2 * FreeRTOS Kernel V10.0.0
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3 * Copyright (C) 2017 Amazon.com, Inc. or its affiliates. All Rights Reserved.
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5 * Permission is hereby granted, free of charge, to any person obtaining a copy of
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6 * this software and associated documentation files (the "Software"), to deal in
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7 * the Software without restriction, including without limitation the rights to
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8 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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9 * the Software, and to permit persons to whom the Software is furnished to do so,
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10 * subject to the following conditions:
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12 * The above copyright notice and this permission notice shall be included in all
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13 * copies or substantial portions of the Software. If you wish to use our Amazon
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14 * FreeRTOS name, please do so in a fair use way that does not cause confusion.
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16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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18 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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19 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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20 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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21 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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23 * http://www.FreeRTOS.org
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24 * http://aws.amazon.com/freertos
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26 * 1 tab == 4 spaces!
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29 /*-----------------------------------------------------------
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30 * Implementation of functions defined in portable.h for the Atmel ARM7 port.
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31 *----------------------------------------------------------*/
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34 /* Standard includes. */
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37 /* Scheduler includes. */
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38 #include "FreeRTOS.h"
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41 /* Constants required to setup the initial stack. */
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42 #define portINITIAL_SPSR ( ( StackType_t ) 0x1f ) /* System mode, ARM mode, interrupts enabled. */
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43 #define portTHUMB_MODE_BIT ( ( StackType_t ) 0x20 )
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44 #define portINSTRUCTION_SIZE ( ( StackType_t ) 4 )
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46 /* Constants required to setup the PIT. */
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47 #define portPIT_CLOCK_DIVISOR ( ( uint32_t ) 16 )
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48 #define portPIT_COUNTER_VALUE ( ( ( configCPU_CLOCK_HZ / portPIT_CLOCK_DIVISOR ) / 1000UL ) * portTICK_PERIOD_MS )
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50 /* Constants required to handle critical sections. */
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51 #define portNO_CRITICAL_NESTING ( ( uint32_t ) 0 )
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54 #define portINT_LEVEL_SENSITIVE 0
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55 #define portPIT_ENABLE ( ( uint16_t ) 0x1 << 24 )
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56 #define portPIT_INT_ENABLE ( ( uint16_t ) 0x1 << 25 )
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57 /*-----------------------------------------------------------*/
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59 /* Setup the PIT to generate the tick interrupts. */
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60 static void prvSetupTimerInterrupt( void );
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62 /* ulCriticalNesting will get set to zero when the first task starts. It
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63 cannot be initialised to 0 as this will cause interrupts to be enabled
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64 during the kernel initialisation process. */
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65 uint32_t ulCriticalNesting = ( uint32_t ) 9999;
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67 /*-----------------------------------------------------------*/
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70 * Initialise the stack of a task to look exactly as if a call to
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71 * portSAVE_CONTEXT had been called.
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73 * See header file for description.
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75 StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
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77 StackType_t *pxOriginalTOS;
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79 pxOriginalTOS = pxTopOfStack;
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81 /* To ensure asserts in tasks.c don't fail, although in this case the assert
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82 is not really required. */
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85 /* Setup the initial stack of the task. The stack is set exactly as
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86 expected by the portRESTORE_CONTEXT() macro. */
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88 /* First on the stack is the return address - which in this case is the
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89 start of the task. The offset is added to make the return address appear
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90 as it would within an IRQ ISR. */
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91 *pxTopOfStack = ( StackType_t ) pxCode + portINSTRUCTION_SIZE;
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94 *pxTopOfStack = ( StackType_t ) 0xaaaaaaaa; /* R14 */
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96 *pxTopOfStack = ( StackType_t ) pxOriginalTOS; /* Stack used when task starts goes in R13. */
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98 *pxTopOfStack = ( StackType_t ) 0x12121212; /* R12 */
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100 *pxTopOfStack = ( StackType_t ) 0x11111111; /* R11 */
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102 *pxTopOfStack = ( StackType_t ) 0x10101010; /* R10 */
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104 *pxTopOfStack = ( StackType_t ) 0x09090909; /* R9 */
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106 *pxTopOfStack = ( StackType_t ) 0x08080808; /* R8 */
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108 *pxTopOfStack = ( StackType_t ) 0x07070707; /* R7 */
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110 *pxTopOfStack = ( StackType_t ) 0x06060606; /* R6 */
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112 *pxTopOfStack = ( StackType_t ) 0x05050505; /* R5 */
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114 *pxTopOfStack = ( StackType_t ) 0x04040404; /* R4 */
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116 *pxTopOfStack = ( StackType_t ) 0x03030303; /* R3 */
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118 *pxTopOfStack = ( StackType_t ) 0x02020202; /* R2 */
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120 *pxTopOfStack = ( StackType_t ) 0x01010101; /* R1 */
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123 /* When the task starts is will expect to find the function parameter in
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125 *pxTopOfStack = ( StackType_t ) pvParameters; /* R0 */
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128 /* The status register is set for system mode, with interrupts enabled. */
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129 *pxTopOfStack = ( StackType_t ) portINITIAL_SPSR;
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131 if( ( ( uint32_t ) pxCode & 0x01UL ) != 0x00UL )
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133 /* We want the task to start in thumb mode. */
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134 *pxTopOfStack |= portTHUMB_MODE_BIT;
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139 /* Interrupt flags cannot always be stored on the stack and will
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140 instead be stored in a variable, which is then saved as part of the
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142 *pxTopOfStack = portNO_CRITICAL_NESTING;
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144 return pxTopOfStack;
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146 /*-----------------------------------------------------------*/
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148 BaseType_t xPortStartScheduler( void )
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150 extern void vPortStartFirstTask( void );
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152 /* Start the timer that generates the tick ISR. Interrupts are disabled
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154 prvSetupTimerInterrupt();
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156 /* Start the first task. */
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157 vPortStartFirstTask();
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159 /* Should not get here! */
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162 /*-----------------------------------------------------------*/
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164 void vPortEndScheduler( void )
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166 /* It is unlikely that the ARM port will require this function as there
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167 is nothing to return to. */
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169 /*-----------------------------------------------------------*/
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171 #if configUSE_PREEMPTION == 0
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173 /* The cooperative scheduler requires a normal IRQ service routine to
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174 simply increment the system tick. */
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175 static __arm __irq void vPortNonPreemptiveTick( void );
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176 static __arm __irq void vPortNonPreemptiveTick( void )
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180 /* Increment the tick count - which may wake some tasks but as the
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181 preemptive scheduler is not being used any woken task is not given
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182 processor time no matter what its priority. */
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183 xTaskIncrementTick();
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185 /* Clear the PIT interrupt. */
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186 ulDummy = AT91C_BASE_PITC->PITC_PIVR;
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188 /* End the interrupt in the AIC. */
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189 AT91C_BASE_AIC->AIC_EOICR = ulDummy;
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194 /* Currently the IAR port requires the preemptive tick function to be
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195 defined in an asm file. */
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199 /*-----------------------------------------------------------*/
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201 static void prvSetupTimerInterrupt( void )
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203 AT91PS_PITC pxPIT = AT91C_BASE_PITC;
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205 /* Setup the AIC for PIT interrupts. The interrupt routine chosen depends
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206 on whether the preemptive or cooperative scheduler is being used. */
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207 #if configUSE_PREEMPTION == 0
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209 AT91F_AIC_ConfigureIt( AT91C_BASE_AIC, AT91C_ID_SYS, AT91C_AIC_PRIOR_HIGHEST, portINT_LEVEL_SENSITIVE, ( void (*)(void) ) vPortNonPreemptiveTick );
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213 extern void ( vPortPreemptiveTick )( void );
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214 AT91F_AIC_ConfigureIt( AT91C_BASE_AIC, AT91C_ID_SYS, AT91C_AIC_PRIOR_HIGHEST, portINT_LEVEL_SENSITIVE, ( void (*)(void) ) vPortPreemptiveTick );
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218 /* Configure the PIT period. */
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219 pxPIT->PITC_PIMR = portPIT_ENABLE | portPIT_INT_ENABLE | portPIT_COUNTER_VALUE;
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221 /* Enable the interrupt. Global interrupts are disables at this point so
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223 AT91F_AIC_EnableIt( AT91C_BASE_AIC, AT91C_ID_SYS );
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225 /*-----------------------------------------------------------*/
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227 void vPortEnterCritical( void )
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229 /* Disable interrupts first! */
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230 __disable_interrupt();
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232 /* Now interrupts are disabled ulCriticalNesting can be accessed
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233 directly. Increment ulCriticalNesting to keep a count of how many times
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234 portENTER_CRITICAL() has been called. */
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235 ulCriticalNesting++;
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237 /*-----------------------------------------------------------*/
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239 void vPortExitCritical( void )
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241 if( ulCriticalNesting > portNO_CRITICAL_NESTING )
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243 /* Decrement the nesting count as we are leaving a critical section. */
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244 ulCriticalNesting--;
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246 /* If the nesting level has reached zero then interrupts should be
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248 if( ulCriticalNesting == portNO_CRITICAL_NESTING )
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250 __enable_interrupt();
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254 /*-----------------------------------------------------------*/
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