git.sur5r.net Git - freertos/blob - FreeRTOS/Source/portable/GCC/ARM_CM0/port.c

   1 /*\r
   2     FreeRTOS V8.0.0 - Copyright (C) 2014 Real Time Engineers Ltd.\r
   3     All rights reserved\r
   4 \r
   5     VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.\r
   6 \r
   7     ***************************************************************************\r
   8      *                                                                       *\r
   9      *    FreeRTOS provides completely free yet professionally developed,    *\r
  10      *    robust, strictly quality controlled, supported, and cross          *\r
  11      *    platform software that has become a de facto standard.             *\r
  12      *                                                                       *\r
  13      *    Help yourself get started quickly and support the FreeRTOS         *\r
  14      *    project by purchasing a FreeRTOS tutorial book, reference          *\r
  15      *    manual, or both from: http://www.FreeRTOS.org/Documentation        *\r
  16      *                                                                       *\r
  17      *    Thank you!                                                         *\r
  18      *                                                                       *\r
  19     ***************************************************************************\r
  20 \r
  21     This file is part of the FreeRTOS distribution.\r
  22 \r
  23     FreeRTOS is free software; you can redistribute it and/or modify it under\r
  24     the terms of the GNU General Public License (version 2) as published by the\r
  25     Free Software Foundation >>!AND MODIFIED BY!<< the FreeRTOS exception.\r
  26 \r
  27     >>! NOTE: The modification to the GPL is included to allow you to distribute\r
  28     >>! a combined work that includes FreeRTOS without being obliged to provide\r
  29     >>! the source code for proprietary components outside of the FreeRTOS\r
  30     >>! kernel.\r
  31 \r
  32     FreeRTOS is distributed in the hope that it will be useful, but WITHOUT ANY\r
  33     WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS\r
  34     FOR A PARTICULAR PURPOSE.  Full license text is available from the following\r
  35     link: http://www.freertos.org/a00114.html\r
  36 \r
  37     1 tab == 4 spaces!\r
  38 \r
  39     ***************************************************************************\r
  40      *                                                                       *\r
  41      *    Having a problem?  Start by reading the FAQ "My application does   *\r
  42      *    not run, what could be wrong?"                                     *\r
  43      *                                                                       *\r
  44      *    http://www.FreeRTOS.org/FAQHelp.html                               *\r
  45      *                                                                       *\r
  46     ***************************************************************************\r
  47 \r
  48     http://www.FreeRTOS.org - Documentation, books, training, latest versions,\r
  49     license and Real Time Engineers Ltd. contact details.\r
  50 \r
  51     http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,\r
  52     including FreeRTOS+Trace - an indispensable productivity tool, a DOS\r
  53     compatible FAT file system, and our tiny thread aware UDP/IP stack.\r
  54 \r
  55     http://www.OpenRTOS.com - Real Time Engineers ltd license FreeRTOS to High\r
  56     Integrity Systems to sell under the OpenRTOS brand.  Low cost OpenRTOS\r
  57     licenses offer ticketed support, indemnification and middleware.\r
  58 \r
  59     http://www.SafeRTOS.com - High Integrity Systems also provide a safety\r
  60     engineered and independently SIL3 certified version for use in safety and\r
  61     mission critical applications that require provable dependability.\r
  62 \r
  63     1 tab == 4 spaces!\r
  64 */\r
  65 \r
  66 /*-----------------------------------------------------------\r
  67  * Implementation of functions defined in portable.h for the ARM CM0 port.\r
  68  *----------------------------------------------------------*/\r
  69 \r
  70 /* Scheduler includes. */\r
  71 #include "FreeRTOS.h"\r
  72 #include "task.h"\r
  73 \r
  74 /* Constants required to manipulate the NVIC. */\r
  75 #define portNVIC_SYSTICK_CTRL           ( ( volatile uint32_t *) 0xe000e010 )\r
  76 #define portNVIC_SYSTICK_LOAD           ( ( volatile uint32_t *) 0xe000e014 )\r
  77 #define portNVIC_INT_CTRL                       ( ( volatile uint32_t *) 0xe000ed04 )\r
  78 #define portNVIC_SYSPRI2                        ( ( volatile uint32_t *) 0xe000ed20 )\r
  79 #define portNVIC_SYSTICK_CLK            0x00000004\r
  80 #define portNVIC_SYSTICK_INT            0x00000002\r
  81 #define portNVIC_SYSTICK_ENABLE         0x00000001\r
  82 #define portNVIC_PENDSVSET                      0x10000000\r
  83 #define portMIN_INTERRUPT_PRIORITY      ( 255UL )\r
  84 #define portNVIC_PENDSV_PRI                     ( portMIN_INTERRUPT_PRIORITY << 16UL )\r
  85 #define portNVIC_SYSTICK_PRI            ( portMIN_INTERRUPT_PRIORITY << 24UL )\r
  86 \r
  87 /* Constants required to set up the initial stack. */\r
  88 #define portINITIAL_XPSR                        ( 0x01000000 )\r
  89 \r
  90 /* Let the user override the pre-loading of the initial LR with the address of\r
  91 prvTaskExitError() in case is messes up unwinding of the stack in the\r
  92 debugger. */\r
  93 #ifdef configTASK_RETURN_ADDRESS\r
  94         #define portTASK_RETURN_ADDRESS configTASK_RETURN_ADDRESS\r
  95 #else\r
  96         #define portTASK_RETURN_ADDRESS prvTaskExitError\r
  97 #endif\r
  98 \r
  99 /* Each task maintains its own interrupt status in the critical nesting\r
 100 variable. */\r
 101 static UBaseType_t uxCriticalNesting = 0xaaaaaaaa;\r
 102 \r
 103 /*\r
 104  * Setup the timer to generate the tick interrupts.\r
 105  */\r
 106 static void prvSetupTimerInterrupt( void );\r
 107 \r
 108 /*\r
 109  * Exception handlers.\r
 110  */\r
 111 void xPortPendSVHandler( void ) __attribute__ (( naked ));\r
 112 void xPortSysTickHandler( void );\r
 113 void vPortSVCHandler( void );\r
 114 \r
 115 /*\r
 116  * Start first task is a separate function so it can be tested in isolation.\r
 117  */\r
 118 static void vPortStartFirstTask( void ) __attribute__ (( naked ));\r
 119 \r
 120 /*\r
 121  * Used to catch tasks that attempt to return from their implementing function.\r
 122  */\r
 123 static void prvTaskExitError( void );\r
 124 \r
 125 /*-----------------------------------------------------------*/\r
 126 \r
 127 /*\r
 128  * See header file for description.\r
 129  */\r
 130 StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )\r
 131 {\r
 132         /* Simulate the stack frame as it would be created by a context switch\r
 133         interrupt. */\r
 134         pxTopOfStack--; /* Offset added to account for the way the MCU uses the stack on entry/exit of interrupts. */\r
 135         *pxTopOfStack = portINITIAL_XPSR;       /* xPSR */\r
 136         pxTopOfStack--;\r
 137         *pxTopOfStack = ( StackType_t ) pxCode; /* PC */\r
 138         pxTopOfStack--;\r
 139         *pxTopOfStack = ( StackType_t ) portTASK_RETURN_ADDRESS;        /* LR */\r
 140         pxTopOfStack -= 5;      /* R12, R3, R2 and R1. */\r
 141         *pxTopOfStack = ( StackType_t ) pvParameters;   /* R0 */\r
 142         pxTopOfStack -= 8; /* R11..R4. */\r
 143 \r
 144         return pxTopOfStack;\r
 145 }\r
 146 /*-----------------------------------------------------------*/\r
 147 \r
 148 static void prvTaskExitError( void )\r
 149 {\r
 150         /* A function that implements a task must not exit or attempt to return to\r
 151         its caller as there is nothing to return to.  If a task wants to exit it\r
 152         should instead call vTaskDelete( NULL ).\r
 153 \r
 154         Artificially force an assert() to be triggered if configASSERT() is\r
 155         defined, then stop here so application writers can catch the error. */\r
 156         configASSERT( uxCriticalNesting == ~0UL );\r
 157         portDISABLE_INTERRUPTS();\r
 158         for( ;; );\r
 159 }\r
 160 /*-----------------------------------------------------------*/\r
 161 \r
 162 void vPortSVCHandler( void )\r
 163 {\r
 164         /* This function is no longer used, but retained for backward\r
 165         compatibility. */\r
 166 }\r
 167 /*-----------------------------------------------------------*/\r
 168 \r
 169 void vPortStartFirstTask( void )\r
 170 {\r
 171         /* The MSP stack is not reset as, unlike on M3/4 parts, there is no vector\r
 172         table offset register that can be used to locate the initial stack value.\r
 173         Not all M0 parts have the application vector table at address 0. */\r
 174         __asm volatile(\r
 175         "       ldr     r2, pxCurrentTCBConst2  \n" /* Obtain location of pxCurrentTCB. */\r
 176         "       ldr r3, [r2]                            \n"\r
 177         "       ldr r0, [r3]                            \n" /* The first item in pxCurrentTCB is the task top of stack. */\r
 178         "       add r0, #32                                     \n" /* Discard everything up to r0. */\r
 179         "       msr psp, r0                                     \n" /* This is now the new top of stack to use in the task. */\r
 180         "       movs r0, #2                                     \n" /* Switch to the psp stack. */\r
 181         "       msr CONTROL, r0                         \n"\r
 182         "       pop {r0-r5}                                     \n" /* Pop the registers that are saved automatically. */\r
 183         "       mov lr, r5                                      \n" /* lr is now in r5. */\r
 184         "       cpsie i                                         \n" /* The first task has its context and interrupts can be enabled. */\r
 185         "       pop {pc}                                        \n" /* Finally, pop the PC to jump to the user defined task code. */\r
 186         "                                                               \n"\r
 187         "       .align 2                                        \n"\r
 188         "pxCurrentTCBConst2: .word pxCurrentTCB   "\r
 189                                   );\r
 190 }\r
 191 /*-----------------------------------------------------------*/\r
 192 \r
 193 /*\r
 194  * See header file for description.\r
 195  */\r
 196 BaseType_t xPortStartScheduler( void )\r
 197 {\r
 198         /* Make PendSV, CallSV and SysTick the same priroity as the kernel. */\r
 199         *(portNVIC_SYSPRI2) |= portNVIC_PENDSV_PRI;\r
 200         *(portNVIC_SYSPRI2) |= portNVIC_SYSTICK_PRI;\r
 201 \r
 202         /* Start the timer that generates the tick ISR.  Interrupts are disabled\r
 203         here already. */\r
 204         prvSetupTimerInterrupt();\r
 205 \r
 206         /* Initialise the critical nesting count ready for the first task. */\r
 207         uxCriticalNesting = 0;\r
 208 \r
 209         /* Start the first task. */\r
 210         vPortStartFirstTask();\r
 211 \r
 212         /* Should never get here as the tasks will now be executing!  Call the task\r
 213         exit error function to prevent compiler warnings about a static function\r
 214         not being called in the case that the application writer overrides this\r
 215         functionality by defining configTASK_RETURN_ADDRESS. */\r
 216         prvTaskExitError();\r
 217 \r
 218         /* Should not get here! */\r
 219         return 0;\r
 220 }\r
 221 /*-----------------------------------------------------------*/\r
 222 \r
 223 void vPortEndScheduler( void )\r
 224 {\r
 225         /* Not implemented in ports where there is nothing to return to.\r
 226         Artificially force an assert. */\r
 227         configASSERT( uxCriticalNesting == 1000UL );\r
 228 }\r
 229 /*-----------------------------------------------------------*/\r
 230 \r
 231 void vPortYield( void )\r
 232 {\r
 233         /* Set a PendSV to request a context switch. */\r
 234         *( portNVIC_INT_CTRL ) = portNVIC_PENDSVSET;\r
 235 \r
 236         /* Barriers are normally not required but do ensure the code is completely\r
 237         within the specified behaviour for the architecture. */\r
 238         __asm volatile( "dsb" );\r
 239         __asm volatile( "isb" );\r
 240 }\r
 241 /*-----------------------------------------------------------*/\r
 242 \r
 243 void vPortEnterCritical( void )\r
 244 {\r
 245     portDISABLE_INTERRUPTS();\r
 246     uxCriticalNesting++;\r
 247         __asm volatile( "dsb" );\r
 248         __asm volatile( "isb" );\r
 249 }\r
 250 /*-----------------------------------------------------------*/\r
 251 \r
 252 void vPortExitCritical( void )\r
 253 {\r
 254         configASSERT( uxCriticalNesting );\r
 255     uxCriticalNesting--;\r
 256     if( uxCriticalNesting == 0 )\r
 257     {\r
 258         portENABLE_INTERRUPTS();\r
 259     }\r
 260 }\r
 261 /*-----------------------------------------------------------*/\r
 262 \r
 263 uint32_t ulSetInterruptMaskFromISR( void )\r
 264 {\r
 265         __asm volatile(\r
 266                                         " mrs r0, PRIMASK       \n"\r
 267                                         " cpsid i                       \n"\r
 268                                         " bx lr                           "\r
 269                                   );\r
 270 \r
 271         /* To avoid compiler warnings.  This line will never be reached. */\r
 272         return 0;\r
 273 }\r
 274 /*-----------------------------------------------------------*/\r
 275 \r
 276 void vClearInterruptMaskFromISR( uint32_t ulMask )\r
 277 {\r
 278         __asm volatile(\r
 279                                         " msr PRIMASK, r0       \n"\r
 280                                         " bx lr                           "\r
 281                                   );\r
 282 \r
 283         /* Just to avoid compiler warning. */\r
 284         ( void ) ulMask;\r
 285 }\r
 286 /*-----------------------------------------------------------*/\r
 287 \r
 288 void xPortPendSVHandler( void )\r
 289 {\r
 290         /* This is a naked function. */\r
 291 \r
 292         __asm volatile\r
 293         (\r
 294         "       mrs r0, psp                                                     \n"\r
 295         "                                                                               \n"\r
 296         "       ldr     r3, pxCurrentTCBConst                   \n" /* Get the location of the current TCB. */\r
 297         "       ldr     r2, [r3]                                                \n"\r
 298         "                                                                               \n"\r
 299         "       sub r0, r0, #32                                         \n" /* Make space for the remaining low registers. */\r
 300         "       str r0, [r2]                                            \n" /* Save the new top of stack. */\r
 301         "       stmia r0!, {r4-r7}                                      \n" /* Store the low registers that are not saved automatically. */\r
 302         "       mov r4, r8                                                      \n" /* Store the high registers. */\r
 303         "       mov r5, r9                                                      \n"\r
 304         "       mov r6, r10                                                     \n"\r
 305         "       mov r7, r11                                                     \n"\r
 306         "       stmia r0!, {r4-r7}                      \n"\r
 307         "                                                                               \n"\r
 308         "       push {r3, r14}                                          \n"\r
 309         "       cpsid i                                                         \n"\r
 310         "       bl vTaskSwitchContext                           \n"\r
 311         "       cpsie i                                                         \n"\r
 312         "       pop {r2, r3}                                            \n" /* lr goes in r3. r2 now holds tcb pointer. */\r
 313         "                                                                               \n"\r
 314         "       ldr r1, [r2]                                            \n"\r
 315         "       ldr r0, [r1]                                            \n" /* The first item in pxCurrentTCB is the task top of stack. */\r
 316         "       add r0, r0, #16                                         \n" /* Move to the high registers. */\r
 317         "       ldmia r0!, {r4-r7}                                      \n" /* Pop the high registers. */\r
 318         "       mov r8, r4                                                      \n"\r
 319         "       mov r9, r5                                                      \n"\r
 320         "       mov r10, r6                                                     \n"\r
 321         "       mov r11, r7                                                     \n"\r
 322         "                                                                               \n"\r
 323         "       msr psp, r0                                                     \n" /* Remember the new top of stack for the task. */\r
 324         "                                                                               \n"\r
 325         "       sub r0, r0, #32                                         \n" /* Go back for the low registers that are not automatically restored. */\r
 326         "       ldmia r0!, {r4-r7}                      \n" /* Pop low registers.  */\r
 327         "                                                                               \n"\r
 328         "       bx r3                                                           \n"\r
 329         "                                                                               \n"\r
 330         "       .align 2                                                        \n"\r
 331         "pxCurrentTCBConst: .word pxCurrentTCB    "\r
 332         );\r
 333 }\r
 334 /*-----------------------------------------------------------*/\r
 335 \r
 336 void xPortSysTickHandler( void )\r
 337 {\r
 338 uint32_t ulPreviousMask;\r
 339 \r
 340         ulPreviousMask = portSET_INTERRUPT_MASK_FROM_ISR();\r
 341         {\r
 342                 /* Increment the RTOS tick. */\r
 343                 if( xTaskIncrementTick() != pdFALSE )\r
 344                 {\r
 345                         /* Pend a context switch. */\r
 346                         *(portNVIC_INT_CTRL) = portNVIC_PENDSVSET;\r
 347                 }\r
 348         }\r
 349         portCLEAR_INTERRUPT_MASK_FROM_ISR( ulPreviousMask );\r
 350 }\r
 351 /*-----------------------------------------------------------*/\r
 352 \r
 353 /*\r
 354  * Setup the systick timer to generate the tick interrupts at the required\r
 355  * frequency.\r
 356  */\r
 357 void prvSetupTimerInterrupt( void )\r
 358 {\r
 359         /* Configure SysTick to interrupt at the requested rate. */\r
 360         *(portNVIC_SYSTICK_LOAD) = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;\r
 361         *(portNVIC_SYSTICK_CTRL) = portNVIC_SYSTICK_CLK | portNVIC_SYSTICK_INT | portNVIC_SYSTICK_ENABLE;\r
 362 }\r
 363 /*-----------------------------------------------------------*/\r
 364 \r