2 FreeRTOS V5.4.2 - Copyright (C) 2009 Real Time Engineers Ltd.
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4 This file is part of the FreeRTOS distribution.
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6 FreeRTOS is free software; you can redistribute it and/or modify it under
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7 the terms of the GNU General Public License (version 2) as published by the
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8 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 without being obliged to provide the
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11 source code for proprietary components outside of the FreeRTOS kernel.
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12 Alternative commercial license and support terms are also available upon
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13 request. See the licensing section of http://www.FreeRTOS.org for full
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16 FreeRTOS is distributed in the hope that it will be useful, but WITHOUT
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17 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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18 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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21 You should have received a copy of the GNU General Public License along
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22 with FreeRTOS; if not, write to the Free Software Foundation, Inc., 59
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23 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
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26 ***************************************************************************
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28 * Looking for a quick start? Then check out the FreeRTOS eBook! *
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29 * See http://www.FreeRTOS.org/Documentation for details *
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31 ***************************************************************************
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35 Please ensure to read the configuration and relevant port sections of the
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36 online documentation.
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38 http://www.FreeRTOS.org - Documentation, latest information, license and
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41 http://www.SafeRTOS.com - A version that is certified for use in safety
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44 http://www.OpenRTOS.com - Commercial support, development, porting,
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45 licensing and training services.
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48 /*-----------------------------------------------------------
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49 * Implementation of functions defined in portable.h for the Philips ARM7 port.
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50 *----------------------------------------------------------*/
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55 + Bug fix - The prescale value for the timer setup is now written to T0PR
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56 instead of T0PC. This bug would have had no effect unless a prescale
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57 value was actually used.
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60 /* Standard includes. */
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62 #include <intrinsics.h>
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64 /* Scheduler includes. */
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65 #include "FreeRTOS.h"
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68 /* Constants required to setup the tick ISR. */
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69 #define portENABLE_TIMER ( ( unsigned portCHAR ) 0x01 )
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70 #define portPRESCALE_VALUE 0x00
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71 #define portINTERRUPT_ON_MATCH ( ( unsigned portLONG ) 0x01 )
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72 #define portRESET_COUNT_ON_MATCH ( ( unsigned portLONG ) 0x02 )
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74 /* Constants required to setup the initial stack. */
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75 #define portINITIAL_SPSR ( ( portSTACK_TYPE ) 0x1f ) /* System mode, ARM mode, interrupts enabled. */
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76 #define portTHUMB_MODE_BIT ( ( portSTACK_TYPE ) 0x20 )
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77 #define portINSTRUCTION_SIZE ( ( portSTACK_TYPE ) 4 )
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79 /* Constants required to setup the PIT. */
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80 #define portPIT_CLOCK_DIVISOR ( ( unsigned portLONG ) 16 )
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81 #define portPIT_COUNTER_VALUE ( ( ( configCPU_CLOCK_HZ / portPIT_CLOCK_DIVISOR ) / 1000UL ) * portTICK_RATE_MS )
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83 /* Constants required to handle interrupts. */
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84 #define portTIMER_MATCH_ISR_BIT ( ( unsigned portCHAR ) 0x01 )
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85 #define portCLEAR_VIC_INTERRUPT ( ( unsigned portLONG ) 0 )
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87 /* Constants required to handle critical sections. */
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88 #define portNO_CRITICAL_NESTING ( ( unsigned portLONG ) 0 )
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91 #define portINT_LEVEL_SENSITIVE 0
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92 #define portPIT_ENABLE ( ( unsigned portSHORT ) 0x1 << 24 )
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93 #define portPIT_INT_ENABLE ( ( unsigned portSHORT ) 0x1 << 25 )
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95 /* Constants required to setup the VIC for the tick ISR. */
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96 #define portTIMER_VIC_CHANNEL ( ( unsigned portLONG ) 0x0004 )
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97 #define portTIMER_VIC_CHANNEL_BIT ( ( unsigned portLONG ) 0x0010 )
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98 #define portTIMER_VIC_ENABLE ( ( unsigned portLONG ) 0x0020 )
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100 /*-----------------------------------------------------------*/
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102 /* Setup the PIT to generate the tick interrupts. */
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103 static void prvSetupTimerInterrupt( void );
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105 /* ulCriticalNesting will get set to zero when the first task starts. It
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106 cannot be initialised to 0 as this will cause interrupts to be enabled
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107 during the kernel initialisation process. */
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108 unsigned portLONG ulCriticalNesting = ( unsigned portLONG ) 9999;
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110 /*-----------------------------------------------------------*/
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113 * Initialise the stack of a task to look exactly as if a call to
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114 * portSAVE_CONTEXT had been called.
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116 * See header file for description.
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118 portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
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120 portSTACK_TYPE *pxOriginalTOS;
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122 pxOriginalTOS = pxTopOfStack;
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124 /* Setup the initial stack of the task. The stack is set exactly as
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125 expected by the portRESTORE_CONTEXT() macro. */
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127 /* First on the stack is the return address - which in this case is the
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128 start of the task. The offset is added to make the return address appear
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129 as it would within an IRQ ISR. */
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130 *pxTopOfStack = ( portSTACK_TYPE ) pxCode + portINSTRUCTION_SIZE;
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133 *pxTopOfStack = ( portSTACK_TYPE ) 0xaaaaaaaa; /* R14 */
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135 *pxTopOfStack = ( portSTACK_TYPE ) pxOriginalTOS; /* Stack used when task starts goes in R13. */
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137 *pxTopOfStack = ( portSTACK_TYPE ) 0x12121212; /* R12 */
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139 *pxTopOfStack = ( portSTACK_TYPE ) 0x11111111; /* R11 */
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141 *pxTopOfStack = ( portSTACK_TYPE ) 0x10101010; /* R10 */
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143 *pxTopOfStack = ( portSTACK_TYPE ) 0x09090909; /* R9 */
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145 *pxTopOfStack = ( portSTACK_TYPE ) 0x08080808; /* R8 */
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147 *pxTopOfStack = ( portSTACK_TYPE ) 0x07070707; /* R7 */
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149 *pxTopOfStack = ( portSTACK_TYPE ) 0x06060606; /* R6 */
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151 *pxTopOfStack = ( portSTACK_TYPE ) 0x05050505; /* R5 */
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153 *pxTopOfStack = ( portSTACK_TYPE ) 0x04040404; /* R4 */
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155 *pxTopOfStack = ( portSTACK_TYPE ) 0x03030303; /* R3 */
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157 *pxTopOfStack = ( portSTACK_TYPE ) 0x02020202; /* R2 */
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159 *pxTopOfStack = ( portSTACK_TYPE ) 0x01010101; /* R1 */
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162 /* When the task starts is will expect to find the function parameter in
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164 *pxTopOfStack = ( portSTACK_TYPE ) pvParameters; /* R0 */
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167 /* The status register is set for system mode, with interrupts enabled. */
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168 *pxTopOfStack = ( portSTACK_TYPE ) portINITIAL_SPSR;
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170 if( ( ( unsigned long ) pxCode & 0x01UL ) != 0x00UL )
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172 /* We want the task to start in thumb mode. */
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173 *pxTopOfStack |= portTHUMB_MODE_BIT;
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178 /* Interrupt flags cannot always be stored on the stack and will
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179 instead be stored in a variable, which is then saved as part of the
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181 *pxTopOfStack = portNO_CRITICAL_NESTING;
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183 return pxTopOfStack;
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185 /*-----------------------------------------------------------*/
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187 portBASE_TYPE xPortStartScheduler( void )
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189 extern void vPortStartFirstTask( void );
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191 /* Start the timer that generates the tick ISR. Interrupts are disabled
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193 prvSetupTimerInterrupt();
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195 /* Start the first task. */
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196 vPortStartFirstTask();
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198 /* Should not get here! */
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201 /*-----------------------------------------------------------*/
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203 void vPortEndScheduler( void )
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205 /* It is unlikely that the ARM port will require this function as there
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206 is nothing to return to. */
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208 /*-----------------------------------------------------------*/
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210 #if configUSE_PREEMPTION == 0
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212 /* The cooperative scheduler requires a normal IRQ service routine to
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213 simply increment the system tick. */
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214 static __arm __irq void vPortNonPreemptiveTick( void );
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215 static __arm __irq void vPortNonPreemptiveTick( void )
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217 /* Increment the tick count - which may wake some tasks but as the
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218 preemptive scheduler is not being used any woken task is not given
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219 processor time no matter what its priority. */
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220 vTaskIncrementTick();
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222 /* Ready for the next interrupt. */
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223 T0IR = portTIMER_MATCH_ISR_BIT;
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224 VICVectAddr = portCLEAR_VIC_INTERRUPT;
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229 /* This function is called from an asm wrapper, so does not require the __irq
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231 void vPortPreemptiveTick( void );
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232 void vPortPreemptiveTick( void )
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234 /* Increment the tick counter. */
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235 vTaskIncrementTick();
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237 /* The new tick value might unblock a task. Ensure the highest task that
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238 is ready to execute is the task that will execute when the tick ISR
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240 vTaskSwitchContext();
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242 /* Ready for the next interrupt. */
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243 T0IR = portTIMER_MATCH_ISR_BIT;
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244 VICVectAddr = portCLEAR_VIC_INTERRUPT;
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249 /*-----------------------------------------------------------*/
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251 static void prvSetupTimerInterrupt( void )
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253 unsigned portLONG ulCompareMatch;
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255 /* A 1ms tick does not require the use of the timer prescale. This is
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256 defaulted to zero but can be used if necessary. */
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257 T0PR = portPRESCALE_VALUE;
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259 /* Calculate the match value required for our wanted tick rate. */
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260 ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;
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262 /* Protect against divide by zero. Using an if() statement still results
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263 in a warning - hence the #if. */
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264 #if portPRESCALE_VALUE != 0
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266 ulCompareMatch /= ( portPRESCALE_VALUE + 1 );
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270 T0MR0 = ulCompareMatch;
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272 /* Generate tick with timer 0 compare match. */
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273 T0MCR = portRESET_COUNT_ON_MATCH | portINTERRUPT_ON_MATCH;
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275 /* Setup the VIC for the timer. */
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276 VICIntSelect &= ~( portTIMER_VIC_CHANNEL_BIT );
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277 VICIntEnable |= portTIMER_VIC_CHANNEL_BIT;
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279 /* The ISR installed depends on whether the preemptive or cooperative
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280 scheduler is being used. */
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281 #if configUSE_PREEMPTION == 1
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283 extern void ( vPortPreemptiveTickEntry )( void );
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285 VICVectAddr0 = ( unsigned portLONG ) vPortPreemptiveTickEntry;
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289 extern void ( vNonPreemptiveTick )( void );
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291 VICVectAddr0 = ( portLONG ) vPortNonPreemptiveTick;
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295 VICVectCntl0 = portTIMER_VIC_CHANNEL | portTIMER_VIC_ENABLE;
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297 /* Start the timer - interrupts are disabled when this function is called
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298 so it is okay to do this here. */
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299 T0TCR = portENABLE_TIMER;
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301 /*-----------------------------------------------------------*/
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303 void vPortEnterCritical( void )
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305 /* Disable interrupts first! */
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306 __disable_interrupt();
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308 /* Now interrupts are disabled ulCriticalNesting can be accessed
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309 directly. Increment ulCriticalNesting to keep a count of how many times
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310 portENTER_CRITICAL() has been called. */
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311 ulCriticalNesting++;
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313 /*-----------------------------------------------------------*/
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315 void vPortExitCritical( void )
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317 if( ulCriticalNesting > portNO_CRITICAL_NESTING )
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319 /* Decrement the nesting count as we are leaving a critical section. */
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320 ulCriticalNesting--;
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322 /* If the nesting level has reached zero then interrupts should be
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324 if( ulCriticalNesting == portNO_CRITICAL_NESTING )
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326 __enable_interrupt();
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330 /*-----------------------------------------------------------*/
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