git.sur5r.net Git - freertos/blob - Source/portable/GCC/ARM_CM3/port.c

   1 /*\r
   2         FreeRTOS V5.4.1 - Copyright (C) 2009 Real Time Engineers Ltd.\r
   3 \r
   4         This file is part of the FreeRTOS distribution.\r
   5 \r
   6         FreeRTOS is free software; you can redistribute it and/or modify it     under \r
   7         the terms of the GNU General Public License (version 2) as published by the \r
   8         Free Software Foundation and modified by the FreeRTOS exception.\r
   9         **NOTE** The exception to the GPL is included to allow you to distribute a\r
  10         combined work that includes FreeRTOS without being obliged to provide the \r
  11         source code for proprietary components outside of the FreeRTOS kernel.  \r
  12         Alternative commercial license and support terms are also available upon \r
  13         request.  See the licensing section of http://www.FreeRTOS.org for full \r
  14         license details.\r
  15 \r
  16         FreeRTOS is distributed in the hope that it will be useful,     but WITHOUT\r
  17         ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or\r
  18         FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for\r
  19         more details.\r
  20 \r
  21         You should have received a copy of the GNU General Public License along\r
  22         with FreeRTOS; if not, write to the Free Software Foundation, Inc., 59\r
  23         Temple Place, Suite 330, Boston, MA  02111-1307  USA.\r
  24 \r
  25 \r
  26         ***************************************************************************\r
  27         *                                                                         *\r
  28         * Looking for a quick start?  Then check out the FreeRTOS eBook!          *\r
  29         * See http://www.FreeRTOS.org/Documentation for details                   *\r
  30         *                                                                         *\r
  31         ***************************************************************************\r
  32 \r
  33         1 tab == 4 spaces!\r
  34 \r
  35         Please ensure to read the configuration and relevant port sections of the\r
  36         online documentation.\r
  37 \r
  38         http://www.FreeRTOS.org - Documentation, latest information, license and\r
  39         contact details.\r
  40 \r
  41         http://www.SafeRTOS.com - A version that is certified for use in safety\r
  42         critical systems.\r
  43 \r
  44         http://www.OpenRTOS.com - Commercial support, development, porting,\r
  45         licensing and training services.\r
  46 */\r
  47 \r
  48 /*-----------------------------------------------------------\r
  49  * Implementation of functions defined in portable.h for the ARM CM3 port.\r
  50  *----------------------------------------------------------*/\r
  51 \r
  52 /* Scheduler includes. */\r
  53 #include "FreeRTOS.h"\r
  54 #include "task.h"\r
  55 \r
  56 /* For backward compatibility, ensure configKERNEL_INTERRUPT_PRIORITY is\r
  57 defined.  The value should also ensure backward compatibility.\r
  58 FreeRTOS.org versions prior to V4.4.0 did not include this definition. */\r
  59 #ifndef configKERNEL_INTERRUPT_PRIORITY\r
  60         #define configKERNEL_INTERRUPT_PRIORITY 255\r
  61 #endif\r
  62 \r
  63 /* Constants required to manipulate the NVIC. */\r
  64 #define portNVIC_SYSTICK_CTRL           ( ( volatile unsigned portLONG *) 0xe000e010 )\r
  65 #define portNVIC_SYSTICK_LOAD           ( ( volatile unsigned portLONG *) 0xe000e014 )\r
  66 #define portNVIC_INT_CTRL                       ( ( volatile unsigned portLONG *) 0xe000ed04 )\r
  67 #define portNVIC_SYSPRI2                        ( ( volatile unsigned portLONG *) 0xe000ed20 )\r
  68 #define portNVIC_SYSTICK_CLK            0x00000004\r
  69 #define portNVIC_SYSTICK_INT            0x00000002\r
  70 #define portNVIC_SYSTICK_ENABLE         0x00000001\r
  71 #define portNVIC_PENDSVSET                      0x10000000\r
  72 #define portNVIC_PENDSV_PRI                     ( ( ( unsigned portLONG ) configKERNEL_INTERRUPT_PRIORITY ) << 16 )\r
  73 #define portNVIC_SYSTICK_PRI            ( ( ( unsigned portLONG ) configKERNEL_INTERRUPT_PRIORITY ) << 24 )\r
  74 \r
  75 /* Constants required to set up the initial stack. */\r
  76 #define portINITIAL_XPSR                        ( 0x01000000 )\r
  77 \r
  78 /* The priority used by the kernel is assigned to a variable to make access\r
  79 from inline assembler easier. */\r
  80 const unsigned portLONG ulKernelPriority = configKERNEL_INTERRUPT_PRIORITY;\r
  81 \r
  82 /* Each task maintains its own interrupt status in the critical nesting\r
  83 variable. */\r
  84 static unsigned portBASE_TYPE uxCriticalNesting = 0xaaaaaaaa;\r
  85 \r
  86 /*\r
  87  * Setup the timer to generate the tick interrupts.\r
  88  */\r
  89 static void prvSetupTimerInterrupt( void );\r
  90 \r
  91 /*\r
  92  * Exception handlers.\r
  93  */\r
  94 void xPortPendSVHandler( void ) __attribute__ (( naked ));\r
  95 void xPortSysTickHandler( void );\r
  96 void vPortSVCHandler( void ) __attribute__ (( naked ));\r
  97 \r
  98 /*\r
  99  * Start first task is a separate function so it can be tested in isolation.\r
 100  */\r
 101 void vPortStartFirstTask( void ) __attribute__ (( naked ));\r
 102 \r
 103 /*-----------------------------------------------------------*/\r
 104 \r
 105 /*\r
 106  * See header file for description.\r
 107  */\r
 108 portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )\r
 109 {\r
 110         /* Simulate the stack frame as it would be created by a context switch\r
 111         interrupt. */\r
 112         *pxTopOfStack = portINITIAL_XPSR;       /* xPSR */\r
 113         pxTopOfStack--;\r
 114         *pxTopOfStack = ( portSTACK_TYPE ) pxCode;      /* PC */\r
 115         pxTopOfStack--;\r
 116         *pxTopOfStack = 0;      /* LR */\r
 117         pxTopOfStack -= 5;      /* R12, R3, R2 and R1. */\r
 118         *pxTopOfStack = ( portSTACK_TYPE ) pvParameters;        /* R0 */\r
 119         pxTopOfStack -= 8;      /* R11, R10, R9, R8, R7, R6, R5 and R4. */\r
 120 \r
 121         return pxTopOfStack;\r
 122 }\r
 123 /*-----------------------------------------------------------*/\r
 124 \r
 125 void vPortSVCHandler( void )\r
 126 {\r
 127         __asm volatile (\r
 128                                         "       ldr     r3, pxCurrentTCBConst2          \n" /* Restore the context. */\r
 129                                         "       ldr r1, [r3]                                    \n" /* Use pxCurrentTCBConst to get the pxCurrentTCB address. */\r
 130                                         "       ldr r0, [r1]                                    \n" /* The first item in pxCurrentTCB is the task top of stack. */\r
 131                                         "       ldmia r0!, {r4-r11}                             \n" /* Pop the registers that are not automatically saved on exception entry and the critical nesting count. */\r
 132                                         "       msr psp, r0                                             \n" /* Restore the task stack pointer. */\r
 133                                         "       mov r0, #0                                              \n"\r
 134                                         "       msr     basepri, r0                                     \n"\r
 135                                         "       orr r14, #0xd                                   \n"\r
 136                                         "       bx r14                                                  \n"\r
 137                                         "                                                                       \n"\r
 138                                         "       .align 2                                                \n"\r
 139                                         "pxCurrentTCBConst2: .word pxCurrentTCB                         \n"\r
 140                                 );\r
 141 }\r
 142 /*-----------------------------------------------------------*/\r
 143 \r
 144 void vPortStartFirstTask( void )\r
 145 {\r
 146         __asm volatile(\r
 147                                         " ldr r0, =0xE000ED08   \n" /* Use the NVIC offset register to locate the stack. */\r
 148                                         " ldr r0, [r0]                  \n"\r
 149                                         " ldr r0, [r0]                  \n"\r
 150                                         " msr msp, r0                   \n" /* Set the msp back to the start of the stack. */\r
 151                                         " svc 0                                 \n" /* System call to start first task. */\r
 152                                 );\r
 153 }\r
 154 /*-----------------------------------------------------------*/\r
 155 \r
 156 /*\r
 157  * See header file for description.\r
 158  */\r
 159 portBASE_TYPE xPortStartScheduler( void )\r
 160 {\r
 161         /* Make PendSV, CallSV and SysTick the same priroity as the kernel. */\r
 162         *(portNVIC_SYSPRI2) |= portNVIC_PENDSV_PRI;\r
 163         *(portNVIC_SYSPRI2) |= portNVIC_SYSTICK_PRI;\r
 164 \r
 165         /* Start the timer that generates the tick ISR.  Interrupts are disabled\r
 166         here already. */\r
 167         prvSetupTimerInterrupt();\r
 168 \r
 169         /* Initialise the critical nesting count ready for the first task. */\r
 170         uxCriticalNesting = 0;\r
 171 \r
 172         /* Start the first task. */\r
 173         vPortStartFirstTask();\r
 174 \r
 175         /* Should not get here! */\r
 176         return 0;\r
 177 }\r
 178 /*-----------------------------------------------------------*/\r
 179 \r
 180 void vPortEndScheduler( void )\r
 181 {\r
 182         /* It is unlikely that the CM3 port will require this function as there\r
 183         is nothing to return to.  */\r
 184 }\r
 185 /*-----------------------------------------------------------*/\r
 186 \r
 187 void vPortYieldFromISR( void )\r
 188 {\r
 189         /* Set a PendSV to request a context switch. */\r
 190         *(portNVIC_INT_CTRL) = portNVIC_PENDSVSET;\r
 191 }\r
 192 /*-----------------------------------------------------------*/\r
 193 \r
 194 void vPortEnterCritical( void )\r
 195 {\r
 196         portDISABLE_INTERRUPTS();\r
 197         uxCriticalNesting++;\r
 198 }\r
 199 /*-----------------------------------------------------------*/\r
 200 \r
 201 void vPortExitCritical( void )\r
 202 {\r
 203         uxCriticalNesting--;\r
 204         if( uxCriticalNesting == 0 )\r
 205         {\r
 206                 portENABLE_INTERRUPTS();\r
 207         }\r
 208 }\r
 209 /*-----------------------------------------------------------*/\r
 210 \r
 211 void xPortPendSVHandler( void )\r
 212 {\r
 213         /* This is a naked function. */\r
 214 \r
 215         __asm volatile\r
 216         (\r
 217         "       mrs r0, psp                                                     \n"\r
 218         "                                                                               \n"\r
 219         "       ldr     r3, pxCurrentTCBConst                   \n" /* Get the location of the current TCB. */\r
 220         "       ldr     r2, [r3]                                                \n"\r
 221         "                                                                               \n"\r
 222         "       stmdb r0!, {r4-r11}                                     \n" /* Save the remaining registers. */\r
 223         "       str r0, [r2]                                            \n" /* Save the new top of stack into the first member of the TCB. */\r
 224         "                                                                               \n"\r
 225         "       stmdb sp!, {r3, r14}                            \n"\r
 226         "       mov r0, %0                                                      \n"\r
 227         "       msr basepri, r0                                         \n"\r
 228         "       bl vTaskSwitchContext                           \n"\r
 229         "       mov r0, #0                                                      \n"\r
 230         "       msr basepri, r0                                         \n"\r
 231         "       ldmia sp!, {r3, r14}                            \n"\r
 232         "                                                                               \n"     /* Restore the context, including the critical nesting count. */\r
 233         "       ldr r1, [r3]                                            \n"\r
 234         "       ldr r0, [r1]                                            \n" /* The first item in pxCurrentTCB is the task top of stack. */\r
 235         "       ldmia r0!, {r4-r11}                                     \n" /* Pop the registers. */\r
 236         "       msr psp, r0                                                     \n"\r
 237         "       bx r14                                                          \n"\r
 238         "                                                                               \n"\r
 239         "       .align 2                                                        \n"\r
 240         "pxCurrentTCBConst: .word pxCurrentTCB  \n"\r
 241         ::"i"(configMAX_SYSCALL_INTERRUPT_PRIORITY)\r
 242         );\r
 243 }\r
 244 /*-----------------------------------------------------------*/\r
 245 \r
 246 void xPortSysTickHandler( void )\r
 247 {\r
 248 unsigned portLONG ulDummy;\r
 249 \r
 250         /* If using preemption, also force a context switch. */\r
 251         #if configUSE_PREEMPTION == 1\r
 252                 *(portNVIC_INT_CTRL) = portNVIC_PENDSVSET;\r
 253         #endif\r
 254 \r
 255         ulDummy = portSET_INTERRUPT_MASK_FROM_ISR();\r
 256         {\r
 257                 vTaskIncrementTick();\r
 258         }\r
 259         portCLEAR_INTERRUPT_MASK_FROM_ISR( ulDummy );\r
 260 }\r
 261 /*-----------------------------------------------------------*/\r
 262 \r
 263 /*\r
 264  * Setup the systick timer to generate the tick interrupts at the required\r
 265  * frequency.\r
 266  */\r
 267 void prvSetupTimerInterrupt( void )\r
 268 {\r
 269         /* Configure SysTick to interrupt at the requested rate. */\r
 270         *(portNVIC_SYSTICK_LOAD) = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;\r
 271         *(portNVIC_SYSTICK_CTRL) = portNVIC_SYSTICK_CLK | portNVIC_SYSTICK_INT | portNVIC_SYSTICK_ENABLE;\r
 272 }\r
 273 /*-----------------------------------------------------------*/\r
 274 \r