From b460ac355757a182b75a7e8733372f47a3032fd1 Mon Sep 17 00:00:00 2001
From: patacongo <patacongo@42af7a65-404d-4744-a932-0658087f49c3>
Date: Mon, 18 May 2009 22:14:40 +0000
Subject: lm3s6918 now does context switches

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@1790 42af7a65-404d-4744-a932-0658087f49c3
---
 nuttx/arch/arm/src/common/up_initialstate.c | 32 +++++++++++++++++++++++++----
 nuttx/arch/arm/src/lm3s/lm3s_vectors.S      | 10 ++++-----
 2 files changed, 33 insertions(+), 9 deletions(-)

diff --git a/nuttx/arch/arm/src/common/up_initialstate.c b/nuttx/arch/arm/src/common/up_initialstate.c
index a945b4c51..9c683a950 100644
--- a/nuttx/arch/arm/src/common/up_initialstate.c
+++ b/nuttx/arch/arm/src/common/up_initialstate.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  *  arch/arm/src/common/up_initialstate.c
  *
- *   Copyright (C) 2007, 2008 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2009 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -40,10 +40,16 @@
 #include <nuttx/config.h>
 #include <sys/types.h>
 #include <string.h>
+
 #include <nuttx/arch.h>
+
 #include "up_internal.h"
 #include "up_arch.h"
 
+#ifdef __thumb2__
+#  include "cortexm3_psr.h"
+#endif
+
 /****************************************************************************
  * Private Definitions
  ****************************************************************************/
@@ -81,18 +87,36 @@ void up_initial_state(_TCB *tcb)
   /* Initialize the initial exception register context structure */
 
   memset(xcp, 0, sizeof(struct xcptcontext));
+
+  /* Save the initial stack point */
+
   xcp->regs[REG_SP]      = (uint32)tcb->adj_stack_ptr;
-  xcp->regs[REG_PC]      = (uint32)tcb->start;
 
 #ifdef __thumb2__
+  /* Save the task entry point (stripping off the thumb bit) */
+
+  xcp->regs[REG_PC]      = (uint32)tcb->start & ~1;
+  
+  /* Specify thumb mode */
+
+  xcp->regs[REG_XPSR]    = CORTEXM3_XPSR_T;
+
+  /* Enable or disable interrupts, based on user configuration */
+
 # ifdef CONFIG_SUPPRESS_INTERRUPTS
   xcp->regs[REG_PRIMASK] = 1;
 # endif
-#else
+#else /* __thumb2__ */
+  /* Save the task entry point */
+
+  xcp->regs[REG_PC]      = (uint32)tcb->start;
+
+  /* Enable or disable interrupts, based on user configuration */
+
 # ifdef CONFIG_SUPPRESS_INTERRUPTS
   xcp->regs[REG_CPSR]    = SVC_MODE | PSR_I_BIT | PSR_F_BIT;
 # else
   xcp->regs[REG_CPSR]    = SVC_MODE | PSR_F_BIT;
 # endif
-#endif
+#endif /* __thumb2__ */
 }
diff --git a/nuttx/arch/arm/src/lm3s/lm3s_vectors.S b/nuttx/arch/arm/src/lm3s/lm3s_vectors.S
index 5be36a90e..70774c464 100644
--- a/nuttx/arch/arm/src/lm3s/lm3s_vectors.S
+++ b/nuttx/arch/arm/src/lm3s/lm3s_vectors.S
@@ -298,7 +298,7 @@ lm3s_irqcommon:
 	 * as current stack pointer, then things are relatively easy.
 	 */
 
-	cmp	r0, r1
+	cmp	r0, r1			/* Context switch? */
 	beq	1f			/* Branch if no context switch */
 
 	/* We are returning with a pending context switch.  This case is different
@@ -307,11 +307,11 @@ lm3s_irqcommon:
 	 * values to the stack.
 	 */
 
-        add	r1, r0, #SW_XCPT_REGS	/* r2=offset HW save area */
-	ldmia	r1, {r4-r11}		/* Eight registers in HW save area */
+        add	r1, r0, #SW_XCPT_SIZE	/* R1=Address of HW save area in reg array */
+	ldmia	r1, {r4-r11}		/* Fetch eight registers in HW save area */
 	ldr	r1, [r0, #(4*REG_SP)]	/* R1=Value of SP before interrupt */
-	stmdb	r1!, {r4-r11}		/* Eight registers in HW save area */
-	ldmia	r0!, {r2-r11}		/* Recover R4-R11 + 2 temp values */
+	stmdb	r1!, {r4-r11}		/* Store eight registers in HW save area */
+	ldmia	r0, {r2-r11}		/* Recover R4-R11 + 2 temp values */
 	b	2f			/* Re-join common logic */
 
 	/* We are returning with no context switch.  We simply need to "unwind"
-- 
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