git.sur5r.net Git - freertos/blob - Source/portable/GCC/ATMega323/port.c

   1 /*\r
   2         FreeRTOS.org V4.6.1 - Copyright (C) 2003-2007 Richard Barry.\r
   3 \r
   4         This file is part of the FreeRTOS.org distribution.\r
   5 \r
   6         FreeRTOS.org is free software; you can redistribute it and/or modify\r
   7         it under the terms of the GNU General Public License as published by\r
   8         the Free Software Foundation; either version 2 of the License, or\r
   9         (at your option) any later version.\r
  10 \r
  11         FreeRTOS.org is distributed in the hope that it will be useful,\r
  12         but WITHOUT ANY WARRANTY; without even the implied warranty of\r
  13         MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the\r
  14         GNU General Public License for more details.\r
  15 \r
  16         You should have received a copy of the GNU General Public License\r
  17         along with FreeRTOS.org; if not, write to the Free Software\r
  18         Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA\r
  19 \r
  20         A special exception to the GPL can be applied should you wish to distribute\r
  21         a combined work that includes FreeRTOS.org, without being obliged to provide\r
  22         the source code for any proprietary components.  See the licensing section \r
  23         of http://www.FreeRTOS.org for full details of how and when the exception\r
  24         can be applied.\r
  25 \r
  26         ***************************************************************************\r
  27         See http://www.FreeRTOS.org for documentation, latest information, license \r
  28         and contact details.  Please ensure to read the configuration and relevant \r
  29         port sections of the online documentation.\r
  30 \r
  31         Also see http://www.SafeRTOS.com a version that has been certified for use\r
  32         in safety critical systems, plus commercial licensing, development and\r
  33         support options.\r
  34         ***************************************************************************\r
  35 */\r
  36 \r
  37 /* \r
  38 \r
  39 Changes from V2.6.0\r
  40 \r
  41         + AVR port - Replaced the inb() and outb() functions with direct memory\r
  42           access.  This allows the port to be built with the 20050414 build of\r
  43           WinAVR.\r
  44 */\r
  45 \r
  46 #include <stdlib.h>\r
  47 #include <avr/interrupt.h>\r
  48 \r
  49 #include "FreeRTOS.h"\r
  50 #include "task.h"\r
  51 \r
  52 /*-----------------------------------------------------------\r
  53  * Implementation of functions defined in portable.h for the AVR port.\r
  54  *----------------------------------------------------------*/\r
  55 \r
  56 /* Start tasks with interrupts enables. */\r
  57 #define portFLAGS_INT_ENABLED                                   ( ( portSTACK_TYPE ) 0x80 )\r
  58 \r
  59 /* Hardware constants for timer 1. */\r
  60 #define portCLEAR_COUNTER_ON_MATCH                              ( ( unsigned portCHAR ) 0x08 )\r
  61 #define portPRESCALE_64                                                 ( ( unsigned portCHAR ) 0x03 )\r
  62 #define portCLOCK_PRESCALER                                             ( ( unsigned portLONG ) 64 )\r
  63 #define portCOMPARE_MATCH_A_INTERRUPT_ENABLE    ( ( unsigned portCHAR ) 0x10 )\r
  64 \r
  65 /*-----------------------------------------------------------*/\r
  66 \r
  67 /* We require the address of the pxCurrentTCB variable, but don't want to know\r
  68 any details of its type. */\r
  69 typedef void tskTCB;\r
  70 extern volatile tskTCB * volatile pxCurrentTCB;\r
  71 \r
  72 /*-----------------------------------------------------------*/\r
  73 \r
  74 /* \r
  75  * Macro to save all the general purpose registers, the save the stack pointer\r
  76  * into the TCB.  \r
  77  * \r
  78  * The first thing we do is save the flags then disable interrupts.  This is to \r
  79  * guard our stack against having a context switch interrupt after we have already \r
  80  * pushed the registers onto the stack - causing the 32 registers to be on the \r
  81  * stack twice. \r
  82  * \r
  83  * r1 is set to zero as the compiler expects it to be thus, however some\r
  84  * of the math routines make use of R1. \r
  85  * \r
  86  * The interrupts will have been disabled during the call to portSAVE_CONTEXT()\r
  87  * so we need not worry about reading/writing to the stack pointer. \r
  88  */\r
  89 \r
  90 #define portSAVE_CONTEXT()                                                                      \\r
  91         asm volatile (  "push   r0                                              \n\t"   \\r
  92                                         "in             r0, __SREG__                    \n\t"   \\r
  93                                         "cli                                                    \n\t"   \\r
  94                                         "push   r0                                              \n\t"   \\r
  95                                         "push   r1                                              \n\t"   \\r
  96                                         "clr    r1                                              \n\t"   \\r
  97                                         "push   r2                                              \n\t"   \\r
  98                                         "push   r3                                              \n\t"   \\r
  99                                         "push   r4                                              \n\t"   \\r
 100                                         "push   r5                                              \n\t"   \\r
 101                                         "push   r6                                              \n\t"   \\r
 102                                         "push   r7                                              \n\t"   \\r
 103                                         "push   r8                                              \n\t"   \\r
 104                                         "push   r9                                              \n\t"   \\r
 105                                         "push   r10                                             \n\t"   \\r
 106                                         "push   r11                                             \n\t"   \\r
 107                                         "push   r12                                             \n\t"   \\r
 108                                         "push   r13                                             \n\t"   \\r
 109                                         "push   r14                                             \n\t"   \\r
 110                                         "push   r15                                             \n\t"   \\r
 111                                         "push   r16                                             \n\t"   \\r
 112                                         "push   r17                                             \n\t"   \\r
 113                                         "push   r18                                             \n\t"   \\r
 114                                         "push   r19                                             \n\t"   \\r
 115                                         "push   r20                                             \n\t"   \\r
 116                                         "push   r21                                             \n\t"   \\r
 117                                         "push   r22                                             \n\t"   \\r
 118                                         "push   r23                                             \n\t"   \\r
 119                                         "push   r24                                             \n\t"   \\r
 120                                         "push   r25                                             \n\t"   \\r
 121                                         "push   r26                                             \n\t"   \\r
 122                                         "push   r27                                             \n\t"   \\r
 123                                         "push   r28                                             \n\t"   \\r
 124                                         "push   r29                                             \n\t"   \\r
 125                                         "push   r30                                             \n\t"   \\r
 126                                         "push   r31                                             \n\t"   \\r
 127                                         "lds    r26, pxCurrentTCB               \n\t"   \\r
 128                                         "lds    r27, pxCurrentTCB + 1   \n\t"   \\r
 129                                         "in             r0, 0x3d                                \n\t"   \\r
 130                                         "st             x+, r0                                  \n\t"   \\r
 131                                         "in             r0, 0x3e                                \n\t"   \\r
 132                                         "st             x+, r0                                  \n\t"   \\r
 133                                 );\r
 134 \r
 135 /* \r
 136  * Opposite to portSAVE_CONTEXT().  Interrupts will have been disabled during\r
 137  * the context save so we can write to the stack pointer. \r
 138  */\r
 139 \r
 140 #define portRESTORE_CONTEXT()                                                           \\r
 141         asm volatile (  "lds    r26, pxCurrentTCB               \n\t"   \\r
 142                                         "lds    r27, pxCurrentTCB + 1   \n\t"   \\r
 143                                         "ld             r28, x+                                 \n\t"   \\r
 144                                         "out    __SP_L__, r28                   \n\t"   \\r
 145                                         "ld             r29, x+                                 \n\t"   \\r
 146                                         "out    __SP_H__, r29                   \n\t"   \\r
 147                                         "pop    r31                                             \n\t"   \\r
 148                                         "pop    r30                                             \n\t"   \\r
 149                                         "pop    r29                                             \n\t"   \\r
 150                                         "pop    r28                                             \n\t"   \\r
 151                                         "pop    r27                                             \n\t"   \\r
 152                                         "pop    r26                                             \n\t"   \\r
 153                                         "pop    r25                                             \n\t"   \\r
 154                                         "pop    r24                                             \n\t"   \\r
 155                                         "pop    r23                                             \n\t"   \\r
 156                                         "pop    r22                                             \n\t"   \\r
 157                                         "pop    r21                                             \n\t"   \\r
 158                                         "pop    r20                                             \n\t"   \\r
 159                                         "pop    r19                                             \n\t"   \\r
 160                                         "pop    r18                                             \n\t"   \\r
 161                                         "pop    r17                                             \n\t"   \\r
 162                                         "pop    r16                                             \n\t"   \\r
 163                                         "pop    r15                                             \n\t"   \\r
 164                                         "pop    r14                                             \n\t"   \\r
 165                                         "pop    r13                                             \n\t"   \\r
 166                                         "pop    r12                                             \n\t"   \\r
 167                                         "pop    r11                                             \n\t"   \\r
 168                                         "pop    r10                                             \n\t"   \\r
 169                                         "pop    r9                                              \n\t"   \\r
 170                                         "pop    r8                                              \n\t"   \\r
 171                                         "pop    r7                                              \n\t"   \\r
 172                                         "pop    r6                                              \n\t"   \\r
 173                                         "pop    r5                                              \n\t"   \\r
 174                                         "pop    r4                                              \n\t"   \\r
 175                                         "pop    r3                                              \n\t"   \\r
 176                                         "pop    r2                                              \n\t"   \\r
 177                                         "pop    r1                                              \n\t"   \\r
 178                                         "pop    r0                                              \n\t"   \\r
 179                                         "out    __SREG__, r0                    \n\t"   \\r
 180                                         "pop    r0                                              \n\t"   \\r
 181                                 );\r
 182 \r
 183 /*-----------------------------------------------------------*/\r
 184 \r
 185 /*\r
 186  * Perform hardware setup to enable ticks from timer 1, compare match A.\r
 187  */\r
 188 static void prvSetupTimerInterrupt( void );\r
 189 /*-----------------------------------------------------------*/\r
 190 \r
 191 /* \r
 192  * See header file for description. \r
 193  */\r
 194 portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )\r
 195 {\r
 196 unsigned portSHORT usAddress;\r
 197 \r
 198         /* Place a few bytes of known values on the bottom of the stack. \r
 199         This is just useful for debugging. */\r
 200 \r
 201         *pxTopOfStack = 0x11;\r
 202         pxTopOfStack--;\r
 203         *pxTopOfStack = 0x22;\r
 204         pxTopOfStack--;\r
 205         *pxTopOfStack = 0x33;\r
 206         pxTopOfStack--;\r
 207 \r
 208         /* Simulate how the stack would look after a call to vPortYield() generated by \r
 209         the compiler. */\r
 210 \r
 211         /*lint -e950 -e611 -e923 Lint doesn't like this much - but nothing I can do about it. */\r
 212 \r
 213         /* The start of the task code will be popped off the stack last, so place\r
 214         it on first. */\r
 215         usAddress = ( unsigned portSHORT ) pxCode;\r
 216         *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned portSHORT ) 0x00ff );\r
 217         pxTopOfStack--;\r
 218 \r
 219         usAddress >>= 8;\r
 220         *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned portSHORT ) 0x00ff );\r
 221         pxTopOfStack--;\r
 222 \r
 223         /* Next simulate the stack as if after a call to portSAVE_CONTEXT().  \r
 224         portSAVE_CONTEXT places the flags on the stack immediately after r0\r
 225         to ensure the interrupts get disabled as soon as possible, and so ensuring\r
 226         the stack use is minimal should a context switch interrupt occur. */\r
 227         *pxTopOfStack = ( portSTACK_TYPE ) 0x00;        /* R0 */\r
 228         pxTopOfStack--;\r
 229         *pxTopOfStack = portFLAGS_INT_ENABLED;\r
 230         pxTopOfStack--;\r
 231 \r
 232 \r
 233         /* Now the remaining registers.   The compiler expects R1 to be 0. */\r
 234         *pxTopOfStack = ( portSTACK_TYPE ) 0x00;        /* R1 */\r
 235         pxTopOfStack--;\r
 236         *pxTopOfStack = ( portSTACK_TYPE ) 0x02;        /* R2 */\r
 237         pxTopOfStack--;\r
 238         *pxTopOfStack = ( portSTACK_TYPE ) 0x03;        /* R3 */\r
 239         pxTopOfStack--;\r
 240         *pxTopOfStack = ( portSTACK_TYPE ) 0x04;        /* R4 */\r
 241         pxTopOfStack--;\r
 242         *pxTopOfStack = ( portSTACK_TYPE ) 0x05;        /* R5 */\r
 243         pxTopOfStack--;\r
 244         *pxTopOfStack = ( portSTACK_TYPE ) 0x06;        /* R6 */\r
 245         pxTopOfStack--;\r
 246         *pxTopOfStack = ( portSTACK_TYPE ) 0x07;        /* R7 */\r
 247         pxTopOfStack--;\r
 248         *pxTopOfStack = ( portSTACK_TYPE ) 0x08;        /* R8 */\r
 249         pxTopOfStack--;\r
 250         *pxTopOfStack = ( portSTACK_TYPE ) 0x09;        /* R9 */\r
 251         pxTopOfStack--;\r
 252         *pxTopOfStack = ( portSTACK_TYPE ) 0x10;        /* R10 */\r
 253         pxTopOfStack--;\r
 254         *pxTopOfStack = ( portSTACK_TYPE ) 0x11;        /* R11 */\r
 255         pxTopOfStack--;\r
 256         *pxTopOfStack = ( portSTACK_TYPE ) 0x12;        /* R12 */\r
 257         pxTopOfStack--;\r
 258         *pxTopOfStack = ( portSTACK_TYPE ) 0x13;        /* R13 */\r
 259         pxTopOfStack--;\r
 260         *pxTopOfStack = ( portSTACK_TYPE ) 0x14;        /* R14 */\r
 261         pxTopOfStack--;\r
 262         *pxTopOfStack = ( portSTACK_TYPE ) 0x15;        /* R15 */\r
 263         pxTopOfStack--;\r
 264         *pxTopOfStack = ( portSTACK_TYPE ) 0x16;        /* R16 */\r
 265         pxTopOfStack--;\r
 266         *pxTopOfStack = ( portSTACK_TYPE ) 0x17;        /* R17 */\r
 267         pxTopOfStack--;\r
 268         *pxTopOfStack = ( portSTACK_TYPE ) 0x18;        /* R18 */\r
 269         pxTopOfStack--;\r
 270         *pxTopOfStack = ( portSTACK_TYPE ) 0x19;        /* R19 */\r
 271         pxTopOfStack--;\r
 272         *pxTopOfStack = ( portSTACK_TYPE ) 0x20;        /* R20 */\r
 273         pxTopOfStack--;\r
 274         *pxTopOfStack = ( portSTACK_TYPE ) 0x21;        /* R21 */\r
 275         pxTopOfStack--;\r
 276         *pxTopOfStack = ( portSTACK_TYPE ) 0x22;        /* R22 */\r
 277         pxTopOfStack--;\r
 278         *pxTopOfStack = ( portSTACK_TYPE ) 0x23;        /* R23 */\r
 279         pxTopOfStack--;\r
 280 \r
 281         /* Place the parameter on the stack in the expected location. */\r
 282         usAddress = ( unsigned portSHORT ) pvParameters;\r
 283         *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned portSHORT ) 0x00ff );\r
 284         pxTopOfStack--;\r
 285 \r
 286         usAddress >>= 8;\r
 287         *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned portSHORT ) 0x00ff );\r
 288         pxTopOfStack--;\r
 289 \r
 290         *pxTopOfStack = ( portSTACK_TYPE ) 0x26;        /* R26 X */\r
 291         pxTopOfStack--;\r
 292         *pxTopOfStack = ( portSTACK_TYPE ) 0x27;        /* R27 */\r
 293         pxTopOfStack--;\r
 294         *pxTopOfStack = ( portSTACK_TYPE ) 0x28;        /* R28 Y */\r
 295         pxTopOfStack--;\r
 296         *pxTopOfStack = ( portSTACK_TYPE ) 0x29;        /* R29 */\r
 297         pxTopOfStack--;\r
 298         *pxTopOfStack = ( portSTACK_TYPE ) 0x30;        /* R30 Z */\r
 299         pxTopOfStack--;\r
 300         *pxTopOfStack = ( portSTACK_TYPE ) 0x031;       /* R31 */\r
 301         pxTopOfStack--;\r
 302 \r
 303         /*lint +e950 +e611 +e923 */\r
 304 \r
 305         return pxTopOfStack;\r
 306 }\r
 307 /*-----------------------------------------------------------*/\r
 308 \r
 309 portBASE_TYPE xPortStartScheduler( void )\r
 310 {\r
 311         /* In this port we ignore the parameter and use the configUSE_PREEMPTION\r
 312         definition instead. */\r
 313 \r
 314         /* Setup the hardware to generate the tick. */\r
 315         prvSetupTimerInterrupt();\r
 316 \r
 317         /* Restore the context of the first task that is going to run. */\r
 318         portRESTORE_CONTEXT();\r
 319 \r
 320         /* Simulate a function call end as generated by the compiler.  We will now\r
 321         jump to the start of the task the context of which we have just restored. */\r
 322         asm volatile ( "ret" );\r
 323 \r
 324         /* Should not get here. */\r
 325         return pdTRUE;\r
 326 }\r
 327 /*-----------------------------------------------------------*/\r
 328 \r
 329 void vPortEndScheduler( void )\r
 330 {\r
 331         /* It is unlikely that the AVR port will get stopped.  If required simply\r
 332         disable the tick interrupt here. */\r
 333 }\r
 334 /*-----------------------------------------------------------*/\r
 335 \r
 336 /*\r
 337  * Manual context switch.  The first thing we do is save the registers so we\r
 338  * can use a naked attribute.\r
 339  */\r
 340 void vPortYield( void ) __attribute__ ( ( naked ) );\r
 341 void vPortYield( void )\r
 342 {\r
 343         portSAVE_CONTEXT();\r
 344         vTaskSwitchContext();\r
 345         portRESTORE_CONTEXT();\r
 346 \r
 347         asm volatile ( "ret" );\r
 348 }\r
 349 /*-----------------------------------------------------------*/\r
 350 \r
 351 /*\r
 352  * Context switch function used by the tick.  This must be identical to \r
 353  * vPortYield() from the call to vTaskSwitchContext() onwards.  The only\r
 354  * difference from vPortYield() is the tick count is incremented as the\r
 355  * call comes from the tick ISR.\r
 356  */\r
 357 void vPortYieldFromTick( void ) __attribute__ ( ( naked ) );\r
 358 void vPortYieldFromTick( void )\r
 359 {\r
 360         portSAVE_CONTEXT();\r
 361         vTaskIncrementTick();\r
 362         vTaskSwitchContext();\r
 363         portRESTORE_CONTEXT();\r
 364 \r
 365         asm volatile ( "ret" );\r
 366 }\r
 367 /*-----------------------------------------------------------*/\r
 368 \r
 369 /*\r
 370  * Setup timer 1 compare match A to generate a tick interrupt.\r
 371  */\r
 372 static void prvSetupTimerInterrupt( void )\r
 373 {\r
 374 unsigned portLONG ulCompareMatch;\r
 375 unsigned portCHAR ucHighByte, ucLowByte;\r
 376 \r
 377         /* Using 16bit timer 1 to generate the tick.  Correct fuses must be\r
 378         selected for the configCPU_CLOCK_HZ clock. */\r
 379 \r
 380         ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;\r
 381 \r
 382         /* We only have 16 bits so have to scale to get our required tick rate. */\r
 383         ulCompareMatch /= portCLOCK_PRESCALER;\r
 384 \r
 385         /* Adjust for correct value. */\r
 386         ulCompareMatch -= ( unsigned portLONG ) 1;\r
 387 \r
 388         /* Setup compare match value for compare match A.  Interrupts are disabled \r
 389         before this is called so we need not worry here. */\r
 390         ucLowByte = ( unsigned portCHAR ) ( ulCompareMatch & ( unsigned portLONG ) 0xff );\r
 391         ulCompareMatch >>= 8;\r
 392         ucHighByte = ( unsigned portCHAR ) ( ulCompareMatch & ( unsigned portLONG ) 0xff );\r
 393         OCR1AH = ucHighByte;\r
 394         OCR1AL = ucLowByte;\r
 395 \r
 396         /* Setup clock source and compare match behaviour. */\r
 397         ucLowByte = portCLEAR_COUNTER_ON_MATCH | portPRESCALE_64;\r
 398         TCCR1B = ucLowByte;\r
 399 \r
 400         /* Enable the interrupt - this is okay as interrupt are currently globally\r
 401         disabled. */\r
 402         ucLowByte = TIMSK;\r
 403         ucLowByte |= portCOMPARE_MATCH_A_INTERRUPT_ENABLE;\r
 404         TIMSK = ucLowByte;\r
 405 }\r
 406 /*-----------------------------------------------------------*/\r
 407 \r
 408 #if configUSE_PREEMPTION == 1\r
 409 \r
 410         /*\r
 411          * Tick ISR for preemptive scheduler.  We can use a naked attribute as\r
 412          * the context is saved at the start of vPortYieldFromTick().  The tick\r
 413          * count is incremented after the context is saved.\r
 414          */\r
 415         void SIG_OUTPUT_COMPARE1A( void ) __attribute__ ( ( signal, naked ) );\r
 416         void SIG_OUTPUT_COMPARE1A( void )\r
 417         {\r
 418                 vPortYieldFromTick();\r
 419                 asm volatile ( "reti" );\r
 420         }\r
 421 #else\r
 422 \r
 423         /*\r
 424          * Tick ISR for the cooperative scheduler.  All this does is increment the\r
 425          * tick count.  We don't need to switch context, this can only be done by\r
 426          * manual calls to taskYIELD();\r
 427          */\r
 428         void SIG_OUTPUT_COMPARE1A( void ) __attribute__ ( ( signal ) );\r
 429         void SIG_OUTPUT_COMPARE1A( void )\r
 430         {\r
 431                 vTaskIncrementTick();\r
 432         }\r
 433 #endif\r
 434 \r
 435 \r
 436         \r