Improved certain Cortex-M3 context switch times

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@2177 42af7a65-404d-4744-a932-0658087f49c3

1 files changed, 95 insertions, 0 deletions

diff --git a/nuttx/arch/arm/src/cortexm3/up_switchcontext.S b/nuttx/arch/arm/src/cortexm3/up_switchcontext.S
new file mode 100755
index 000000000..055a7a268
--- /dev/null
+++ b/nuttx/arch/arm/src/cortexm3/up_switchcontext.S
@@ -0,0 +1,95 @@
+/************************************************************************************
+ * arch/arm/src/cortexm3/up_switchcontext.S
+ *
+ *   Copyright (C) 2009 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ************************************************************************************/
+
+/************************************************************************************
+ * Included Files
+ ************************************************************************************/
+
+#include <nuttx/config.h>
+#include <arch/irq.h>
+#include "nvic.h"
+
+/************************************************************************************
+ * Preprocessor Definitions
+ ************************************************************************************/
+
+/************************************************************************************
+ * Global Symbols
+ ************************************************************************************/
+
+	.syntax		unified
+	.thumb
+	.file		"up_context.S"
+
+/************************************************************************************
+ * Macros
+ ************************************************************************************/
+
+/************************************************************************************
+ * Public Functions
+ ************************************************************************************/
+
+/**************************************************************************
+ * Name: up_switchcontext
+ *
+ * Description:
+ *   Save the current thread context and restore the specified context.
+ *   Full prototype is:
+ *
+ *   void up_switchcontext(uint32 *saveregs, uint32 *restoreregs);
+ *
+ * Return:
+ *   None
+ *
+ **************************************************************************/
+
+	.thumb_func
+	.globl		up_switchcontext
+	.type		up_switchcontext, function
+up_switchcontext:
+
+	/* Perform the System call with R0=1, R1=saveregs, R2=restoreregs */
+
+	mov	r2, r1			/* R2: restoreregs */
+	mov	r1, r0			/* R1: saveregs */
+	mov	r0, #2			/* R0: 2 means context switch */
+	svc	0			/* Force synchronous SVCall (or Hard Fault) */
+
+	/* This call should not return */
+
+	bx	lr			/* Unnecessary ... will not return */
+	.size		up_switchcontext, .-up_switchcontext
+	.end
+