FreeRTOS/Source/portable/GCC/ARM7_LPC2000/port.c

   1 /*
   2     FreeRTOS V6.0.5 - Copyright (C) 2010 Real Time Engineers Ltd.
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  25     This file is part of the FreeRTOS distribution.
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  52 */
  53
  54
  55 /*-----------------------------------------------------------
  56  * Implementation of functions defined in portable.h for the ARM7 port.
  57  *
  58  * Components that can be compiled to either ARM or THUMB mode are
  59  * contained in this file.  The ISR routines, which can only be compiled
  60  * to ARM mode are contained in portISR.c.
  61  *----------------------------------------------------------*/
  62
  63
  64 /* Standard includes. */
  65 #include <stdlib.h>
  66
  67 /* Scheduler includes. */
  68 #include "FreeRTOS.h"
  69 #include "task.h"
  70
  71 /* Constants required to setup the task context. */
  72 #define portINITIAL_SPSR                                ( ( portSTACK_TYPE ) 0x1f ) /* System mode, ARM mode, interrupts enabled. */
  73 #define portTHUMB_MODE_BIT                              ( ( portSTACK_TYPE ) 0x20 )
  74 #define portINSTRUCTION_SIZE                    ( ( portSTACK_TYPE ) 4 )
  75 #define portNO_CRITICAL_SECTION_NESTING ( ( portSTACK_TYPE ) 0 )
  76
  77 /* Constants required to setup the tick ISR. */
  78 #define portENABLE_TIMER                        ( ( unsigned char ) 0x01 )
  79 #define portPRESCALE_VALUE                      0x00
  80 #define portINTERRUPT_ON_MATCH          ( ( unsigned long ) 0x01 )
  81 #define portRESET_COUNT_ON_MATCH        ( ( unsigned long ) 0x02 )
  82
  83 /* Constants required to setup the VIC for the tick ISR. */
  84 #define portTIMER_VIC_CHANNEL           ( ( unsigned long ) 0x0004 )
  85 #define portTIMER_VIC_CHANNEL_BIT       ( ( unsigned long ) 0x0010 )
  86 #define portTIMER_VIC_ENABLE            ( ( unsigned long ) 0x0020 )
  87
  88 /*-----------------------------------------------------------*/
  89
  90 /* Setup the timer to generate the tick interrupts. */
  91 static void prvSetupTimerInterrupt( void );
  92
  93 /*
  94  * The scheduler can only be started from ARM mode, so
  95  * vPortISRStartFirstSTask() is defined in portISR.c.
  96  */
  97 extern void vPortISRStartFirstTask( void );
  98
  99 /*-----------------------------------------------------------*/
 100
 101 /*
 102  * Initialise the stack of a task to look exactly as if a call to
 103  * portSAVE_CONTEXT had been called.
 104  *
 105  * See header file for description.
 106  */
 107 portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
 108 {
 109 portSTACK_TYPE *pxOriginalTOS;
 110
 111         pxOriginalTOS = pxTopOfStack;
 112
 113         /* Setup the initial stack of the task.  The stack is set exactly as
 114         expected by the portRESTORE_CONTEXT() macro. */
 115
 116         /* First on the stack is the return address - which in this case is the
 117         start of the task.  The offset is added to make the return address appear
 118         as it would within an IRQ ISR. */
 119         *pxTopOfStack = ( portSTACK_TYPE ) pxCode + portINSTRUCTION_SIZE;
 120         pxTopOfStack--;
 121
 122         *pxTopOfStack = ( portSTACK_TYPE ) 0xaaaaaaaa;  /* R14 */
 123         pxTopOfStack--;
 124         *pxTopOfStack = ( portSTACK_TYPE ) pxOriginalTOS; /* Stack used when task starts goes in R13. */
 125         pxTopOfStack--;
 126         *pxTopOfStack = ( portSTACK_TYPE ) 0x12121212;  /* R12 */
 127         pxTopOfStack--;
 128         *pxTopOfStack = ( portSTACK_TYPE ) 0x11111111;  /* R11 */
 129         pxTopOfStack--;
 130         *pxTopOfStack = ( portSTACK_TYPE ) 0x10101010;  /* R10 */
 131         pxTopOfStack--;
 132         *pxTopOfStack = ( portSTACK_TYPE ) 0x09090909;  /* R9 */
 133         pxTopOfStack--;
 134         *pxTopOfStack = ( portSTACK_TYPE ) 0x08080808;  /* R8 */
 135         pxTopOfStack--;
 136         *pxTopOfStack = ( portSTACK_TYPE ) 0x07070707;  /* R7 */
 137         pxTopOfStack--;
 138         *pxTopOfStack = ( portSTACK_TYPE ) 0x06060606;  /* R6 */
 139         pxTopOfStack--;
 140         *pxTopOfStack = ( portSTACK_TYPE ) 0x05050505;  /* R5 */
 141         pxTopOfStack--;
 142         *pxTopOfStack = ( portSTACK_TYPE ) 0x04040404;  /* R4 */
 143         pxTopOfStack--;
 144         *pxTopOfStack = ( portSTACK_TYPE ) 0x03030303;  /* R3 */
 145         pxTopOfStack--;
 146         *pxTopOfStack = ( portSTACK_TYPE ) 0x02020202;  /* R2 */
 147         pxTopOfStack--;
 148         *pxTopOfStack = ( portSTACK_TYPE ) 0x01010101;  /* R1 */
 149         pxTopOfStack--;
 150
 151         /* When the task starts is will expect to find the function parameter in
 152         R0. */
 153         *pxTopOfStack = ( portSTACK_TYPE ) pvParameters; /* R0 */
 154         pxTopOfStack--;
 155
 156         /* The last thing onto the stack is the status register, which is set for
 157         system mode, with interrupts enabled. */
 158         *pxTopOfStack = ( portSTACK_TYPE ) portINITIAL_SPSR;
 159
 160         if( ( ( unsigned long ) pxCode & 0x01UL ) != 0x00 )
 161         {
 162                 /* We want the task to start in thumb mode. */
 163                 *pxTopOfStack |= portTHUMB_MODE_BIT;
 164         }
 165
 166         pxTopOfStack--;
 167
 168         /* Some optimisation levels use the stack differently to others.  This
 169         means the interrupt flags cannot always be stored on the stack and will
 170         instead be stored in a variable, which is then saved as part of the
 171         tasks context. */
 172         *pxTopOfStack = portNO_CRITICAL_SECTION_NESTING;
 173
 174         return pxTopOfStack;
 175 }
 176 /*-----------------------------------------------------------*/
 177
 178 portBASE_TYPE xPortStartScheduler( void )
 179 {
 180         /* Start the timer that generates the tick ISR.  Interrupts are disabled
 181         here already. */
 182         prvSetupTimerInterrupt();
 183
 184         /* Start the first task. */
 185         vPortISRStartFirstTask();
 186
 187         /* Should not get here! */
 188         return 0;
 189 }
 190 /*-----------------------------------------------------------*/
 191
 192 void vPortEndScheduler( void )
 193 {
 194         /* It is unlikely that the ARM port will require this function as there
 195         is nothing to return to.  */
 196 }
 197 /*-----------------------------------------------------------*/
 198
 199 /*
 200  * Setup the timer 0 to generate the tick interrupts at the required frequency.
 201  */
 202 static void prvSetupTimerInterrupt( void )
 203 {
 204 unsigned long ulCompareMatch;
 205 extern void ( vTickISR )( void );
 206
 207         /* A 1ms tick does not require the use of the timer prescale.  This is
 208         defaulted to zero but can be used if necessary. */
 209         T0_PR = portPRESCALE_VALUE;
 210
 211         /* Calculate the match value required for our wanted tick rate. */
 212         ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;
 213
 214         /* Protect against divide by zero.  Using an if() statement still results
 215         in a warning - hence the #if. */
 216         #if portPRESCALE_VALUE != 0
 217         {
 218                 ulCompareMatch /= ( portPRESCALE_VALUE + 1 );
 219         }
 220         #endif
 221         T0_MR0 = ulCompareMatch;
 222
 223         /* Generate tick with timer 0 compare match. */
 224         T0_MCR = portRESET_COUNT_ON_MATCH | portINTERRUPT_ON_MATCH;
 225
 226         /* Setup the VIC for the timer. */
 227         VICIntSelect &= ~( portTIMER_VIC_CHANNEL_BIT );
 228         VICIntEnable |= portTIMER_VIC_CHANNEL_BIT;
 229
 230         /* The ISR installed depends on whether the preemptive or cooperative
 231         scheduler is being used. */
 232
 233         VICVectAddr0 = ( long ) vTickISR;
 234         VICVectCntl0 = portTIMER_VIC_CHANNEL | portTIMER_VIC_ENABLE;
 235
 236         /* Start the timer - interrupts are disabled when this function is called
 237         so it is okay to do this here. */
 238         T0_TCR = portENABLE_TIMER;
 239 }
 240 /*-----------------------------------------------------------*/
 241
 242
 243