2 FreeRTOS.org V5.4.0 - Copyright (C) 2003-2009 Richard Barry.
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4 This file is part of the FreeRTOS.org distribution.
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6 FreeRTOS.org is free software; you can redistribute it and/or modify it
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7 under the terms of the GNU General Public License (version 2) as published
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8 by the Free Software Foundation and modified by the FreeRTOS exception.
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9 **NOTE** The exception to the GPL is included to allow you to distribute a
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10 combined work that includes FreeRTOS.org without being obliged to provide
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11 the source code for any proprietary components. Alternative commercial
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12 license and support terms are also available upon request. See the
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13 licensing section of http://www.FreeRTOS.org for full details.
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15 FreeRTOS.org is distributed in the hope that it will be useful, but WITHOUT
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16 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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17 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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20 You should have received a copy of the GNU General Public License along
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21 with FreeRTOS.org; if not, write to the Free Software Foundation, Inc., 59
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22 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
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25 ***************************************************************************
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27 * Get the FreeRTOS eBook! See http://www.FreeRTOS.org/Documentation *
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29 * This is a concise, step by step, 'hands on' guide that describes both *
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30 * general multitasking concepts and FreeRTOS specifics. It presents and *
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31 * explains numerous examples that are written using the FreeRTOS API. *
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32 * Full source code for all the examples is provided in an accompanying *
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35 ***************************************************************************
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39 Please ensure to read the configuration and relevant port sections of the
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40 online documentation.
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42 http://www.FreeRTOS.org - Documentation, latest information, license and
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45 http://www.SafeRTOS.com - A version that is certified for use in safety
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48 http://www.OpenRTOS.com - Commercial support, development, porting,
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49 licensing and training services.
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52 /*-----------------------------------------------------------
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53 * Implementation of functions defined in portable.h for the ARM CM3 port.
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54 *----------------------------------------------------------*/
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56 /* Scheduler includes. */
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57 #include "FreeRTOS.h"
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60 /* For backward compatibility, ensure configKERNEL_INTERRUPT_PRIORITY is
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61 defined. The value should also ensure backward compatibility.
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62 FreeRTOS.org versions prior to V4.4.0 did not include this definition. */
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63 #ifndef configKERNEL_INTERRUPT_PRIORITY
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64 #define configKERNEL_INTERRUPT_PRIORITY 255
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67 /* Constants required to manipulate the NVIC. */
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68 #define portNVIC_SYSTICK_CTRL ( ( volatile unsigned portLONG *) 0xe000e010 )
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69 #define portNVIC_SYSTICK_LOAD ( ( volatile unsigned portLONG *) 0xe000e014 )
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70 #define portNVIC_INT_CTRL ( ( volatile unsigned portLONG *) 0xe000ed04 )
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71 #define portNVIC_SYSPRI2 ( ( volatile unsigned portLONG *) 0xe000ed20 )
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72 #define portNVIC_SYSTICK_CLK 0x00000004
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73 #define portNVIC_SYSTICK_INT 0x00000002
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74 #define portNVIC_SYSTICK_ENABLE 0x00000001
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75 #define portNVIC_PENDSVSET 0x10000000
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76 #define portNVIC_PENDSV_PRI ( ( ( unsigned portLONG ) configKERNEL_INTERRUPT_PRIORITY ) << 16 )
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77 #define portNVIC_SYSTICK_PRI ( ( ( unsigned portLONG ) configKERNEL_INTERRUPT_PRIORITY ) << 24 )
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79 /* Constants required to set up the initial stack. */
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80 #define portINITIAL_XPSR ( 0x01000000 )
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82 /* The priority used by the kernel is assigned to a variable to make access
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83 from inline assembler easier. */
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84 const unsigned portLONG ulKernelPriority = configKERNEL_INTERRUPT_PRIORITY;
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86 /* Each task maintains its own interrupt status in the critical nesting
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88 static unsigned portBASE_TYPE uxCriticalNesting = 0xaaaaaaaa;
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91 * Setup the timer to generate the tick interrupts.
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93 static void prvSetupTimerInterrupt( void );
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96 * Exception handlers.
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98 void xPortPendSVHandler( void ) __attribute__ (( naked ));
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99 void xPortSysTickHandler( void );
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100 void vPortSVCHandler( void ) __attribute__ (( naked ));
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103 * Start first task is a separate function so it can be tested in isolation.
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105 void vPortStartFirstTask( void ) __attribute__ (( naked ));
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107 /*-----------------------------------------------------------*/
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110 * See header file for description.
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112 portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
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114 /* Simulate the stack frame as it would be created by a context switch
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116 *pxTopOfStack = portINITIAL_XPSR; /* xPSR */
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118 *pxTopOfStack = ( portSTACK_TYPE ) pxCode; /* PC */
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120 *pxTopOfStack = 0; /* LR */
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121 pxTopOfStack -= 5; /* R12, R3, R2 and R1. */
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122 *pxTopOfStack = ( portSTACK_TYPE ) pvParameters; /* R0 */
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123 pxTopOfStack -= 8; /* R11, R10, R9, R8, R7, R6, R5 and R4. */
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125 return pxTopOfStack;
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127 /*-----------------------------------------------------------*/
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129 void vPortSVCHandler( void )
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132 " ldr r3, pxCurrentTCBConst2 \n" /* Restore the context. */
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133 " ldr r1, [r3] \n" /* Use pxCurrentTCBConst to get the pxCurrentTCB address. */
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134 " ldr r0, [r1] \n" /* The first item in pxCurrentTCB is the task top of stack. */
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135 " 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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136 " msr psp, r0 \n" /* Restore the task stack pointer. */
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138 " msr basepri, r0 \n"
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139 " orr r14, #0xd \n"
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143 "pxCurrentTCBConst2: .word pxCurrentTCB \n"
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146 /*-----------------------------------------------------------*/
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148 void vPortStartFirstTask( void )
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151 " ldr r0, =0xE000ED08 \n" /* Use the NVIC offset register to locate the stack. */
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154 " msr msp, r0 \n" /* Set the msp back to the start of the stack. */
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155 " svc 0 \n" /* System call to start first task. */
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158 /*-----------------------------------------------------------*/
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161 * See header file for description.
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163 portBASE_TYPE xPortStartScheduler( void )
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165 /* Make PendSV, CallSV and SysTick the same priroity as the kernel. */
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166 *(portNVIC_SYSPRI2) |= portNVIC_PENDSV_PRI;
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167 *(portNVIC_SYSPRI2) |= portNVIC_SYSTICK_PRI;
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169 /* Start the timer that generates the tick ISR. Interrupts are disabled
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171 prvSetupTimerInterrupt();
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173 /* Initialise the critical nesting count ready for the first task. */
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174 uxCriticalNesting = 0;
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176 /* Start the first task. */
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177 vPortStartFirstTask();
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179 /* Should not get here! */
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182 /*-----------------------------------------------------------*/
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184 void vPortEndScheduler( void )
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186 /* It is unlikely that the CM3 port will require this function as there
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187 is nothing to return to. */
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189 /*-----------------------------------------------------------*/
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191 void vPortYieldFromISR( void )
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193 /* Set a PendSV to request a context switch. */
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194 *(portNVIC_INT_CTRL) = portNVIC_PENDSVSET;
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196 /*-----------------------------------------------------------*/
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198 void vPortEnterCritical( void )
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200 portDISABLE_INTERRUPTS();
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201 uxCriticalNesting++;
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203 /*-----------------------------------------------------------*/
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205 void vPortExitCritical( void )
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207 uxCriticalNesting--;
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208 if( uxCriticalNesting == 0 )
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210 portENABLE_INTERRUPTS();
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213 /*-----------------------------------------------------------*/
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215 void xPortPendSVHandler( void )
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217 /* This is a naked function. */
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223 " ldr r3, pxCurrentTCBConst \n" /* Get the location of the current TCB. */
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226 " stmdb r0!, {r4-r11} \n" /* Save the remaining registers. */
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227 " str r0, [r2] \n" /* Save the new top of stack into the first member of the TCB. */
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229 " stmdb sp!, {r3, r14} \n"
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231 " msr basepri, r0 \n"
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232 " bl vTaskSwitchContext \n"
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234 " msr basepri, r0 \n"
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235 " ldmia sp!, {r3, r14} \n"
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236 " \n" /* Restore the context, including the critical nesting count. */
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238 " ldr r0, [r1] \n" /* The first item in pxCurrentTCB is the task top of stack. */
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239 " ldmia r0!, {r4-r11} \n" /* Pop the registers. */
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244 "pxCurrentTCBConst: .word pxCurrentTCB \n"
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245 ::"i"(configMAX_SYSCALL_INTERRUPT_PRIORITY)
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248 /*-----------------------------------------------------------*/
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250 void xPortSysTickHandler( void )
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252 unsigned portLONG ulDummy;
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254 /* If using preemption, also force a context switch. */
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255 #if configUSE_PREEMPTION == 1
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256 *(portNVIC_INT_CTRL) = portNVIC_PENDSVSET;
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259 ulDummy = portSET_INTERRUPT_MASK_FROM_ISR();
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261 vTaskIncrementTick();
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263 portCLEAR_INTERRUPT_MASK_FROM_ISR( ulDummy );
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265 /*-----------------------------------------------------------*/
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268 * Setup the systick timer to generate the tick interrupts at the required
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271 void prvSetupTimerInterrupt( void )
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273 /* Configure SysTick to interrupt at the requested rate. */
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274 *(portNVIC_SYSTICK_LOAD) = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;
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275 *(portNVIC_SYSTICK_CTRL) = portNVIC_SYSTICK_CLK | portNVIC_SYSTICK_INT | portNVIC_SYSTICK_ENABLE;
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277 /*-----------------------------------------------------------*/
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