asm ("blr");
 }
 
 /**
@@ -95,8 +96,11 @@ void port_switch(Thread *ntp, Thread *otp) {
  * @details If the work function returns @p chThdExit() is automatically
  *          invoked.
  */
-void _port_thread_start(void) {
+__attribute__((naked))
+void port_dummy2(void) {
 
+  asm (".global _port_thread_start");
+  asm ("_port_thread_start:");
   chSysUnlock();
   asm ("mr          %r3, %r31");        /* Thread parameter.                */
   asm ("mtctr       %r30");
diff --git a/os/ports/GCC/PPC/chcore.h b/os/ports/GCC/PPC/chcore.h
index c64737c67..0f78b3b9b 100644
--- a/os/ports/GCC/PPC/chcore.h
+++ b/os/ports/GCC/PPC/chcore.h
@@ -341,6 +341,27 @@ struct context {
  */
 #define port_enable() asm volatile ("wrteei  1" : : : "memory")
 
+/**
+ * @brief   Performs a context switch between two threads.
+ * @details This is the most critical code in any port, this function
+ *          is responsible for the context switch between 2 threads.
+ * @note    The implementation of this code affects <b>directly</b> the context
+ *          switch performance so optimize here as much as you can.
+ *
+ * @param[in] ntp       the thread to be switched in
+ * @param[in] otp       the thread to be switched out
+ */
+#if !CH_DBG_ENABLE_STACK_CHECK || defined(__DOXYGEN__)
+#define port_switch(ntp, otp) _port_switch(ntp, otp)
+#else
+#define port_switch(ntp, otp) {                                             \
+  register struct intctx *sp asm ("%r1");                                   \
+  if ((stkalign_t *)(sp - 1) < otp->p_stklimit)                             \
+    chDbgPanic("stack overflow");                                           \
+  _port_switch(ntp, otp);                                                   \
+}
+#endif
+
 /**
  * @brief   Writes to a special register.
  *
@@ -369,7 +390,7 @@ extern "C" {
 #endif
   void port_init(void);
   void port_halt(void);
-  void port_switch(Thread *ntp, Thread *otp);
+  void _port_switch(Thread *ntp, Thread *otp);
   void _port_thread_start(void);
 #ifdef __cplusplus
 }
-- 
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