begriffs open source - freertos/blob - portable/GCC/AVR_Mega0/port.c

   1 /*
   2  * FreeRTOS Kernel V10.4.3 LTS Patch 3
   3  * Copyright (C) 2017 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
   4  *
   5  * Permission is hereby granted, free of charge, to any person obtaining a copy of
   6  * this software and associated documentation files (the "Software"), to deal in
   7  * the Software without restriction, including without limitation the rights to
   8  * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
   9  * the Software, and to permit persons to whom the Software is furnished to do so,
  10  * subject to the following conditions:
  11  *
  12  * The above copyright notice and this permission notice shall be included in all
  13  * copies or substantial portions of the Software. If you wish to use our Amazon
  14  * FreeRTOS name, please do so in a fair use way that does not cause confusion.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
  18  * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
  19  * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
  20  * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  21  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  22  *
  23  * https://www.FreeRTOS.org
  24  * https://github.com/FreeRTOS
  25  *
  26  */
  27
  28 #include <stdlib.h>
  29
  30 #include <avr/interrupt.h>
  31 #include "porthardware.h"
  32 #include "FreeRTOS.h"
  33 #include "task.h"
  34
  35 /*-----------------------------------------------------------
  36 * Implementation of functions defined in portable.h for the AVR port.
  37 *----------------------------------------------------------*/
  38
  39 /* Start tasks with interrupts enables. */
  40 #define portFLAGS_INT_ENABLED    ( ( StackType_t ) 0x80 )
  41
  42 /*-----------------------------------------------------------*/
  43
  44 /* We require the address of the pxCurrentTCB variable, but don't want to know
  45  * any details of its type. */
  46 typedef void RTOS_TCB_t;
  47 extern volatile RTOS_TCB_t * volatile pxCurrentTCB;
  48
  49 /*-----------------------------------------------------------*/
  50
  51 /*
  52  * Macro to save all the general purpose registers, the save the stack pointer
  53  * into the TCB.
  54  *
  55  * The first thing we do is save the flags then disable interrupts.  This is to
  56  * guard our stack against having a context switch interrupt after we have already
  57  * pushed the registers onto the stack - causing the 32 registers to be on the
  58  * stack twice.
  59  *
  60  * r1 is set to zero as the compiler expects it to be thus, however some
  61  * of the math routines make use of R1.
  62  *
  63  * The interrupts will have been disabled during the call to portSAVE_CONTEXT()
  64  * so we need not worry about reading/writing to the stack pointer.
  65  */
  66
  67 #define portSAVE_CONTEXT()                              \
  68     asm volatile ( "push  r0                      \n\t" \
  69                    "in    r0, __SREG__            \n\t" \
  70                    "cli                           \n\t" \
  71                    "push  r0                      \n\t" \
  72                    "push  r1                      \n\t" \
  73                    "clr   r1                      \n\t" \
  74                    "push  r2                      \n\t" \
  75                    "push  r3                      \n\t" \
  76                    "push  r4                      \n\t" \
  77                    "push  r5                      \n\t" \
  78                    "push  r6                      \n\t" \
  79                    "push  r7                      \n\t" \
  80                    "push  r8                      \n\t" \
  81                    "push  r9                      \n\t" \
  82                    "push  r10                     \n\t" \
  83                    "push  r11                     \n\t" \
  84                    "push  r12                     \n\t" \
  85                    "push  r13                     \n\t" \
  86                    "push  r14                     \n\t" \
  87                    "push  r15                     \n\t" \
  88                    "push  r16                     \n\t" \
  89                    "push  r17                     \n\t" \
  90                    "push  r18                     \n\t" \
  91                    "push  r19                     \n\t" \
  92                    "push  r20                     \n\t" \
  93                    "push  r21                     \n\t" \
  94                    "push  r22                     \n\t" \
  95                    "push  r23                     \n\t" \
  96                    "push  r24                     \n\t" \
  97                    "push  r25                     \n\t" \
  98                    "push  r26                     \n\t" \
  99                    "push  r27                     \n\t" \
 100                    "push  r28                     \n\t" \
 101                    "push  r29                     \n\t" \
 102                    "push  r30                     \n\t" \
 103                    "push  r31                     \n\t" \
 104                    "lds   r26, pxCurrentTCB       \n\t" \
 105                    "lds   r27, pxCurrentTCB + 1   \n\t" \
 106                    "in    r0, __SP_L__            \n\t" \
 107                    "st    x+, r0                  \n\t" \
 108                    "in    r0, __SP_H__            \n\t" \
 109                    "st    x+, r0                  \n\t" );
 110
 111 /*
 112  * Opposite to portSAVE_CONTEXT().  Interrupts will have been disabled during
 113  * the context save so we can write to the stack pointer.
 114  */
 115
 116 #define portRESTORE_CONTEXT()                           \
 117     asm volatile ( "lds   r26, pxCurrentTCB       \n\t" \
 118                    "lds   r27, pxCurrentTCB + 1   \n\t" \
 119                    "ld    r28, x+                 \n\t" \
 120                    "out   __SP_L__, r28           \n\t" \
 121                    "ld    r29, x+                 \n\t" \
 122                    "out   __SP_H__, r29           \n\t" \
 123                    "pop   r31                     \n\t" \
 124                    "pop   r30                     \n\t" \
 125                    "pop   r29                     \n\t" \
 126                    "pop   r28                     \n\t" \
 127                    "pop   r27                     \n\t" \
 128                    "pop   r26                     \n\t" \
 129                    "pop   r25                     \n\t" \
 130                    "pop   r24                     \n\t" \
 131                    "pop   r23                     \n\t" \
 132                    "pop   r22                     \n\t" \
 133                    "pop   r21                     \n\t" \
 134                    "pop   r20                     \n\t" \
 135                    "pop   r19                     \n\t" \
 136                    "pop   r18                     \n\t" \
 137                    "pop   r17                     \n\t" \
 138                    "pop   r16                     \n\t" \
 139                    "pop   r15                     \n\t" \
 140                    "pop   r14                     \n\t" \
 141                    "pop   r13                     \n\t" \
 142                    "pop   r12                     \n\t" \
 143                    "pop   r11                     \n\t" \
 144                    "pop   r10                     \n\t" \
 145                    "pop   r9                      \n\t" \
 146                    "pop   r8                      \n\t" \
 147                    "pop   r7                      \n\t" \
 148                    "pop   r6                      \n\t" \
 149                    "pop   r5                      \n\t" \
 150                    "pop   r4                      \n\t" \
 151                    "pop   r3                      \n\t" \
 152                    "pop   r2                      \n\t" \
 153                    "pop   r1                      \n\t" \
 154                    "pop   r0                      \n\t" \
 155                    "out   __SREG__, r0            \n\t" \
 156                    "pop   r0                      \n\t" );
 157
 158 /*-----------------------------------------------------------*/
 159
 160 /*
 161  * Perform hardware setup to enable ticks from timer.
 162  */
 163 static void prvSetupTimerInterrupt( void );
 164 /*-----------------------------------------------------------*/
 165
 166 /*
 167  * See header file for description.
 168  */
 169 StackType_t * pxPortInitialiseStack( StackType_t * pxTopOfStack,
 170                                      TaskFunction_t pxCode,
 171                                      void * pvParameters )
 172 {
 173     uint16_t usAddress;
 174
 175     /*lint -e950 -e611 -e923 Lint doesn't like this much - but nothing I can do about it. */
 176
 177     /* Place a few bytes of known values on the bottom of the stack.
 178      * This is just useful for debugging. Uncomment if needed. */
 179     /* *pxTopOfStack = 0x11; */
 180     /* pxTopOfStack--; */
 181     /* *pxTopOfStack = 0x22; */
 182     /* pxTopOfStack--; */
 183     /* *pxTopOfStack = 0x33; */
 184     /* pxTopOfStack--; */
 185
 186     /* The start of the task code will be popped off the stack last, so place
 187      * it on first. */
 188     usAddress = ( uint16_t ) pxCode;
 189     *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
 190     pxTopOfStack--;
 191
 192     usAddress >>= 8;
 193     *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
 194     pxTopOfStack--;
 195
 196     /* Next simulate the stack as if after a call to portSAVE_CONTEXT().
 197     *  portSAVE_CONTEXT places the flags on the stack immediately after r0
 198     *  to ensure the interrupts get disabled as soon as possible, and so ensuring
 199     *  the stack use is minimal should a context switch interrupt occur. */
 200     *pxTopOfStack = ( StackType_t ) 0x00; /* R0 */
 201     pxTopOfStack--;
 202     *pxTopOfStack = portFLAGS_INT_ENABLED;
 203     pxTopOfStack--;
 204
 205     /* Now the remaining registers.   The compiler expects R1 to be 0. */
 206     *pxTopOfStack = ( StackType_t ) 0x00; /* R1 */
 207
 208     /* Leave R2 - R23 untouched */
 209     pxTopOfStack -= 23;
 210
 211     /* Place the parameter on the stack in the expected location. */
 212     usAddress = ( uint16_t ) pvParameters;
 213     *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
 214     pxTopOfStack--;
 215
 216     usAddress >>= 8;
 217     *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
 218
 219     /* Leave register R26 - R31 untouched */
 220     pxTopOfStack -= 7;
 221
 222     /*lint +e950 +e611 +e923 */
 223
 224     return pxTopOfStack;
 225 }
 226 /*-----------------------------------------------------------*/
 227
 228 BaseType_t xPortStartScheduler( void )
 229 {
 230     /* Setup the hardware to generate the tick. */
 231     prvSetupTimerInterrupt();
 232
 233     /* Restore the context of the first task that is going to run. */
 234     portRESTORE_CONTEXT();
 235
 236     /* Simulate a function call end as generated by the compiler.  We will now
 237      * jump to the start of the task the context of which we have just restored. */
 238     asm volatile ( "ret" );
 239
 240     /* Should not get here. */
 241     return pdTRUE;
 242 }
 243 /*-----------------------------------------------------------*/
 244
 245 void vPortEndScheduler( void )
 246 {
 247     /* vPortEndScheduler is not implemented in this port. */
 248 }
 249 /*-----------------------------------------------------------*/
 250
 251 /*
 252  * Manual context switch.  The first thing we do is save the registers so we
 253  * can use a naked attribute.
 254  */
 255 void vPortYield( void ) __attribute__( ( naked ) );
 256 void vPortYield( void )
 257 {
 258     portSAVE_CONTEXT();
 259     vTaskSwitchContext();
 260     portRESTORE_CONTEXT();
 261     asm volatile ( "ret" );
 262 }
 263 /*-----------------------------------------------------------*/
 264
 265 /*
 266  * Manual context switch callable from ISRs. The first thing
 267  * we do is save the registers so we can use a naked attribute.
 268  */
 269 void vPortYieldFromISR( void ) __attribute__( ( naked ) );
 270 void vPortYieldFromISR( void )
 271 {
 272     portSAVE_CONTEXT();
 273     vTaskSwitchContext();
 274     portRESTORE_CONTEXT();
 275     asm volatile ( "reti" );
 276 }
 277 /*-----------------------------------------------------------*/
 278
 279 /*
 280  * Context switch function used by the tick.  This must be identical to
 281  * vPortYield() from the call to vTaskSwitchContext() onwards.  The only
 282  * difference from vPortYield() is the tick count is incremented as the
 283  * call comes from the tick ISR.
 284  */
 285 void vPortYieldFromTick( void ) __attribute__( ( naked ) );
 286 void vPortYieldFromTick( void )
 287 {
 288     portSAVE_CONTEXT();
 289
 290     if( xTaskIncrementTick() != pdFALSE )
 291     {
 292         vTaskSwitchContext();
 293     }
 294
 295     portRESTORE_CONTEXT();
 296
 297     asm volatile ( "reti" );
 298 }
 299 /*-----------------------------------------------------------*/
 300
 301 /*
 302  * Setup timer to generate a tick interrupt.
 303  */
 304 static void prvSetupTimerInterrupt( void )
 305 {
 306     TICK_init();
 307 }
 308 /*-----------------------------------------------------------*/
 309
 310 #if configUSE_PREEMPTION == 1
 311
 312 /*
 313  * Tick ISR for preemptive scheduler.  We can use a naked attribute as
 314  * the context is saved at the start of vPortYieldFromTick().  The tick
 315  * count is incremented after the context is saved.
 316  */
 317     ISR( TICK_INT_vect, ISR_NAKED )
 318     {
 319         /* Clear tick interrupt flag. */
 320         CLR_INT( INT_FLAGS, INT_MASK );
 321
 322         vPortYieldFromTick();
 323
 324         asm volatile ( "reti" );
 325     }
 326 #else  /* if configUSE_PREEMPTION == 1 */
 327
 328 /*
 329  * Tick ISR for the cooperative scheduler.  All this does is increment the
 330  * tick count.  We don't need to switch context, this can only be done by
 331  * manual calls to taskYIELD();
 332  */
 333     ISR( TICK_INT_vect )
 334     {
 335         /* Clear tick interrupt flag. */
 336         INT_FLAGS = INT_MASK;
 337         xTaskIncrementTick();
 338     }
 339 #endif /* if configUSE_PREEMPTION == 1 */