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

   1 /*\r
   2     FreeRTOS V6.0.0 - 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     * The FreeRTOS eBook and reference manual are available to purchase for a *\r
  29     * small fee. Help yourself get started quickly while also helping the     *\r
  30     * FreeRTOS project! See http://www.FreeRTOS.org/Documentation for details *\r
  31     *                                                                         *\r
  32     ***************************************************************************\r
  33 \r
  34     1 tab == 4 spaces!\r
  35 \r
  36     Please ensure to read the configuration and relevant port sections of the\r
  37     online documentation.\r
  38 \r
  39     http://www.FreeRTOS.org - Documentation, latest information, license and\r
  40     contact details.\r
  41 \r
  42     http://www.SafeRTOS.com - A version that is certified for use in safety\r
  43     critical systems.\r
  44 \r
  45     http://www.OpenRTOS.com - Commercial support, development, porting,\r
  46     licensing and training services.\r
  47 */\r
  48 \r
  49 /*-----------------------------------------------------------\r
  50  * Implementation of functions defined in portable.h for the ARM CM3 port.\r
  51  *----------------------------------------------------------*/\r
  52 \r
  53 /* Scheduler includes. */\r
  54 #include "FreeRTOS.h"\r
  55 #include "task.h"\r
  56 \r
  57 /* For backward compatibility, ensure configKERNEL_INTERRUPT_PRIORITY is\r
  58 defined.  The value should also ensure backward compatibility.\r
  59 FreeRTOS.org versions prior to V4.4.0 did not include this definition. */\r
  60 #ifndef configKERNEL_INTERRUPT_PRIORITY\r
  61         #define configKERNEL_INTERRUPT_PRIORITY 255\r
  62 #endif\r
  63 \r
  64 /* Constants required to manipulate the NVIC. */\r
  65 #define portNVIC_SYSTICK_CTRL           ( ( volatile unsigned long *) 0xe000e010 )\r
  66 #define portNVIC_SYSTICK_LOAD           ( ( volatile unsigned long *) 0xe000e014 )\r
  67 #define portNVIC_INT_CTRL                       ( ( volatile unsigned long *) 0xe000ed04 )\r
  68 #define portNVIC_SYSPRI2                        ( ( volatile unsigned long *) 0xe000ed20 )\r
  69 #define portNVIC_SYSTICK_CLK            0x00000004\r
  70 #define portNVIC_SYSTICK_INT            0x00000002\r
  71 #define portNVIC_SYSTICK_ENABLE         0x00000001\r
  72 #define portNVIC_PENDSVSET                      0x10000000\r
  73 #define portNVIC_PENDSV_PRI                     ( ( ( unsigned long ) configKERNEL_INTERRUPT_PRIORITY ) << 16 )\r
  74 #define portNVIC_SYSTICK_PRI            ( ( ( unsigned long ) configKERNEL_INTERRUPT_PRIORITY ) << 24 )\r
  75 \r
  76 /* Constants required to set up the initial stack. */\r
  77 #define portINITIAL_XPSR                        ( 0x01000000 )\r
  78 \r
  79 /* The priority used by the kernel is assigned to a variable to make access\r
  80 from inline assembler easier. */\r
  81 const unsigned long ulKernelPriority = configKERNEL_INTERRUPT_PRIORITY;\r
  82 \r
  83 /* Each task maintains its own interrupt status in the critical nesting\r
  84 variable. */\r
  85 static unsigned portBASE_TYPE uxCriticalNesting = 0xaaaaaaaa;\r
  86 \r
  87 /*\r
  88  * Setup the timer to generate the tick interrupts.\r
  89  */\r
  90 static void prvSetupTimerInterrupt( void );\r
  91 \r
  92 /*\r
  93  * Exception handlers.\r
  94  */\r
  95 void xPortPendSVHandler( void ) __attribute__ (( naked ));\r
  96 void xPortSysTickHandler( void );\r
  97 void vPortSVCHandler( void ) __attribute__ (( naked ));\r
  98 \r
  99 /*\r
 100  * Start first task is a separate function so it can be tested in isolation.\r
 101  */\r
 102 void vPortStartFirstTask( void ) __attribute__ (( naked ));\r
 103 \r
 104 /*-----------------------------------------------------------*/\r
 105 \r
 106 /*\r
 107  * See header file for description.\r
 108  */\r
 109 portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )\r
 110 {\r
 111         /* Simulate the stack frame as it would be created by a context switch\r
 112         interrupt. */\r
 113         *pxTopOfStack = portINITIAL_XPSR;       /* xPSR */\r
 114         pxTopOfStack--;\r
 115         *pxTopOfStack = ( portSTACK_TYPE ) pxCode;      /* PC */\r
 116         pxTopOfStack--;\r
 117         *pxTopOfStack = 0;      /* LR */\r
 118         pxTopOfStack -= 5;      /* R12, R3, R2 and R1. */\r
 119         *pxTopOfStack = ( portSTACK_TYPE ) pvParameters;        /* R0 */\r
 120         pxTopOfStack -= 8;      /* R11, R10, R9, R8, R7, R6, R5 and R4. */\r
 121 \r
 122         return pxTopOfStack;\r
 123 }\r
 124 /*-----------------------------------------------------------*/\r
 125 \r
 126 void vPortSVCHandler( void )\r
 127 {\r
 128         __asm volatile (\r
 129                                         "       ldr     r3, pxCurrentTCBConst2          \n" /* Restore the context. */\r
 130                                         "       ldr r1, [r3]                                    \n" /* Use pxCurrentTCBConst to get the pxCurrentTCB address. */\r
 131                                         "       ldr r0, [r1]                                    \n" /* The first item in pxCurrentTCB is the task top of stack. */\r
 132                                         "       ldmia r0!, {r4-r11}                             \n" /* Pop the registers that are not automatically saved on exception entry and the critical nesting count. */\r
 133                                         "       msr psp, r0                                             \n" /* Restore the task stack pointer. */\r
 134                                         "       mov r0, #0                                              \n"\r
 135                                         "       msr     basepri, r0                                     \n"\r
 136                                         "       orr r14, #0xd                                   \n"\r
 137                                         "       bx r14                                                  \n"\r
 138                                         "                                                                       \n"\r
 139                                         "       .align 2                                                \n"\r
 140                                         "pxCurrentTCBConst2: .word pxCurrentTCB                         \n"\r
 141                                 );\r
 142 }\r
 143 /*-----------------------------------------------------------*/\r
 144 \r
 145 void vPortStartFirstTask( void )\r
 146 {\r
 147         __asm volatile(\r
 148                                         " ldr r0, =0xE000ED08   \n" /* Use the NVIC offset register to locate the stack. */\r
 149                                         " ldr r0, [r0]                  \n"\r
 150                                         " ldr r0, [r0]                  \n"\r
 151                                         " msr msp, r0                   \n" /* Set the msp back to the start of the stack. */\r
 152                                         " svc 0                                 \n" /* System call to start first task. */\r
 153                                 );\r
 154 }\r
 155 /*-----------------------------------------------------------*/\r
 156 \r
 157 /*\r
 158  * See header file for description.\r
 159  */\r
 160 portBASE_TYPE xPortStartScheduler( void )\r
 161 {\r
 162         /* Make PendSV, CallSV and SysTick the same priroity as the kernel. */\r
 163         *(portNVIC_SYSPRI2) |= portNVIC_PENDSV_PRI;\r
 164         *(portNVIC_SYSPRI2) |= portNVIC_SYSTICK_PRI;\r
 165 \r
 166         /* Start the timer that generates the tick ISR.  Interrupts are disabled\r
 167         here already. */\r
 168         prvSetupTimerInterrupt();\r
 169 \r
 170         /* Initialise the critical nesting count ready for the first task. */\r
 171         uxCriticalNesting = 0;\r
 172 \r
 173         /* Start the first task. */\r
 174         vPortStartFirstTask();\r
 175 \r
 176         /* Should not get here! */\r
 177         return 0;\r
 178 }\r
 179 /*-----------------------------------------------------------*/\r
 180 \r
 181 void vPortEndScheduler( void )\r
 182 {\r
 183         /* It is unlikely that the CM3 port will require this function as there\r
 184         is nothing to return to.  */\r
 185 }\r
 186 /*-----------------------------------------------------------*/\r
 187 \r
 188 void vPortYieldFromISR( void )\r
 189 {\r
 190         /* Set a PendSV to request a context switch. */\r
 191         *(portNVIC_INT_CTRL) = portNVIC_PENDSVSET;\r
 192 }\r
 193 /*-----------------------------------------------------------*/\r
 194 \r
 195 void vPortEnterCritical( void )\r
 196 {\r
 197         portDISABLE_INTERRUPTS();\r
 198         uxCriticalNesting++;\r
 199 }\r
 200 /*-----------------------------------------------------------*/\r
 201 \r
 202 void vPortExitCritical( void )\r
 203 {\r
 204         uxCriticalNesting--;\r
 205         if( uxCriticalNesting == 0 )\r
 206         {\r
 207                 portENABLE_INTERRUPTS();\r
 208         }\r
 209 }\r
 210 /*-----------------------------------------------------------*/\r
 211 \r
 212 void xPortPendSVHandler( void )\r
 213 {\r
 214         /* This is a naked function. */\r
 215 \r
 216         __asm volatile\r
 217         (\r
 218         "       mrs r0, psp                                                     \n"\r
 219         "                                                                               \n"\r
 220         "       ldr     r3, pxCurrentTCBConst                   \n" /* Get the location of the current TCB. */\r
 221         "       ldr     r2, [r3]                                                \n"\r
 222         "                                                                               \n"\r
 223         "       stmdb r0!, {r4-r11}                                     \n" /* Save the remaining registers. */\r
 224         "       str r0, [r2]                                            \n" /* Save the new top of stack into the first member of the TCB. */\r
 225         "                                                                               \n"\r
 226         "       stmdb sp!, {r3, r14}                            \n"\r
 227         "       mov r0, %0                                                      \n"\r
 228         "       msr basepri, r0                                         \n"\r
 229         "       bl vTaskSwitchContext                           \n"\r
 230         "       mov r0, #0                                                      \n"\r
 231         "       msr basepri, r0                                         \n"\r
 232         "       ldmia sp!, {r3, r14}                            \n"\r
 233         "                                                                               \n"     /* Restore the context, including the critical nesting count. */\r
 234         "       ldr r1, [r3]                                            \n"\r
 235         "       ldr r0, [r1]                                            \n" /* The first item in pxCurrentTCB is the task top of stack. */\r
 236         "       ldmia r0!, {r4-r11}                                     \n" /* Pop the registers. */\r
 237         "       msr psp, r0                                                     \n"\r
 238         "       bx r14                                                          \n"\r
 239         "                                                                               \n"\r
 240         "       .align 2                                                        \n"\r
 241         "pxCurrentTCBConst: .word pxCurrentTCB  \n"\r
 242         ::"i"(configMAX_SYSCALL_INTERRUPT_PRIORITY)\r
 243         );\r
 244 }\r
 245 /*-----------------------------------------------------------*/\r
 246 \r
 247 void xPortSysTickHandler( void )\r
 248 {\r
 249 unsigned long ulDummy;\r
 250 \r
 251         /* If using preemption, also force a context switch. */\r
 252         #if configUSE_PREEMPTION == 1\r
 253                 *(portNVIC_INT_CTRL) = portNVIC_PENDSVSET;\r
 254         #endif\r
 255 \r
 256         ulDummy = portSET_INTERRUPT_MASK_FROM_ISR();\r
 257         {\r
 258                 vTaskIncrementTick();\r
 259         }\r
 260         portCLEAR_INTERRUPT_MASK_FROM_ISR( ulDummy );\r
 261 }\r
 262 /*-----------------------------------------------------------*/\r
 263 \r
 264 /*\r
 265  * Setup the systick timer to generate the tick interrupts at the required\r
 266  * frequency.\r
 267  */\r
 268 void prvSetupTimerInterrupt( void )\r
 269 {\r
 270         /* Configure SysTick to interrupt at the requested rate. */\r
 271         *(portNVIC_SYSTICK_LOAD) = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;\r
 272         *(portNVIC_SYSTICK_CTRL) = portNVIC_SYSTICK_CLK | portNVIC_SYSTICK_INT | portNVIC_SYSTICK_ENABLE;\r
 273 }\r
 274 /*-----------------------------------------------------------*/\r
 275 \r