2 FreeRTOS V6.1.0 - Copyright (C) 2010 Real Time Engineers Ltd.
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4 ***************************************************************************
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8 * + New to FreeRTOS, *
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9 * + Wanting to learn FreeRTOS or multitasking in general quickly *
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10 * + Looking for basic training, *
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11 * + Wanting to improve your FreeRTOS skills and productivity *
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13 * then take a look at the FreeRTOS books - available as PDF or paperback *
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15 * "Using the FreeRTOS Real Time Kernel - a Practical Guide" *
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16 * http://www.FreeRTOS.org/Documentation *
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18 * A pdf reference manual is also available. Both are usually delivered *
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19 * to your inbox within 20 minutes to two hours when purchased between 8am *
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20 * and 8pm GMT (although please allow up to 24 hours in case of *
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21 * exceptional circumstances). Thank you for your support! *
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23 ***************************************************************************
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25 This file is part of the FreeRTOS distribution.
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27 FreeRTOS is free software; you can redistribute it and/or modify it under
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28 the terms of the GNU General Public License (version 2) as published by the
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29 Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
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30 ***NOTE*** The exception to the GPL is included to allow you to distribute
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31 a combined work that includes FreeRTOS without being obliged to provide the
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32 source code for proprietary components outside of the FreeRTOS kernel.
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33 FreeRTOS is distributed in the hope that it will be useful, but WITHOUT
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34 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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35 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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36 more details. You should have received a copy of the GNU General Public
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37 License and the FreeRTOS license exception along with FreeRTOS; if not it
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38 can be viewed here: http://www.freertos.org/a00114.html and also obtained
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39 by writing to Richard Barry, contact details for whom are available on the
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44 http://www.FreeRTOS.org - Documentation, latest information, license and
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47 http://www.SafeRTOS.com - A version that is certified for use in safety
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50 http://www.OpenRTOS.com - Commercial support, development, porting,
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51 licensing and training services.
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54 /*-----------------------------------------------------------
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55 * Implementation of functions defined in portable.h for the ARM CM3 port.
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56 *----------------------------------------------------------*/
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58 /* Scheduler includes. */
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59 #include "FreeRTOS.h"
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62 /* For backward compatibility, ensure configKERNEL_INTERRUPT_PRIORITY is
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63 defined. The value should also ensure backward compatibility.
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64 FreeRTOS.org versions prior to V4.4.0 did not include this definition. */
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65 #ifndef configKERNEL_INTERRUPT_PRIORITY
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66 #define configKERNEL_INTERRUPT_PRIORITY 255
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69 /* Constants required to manipulate the NVIC. */
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70 #define portNVIC_SYSTICK_CTRL ( ( volatile unsigned long *) 0xe000e010 )
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71 #define portNVIC_SYSTICK_LOAD ( ( volatile unsigned long *) 0xe000e014 )
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72 #define portNVIC_INT_CTRL ( ( volatile unsigned long *) 0xe000ed04 )
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73 #define portNVIC_SYSPRI2 ( ( volatile unsigned long *) 0xe000ed20 )
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74 #define portNVIC_SYSTICK_CLK 0x00000004
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75 #define portNVIC_SYSTICK_INT 0x00000002
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76 #define portNVIC_SYSTICK_ENABLE 0x00000001
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77 #define portNVIC_PENDSVSET 0x10000000
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78 #define portNVIC_PENDSV_PRI ( ( ( unsigned long ) configKERNEL_INTERRUPT_PRIORITY ) << 16 )
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79 #define portNVIC_SYSTICK_PRI ( ( ( unsigned long ) configKERNEL_INTERRUPT_PRIORITY ) << 24 )
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81 /* Constants required to set up the initial stack. */
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82 #define portINITIAL_XPSR ( 0x01000000 )
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84 /* The priority used by the kernel is assigned to a variable to make access
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85 from inline assembler easier. */
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86 const unsigned long ulKernelPriority = configKERNEL_INTERRUPT_PRIORITY;
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88 /* Each task maintains its own interrupt status in the critical nesting
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90 static unsigned portBASE_TYPE uxCriticalNesting = 0xaaaaaaaa;
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93 * Setup the timer to generate the tick interrupts.
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95 static void prvSetupTimerInterrupt( void );
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98 * Exception handlers.
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100 void xPortPendSVHandler( void ) __attribute__ (( naked ));
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101 void xPortSysTickHandler( void );
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102 void vPortSVCHandler( void ) __attribute__ (( naked ));
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105 * Start first task is a separate function so it can be tested in isolation.
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107 void vPortStartFirstTask( void ) __attribute__ (( naked ));
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109 /*-----------------------------------------------------------*/
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112 * See header file for description.
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114 portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
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116 /* Simulate the stack frame as it would be created by a context switch
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118 pxTopOfStack--; /* Offset added to account for the way the MCU uses the stack on entry/exit of interrupts. */
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119 *pxTopOfStack = portINITIAL_XPSR; /* xPSR */
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121 *pxTopOfStack = ( portSTACK_TYPE ) pxCode; /* PC */
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123 *pxTopOfStack = 0; /* LR */
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124 pxTopOfStack -= 5; /* R12, R3, R2 and R1. */
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125 *pxTopOfStack = ( portSTACK_TYPE ) pvParameters; /* R0 */
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126 pxTopOfStack -= 8; /* R11, R10, R9, R8, R7, R6, R5 and R4. */
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128 return pxTopOfStack;
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130 /*-----------------------------------------------------------*/
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132 void vPortSVCHandler( void )
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135 " ldr r3, pxCurrentTCBConst2 \n" /* Restore the context. */
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136 " ldr r1, [r3] \n" /* Use pxCurrentTCBConst to get the pxCurrentTCB address. */
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137 " ldr r0, [r1] \n" /* The first item in pxCurrentTCB is the task top of stack. */
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138 " ldmia r0!, {r4-r11} \n" /* Pop the registers that are not automatically saved on exception entry and the critical nesting count. */
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139 " msr psp, r0 \n" /* Restore the task stack pointer. */
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141 " msr basepri, r0 \n"
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142 " orr r14, #0xd \n"
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146 "pxCurrentTCBConst2: .word pxCurrentTCB \n"
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149 /*-----------------------------------------------------------*/
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151 void vPortStartFirstTask( void )
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154 " ldr r0, =0xE000ED08 \n" /* Use the NVIC offset register to locate the stack. */
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157 " msr msp, r0 \n" /* Set the msp back to the start of the stack. */
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159 " svc 0 \n" /* System call to start first task. */
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163 /*-----------------------------------------------------------*/
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166 * See header file for description.
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168 portBASE_TYPE xPortStartScheduler( void )
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170 /* Make PendSV, CallSV and SysTick the same priroity as the kernel. */
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171 *(portNVIC_SYSPRI2) |= portNVIC_PENDSV_PRI;
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172 *(portNVIC_SYSPRI2) |= portNVIC_SYSTICK_PRI;
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174 /* Start the timer that generates the tick ISR. Interrupts are disabled
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176 prvSetupTimerInterrupt();
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178 /* Initialise the critical nesting count ready for the first task. */
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179 uxCriticalNesting = 0;
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181 /* Start the first task. */
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182 vPortStartFirstTask();
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184 /* Should not get here! */
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187 /*-----------------------------------------------------------*/
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189 void vPortEndScheduler( void )
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191 /* It is unlikely that the CM3 port will require this function as there
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192 is nothing to return to. */
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194 /*-----------------------------------------------------------*/
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196 void vPortYieldFromISR( void )
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198 /* Set a PendSV to request a context switch. */
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199 *(portNVIC_INT_CTRL) = portNVIC_PENDSVSET;
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201 /*-----------------------------------------------------------*/
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203 void vPortEnterCritical( void )
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205 portDISABLE_INTERRUPTS();
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206 uxCriticalNesting++;
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208 /*-----------------------------------------------------------*/
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210 void vPortExitCritical( void )
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212 uxCriticalNesting--;
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213 if( uxCriticalNesting == 0 )
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215 portENABLE_INTERRUPTS();
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218 /*-----------------------------------------------------------*/
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220 void xPortPendSVHandler( void )
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222 /* This is a naked function. */
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228 " ldr r3, pxCurrentTCBConst \n" /* Get the location of the current TCB. */
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231 " stmdb r0!, {r4-r11} \n" /* Save the remaining registers. */
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232 " str r0, [r2] \n" /* Save the new top of stack into the first member of the TCB. */
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234 " stmdb sp!, {r3, r14} \n"
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236 " msr basepri, r0 \n"
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237 " bl vTaskSwitchContext \n"
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239 " msr basepri, r0 \n"
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240 " ldmia sp!, {r3, r14} \n"
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241 " \n" /* Restore the context, including the critical nesting count. */
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243 " ldr r0, [r1] \n" /* The first item in pxCurrentTCB is the task top of stack. */
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244 " ldmia r0!, {r4-r11} \n" /* Pop the registers. */
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249 "pxCurrentTCBConst: .word pxCurrentTCB \n"
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250 ::"i"(configMAX_SYSCALL_INTERRUPT_PRIORITY)
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253 /*-----------------------------------------------------------*/
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255 void xPortSysTickHandler( void )
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257 unsigned long ulDummy;
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259 /* If using preemption, also force a context switch. */
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260 #if configUSE_PREEMPTION == 1
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261 *(portNVIC_INT_CTRL) = portNVIC_PENDSVSET;
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264 ulDummy = portSET_INTERRUPT_MASK_FROM_ISR();
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266 vTaskIncrementTick();
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268 portCLEAR_INTERRUPT_MASK_FROM_ISR( ulDummy );
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270 /*-----------------------------------------------------------*/
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273 * Setup the systick timer to generate the tick interrupts at the required
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276 void prvSetupTimerInterrupt( void )
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278 /* Configure SysTick to interrupt at the requested rate. */
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279 *(portNVIC_SYSTICK_LOAD) = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;
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280 *(portNVIC_SYSTICK_CTRL) = portNVIC_SYSTICK_CLK | portNVIC_SYSTICK_INT | portNVIC_SYSTICK_ENABLE;
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282 /*-----------------------------------------------------------*/
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