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

   1 /*
   2  * FreeRTOS Kernel <DEVELOPMENT BRANCH>
   3  * Copyright (C) 2021 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
   4  *
   5  * SPDX-License-Identifier: MIT
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a copy of
   8  * this software and associated documentation files (the "Software"), to deal in
   9  * the Software without restriction, including without limitation the rights to
  10  * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
  11  * the Software, and to permit persons to whom the Software is furnished to do so,
  12  * subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included in all
  15  * copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
  19  * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
  20  * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
  21  * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  22  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  23  *
  24  * https://www.FreeRTOS.org
  25  * https://github.com/FreeRTOS
  26  *
  27  */
  28
  29 #include <stdlib.h>
  30
  31 #include <avr/interrupt.h>
  32 #include "porthardware.h"
  33 #include "FreeRTOS.h"
  34 #include "task.h"
  35
  36 /*-----------------------------------------------------------
  37 * Implementation of functions defined in portable.h for the AVR port.
  38 *----------------------------------------------------------*/
  39
  40 /* Start tasks with interrupts enables. */
  41 #define portFLAGS_INT_ENABLED    ( ( StackType_t ) 0x80 )
  42
  43 /*-----------------------------------------------------------*/
  44
  45 /* We require the address of the pxCurrentTCB variable, but don't want to know
  46  * any details of its type. */
  47 typedef void RTOS_TCB_t;
  48 extern volatile RTOS_TCB_t * volatile pxCurrentTCB;
  49
  50 /*-----------------------------------------------------------*/
  51
  52 /*
  53  * Macro to save all the general purpose registers, the save the stack pointer
  54  * into the TCB.
  55  *
  56  * The first thing we do is save the flags then disable interrupts.  This is to
  57  * guard our stack against having a context switch interrupt after we have already
  58  * pushed the registers onto the stack - causing the 32 registers to be on the
  59  * stack twice.
  60  *
  61  * r1 is set to zero as the compiler expects it to be thus, however some
  62  * of the math routines make use of R1.
  63  *
  64  * The interrupts will have been disabled during the call to portSAVE_CONTEXT()
  65  * so we need not worry about reading/writing to the stack pointer.
  66  */
  67
  68 #define portSAVE_CONTEXT()                              \
  69     asm volatile ( "push  r0                      \n\t" \
  70                    "in    r0, __SREG__            \n\t" \
  71                    "cli                           \n\t" \
  72                    "push  r0                      \n\t" \
  73                    "push  r1                      \n\t" \
  74                    "clr   r1                      \n\t" \
  75                    "push  r2                      \n\t" \
  76                    "push  r3                      \n\t" \
  77                    "push  r4                      \n\t" \
  78                    "push  r5                      \n\t" \
  79                    "push  r6                      \n\t" \
  80                    "push  r7                      \n\t" \
  81                    "push  r8                      \n\t" \
  82                    "push  r9                      \n\t" \
  83                    "push  r10                     \n\t" \
  84                    "push  r11                     \n\t" \
  85                    "push  r12                     \n\t" \
  86                    "push  r13                     \n\t" \
  87                    "push  r14                     \n\t" \
  88                    "push  r15                     \n\t" \
  89                    "push  r16                     \n\t" \
  90                    "push  r17                     \n\t" \
  91                    "push  r18                     \n\t" \
  92                    "push  r19                     \n\t" \
  93                    "push  r20                     \n\t" \
  94                    "push  r21                     \n\t" \
  95                    "push  r22                     \n\t" \
  96                    "push  r23                     \n\t" \
  97                    "push  r24                     \n\t" \
  98                    "push  r25                     \n\t" \
  99                    "push  r26                     \n\t" \
 100                    "push  r27                     \n\t" \
 101                    "push  r28                     \n\t" \
 102                    "push  r29                     \n\t" \
 103                    "push  r30                     \n\t" \
 104                    "push  r31                     \n\t" \
 105                    "lds   r26, pxCurrentTCB       \n\t" \
 106                    "lds   r27, pxCurrentTCB + 1   \n\t" \
 107                    "in    r0, __SP_L__            \n\t" \
 108                    "st    x+, r0                  \n\t" \
 109                    "in    r0, __SP_H__            \n\t" \
 110                    "st    x+, r0                  \n\t" );
 111
 112 /*
 113  * Opposite to portSAVE_CONTEXT().  Interrupts will have been disabled during
 114  * the context save so we can write to the stack pointer.
 115  */
 116
 117 #define portRESTORE_CONTEXT()                           \
 118     asm volatile ( "lds   r26, pxCurrentTCB       \n\t" \
 119                    "lds   r27, pxCurrentTCB + 1   \n\t" \
 120                    "ld    r28, x+                 \n\t" \
 121                    "out   __SP_L__, r28           \n\t" \
 122                    "ld    r29, x+                 \n\t" \
 123                    "out   __SP_H__, r29           \n\t" \
 124                    "pop   r31                     \n\t" \
 125                    "pop   r30                     \n\t" \
 126                    "pop   r29                     \n\t" \
 127                    "pop   r28                     \n\t" \
 128                    "pop   r27                     \n\t" \
 129                    "pop   r26                     \n\t" \
 130                    "pop   r25                     \n\t" \
 131                    "pop   r24                     \n\t" \
 132                    "pop   r23                     \n\t" \
 133                    "pop   r22                     \n\t" \
 134                    "pop   r21                     \n\t" \
 135                    "pop   r20                     \n\t" \
 136                    "pop   r19                     \n\t" \
 137                    "pop   r18                     \n\t" \
 138                    "pop   r17                     \n\t" \
 139                    "pop   r16                     \n\t" \
 140                    "pop   r15                     \n\t" \
 141                    "pop   r14                     \n\t" \
 142                    "pop   r13                     \n\t" \
 143                    "pop   r12                     \n\t" \
 144                    "pop   r11                     \n\t" \
 145                    "pop   r10                     \n\t" \
 146                    "pop   r9                      \n\t" \
 147                    "pop   r8                      \n\t" \
 148                    "pop   r7                      \n\t" \
 149                    "pop   r6                      \n\t" \
 150                    "pop   r5                      \n\t" \
 151                    "pop   r4                      \n\t" \
 152                    "pop   r3                      \n\t" \
 153                    "pop   r2                      \n\t" \
 154                    "pop   r1                      \n\t" \
 155                    "pop   r0                      \n\t" \
 156                    "out   __SREG__, r0            \n\t" \
 157                    "pop   r0                      \n\t" );
 158
 159 /*-----------------------------------------------------------*/
 160
 161 /*
 162  * Perform hardware setup to enable ticks from timer.
 163  */
 164 static void prvSetupTimerInterrupt( void );
 165 /*-----------------------------------------------------------*/
 166
 167 /*
 168  * See header file for description.
 169  */
 170 StackType_t * pxPortInitialiseStack( StackType_t * pxTopOfStack,
 171                                      TaskFunction_t pxCode,
 172                                      void * pvParameters )
 173 {
 174     uint16_t usAddress;
 175
 176     /*lint -e950 -e611 -e923 Lint doesn't like this much - but nothing I can do about it. */
 177
 178     /* Place a few bytes of known values on the bottom of the stack.
 179      * This is just useful for debugging. Uncomment if needed. */
 180     /* *pxTopOfStack = 0x11; */
 181     /* pxTopOfStack--; */
 182     /* *pxTopOfStack = 0x22; */
 183     /* pxTopOfStack--; */
 184     /* *pxTopOfStack = 0x33; */
 185     /* pxTopOfStack--; */
 186
 187     /* The start of the task code will be popped off the stack last, so place
 188      * it on first. */
 189     usAddress = ( uint16_t ) pxCode;
 190     *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
 191     pxTopOfStack--;
 192
 193     usAddress >>= 8;
 194     *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
 195     pxTopOfStack--;
 196
 197     /* Next simulate the stack as if after a call to portSAVE_CONTEXT().
 198     *  portSAVE_CONTEXT places the flags on the stack immediately after r0
 199     *  to ensure the interrupts get disabled as soon as possible, and so ensuring
 200     *  the stack use is minimal should a context switch interrupt occur. */
 201     *pxTopOfStack = ( StackType_t ) 0x00; /* R0 */
 202     pxTopOfStack--;
 203     *pxTopOfStack = portFLAGS_INT_ENABLED;
 204     pxTopOfStack--;
 205
 206     /* Now the remaining registers.   The compiler expects R1 to be 0. */
 207     *pxTopOfStack = ( StackType_t ) 0x00; /* R1 */
 208
 209     /* Leave R2 - R23 untouched */
 210     pxTopOfStack -= 23;
 211
 212     /* Place the parameter on the stack in the expected location. */
 213     usAddress = ( uint16_t ) pvParameters;
 214     *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
 215     pxTopOfStack--;
 216
 217     usAddress >>= 8;
 218     *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
 219
 220     /* Leave register R26 - R31 untouched */
 221     pxTopOfStack -= 7;
 222
 223     /*lint +e950 +e611 +e923 */
 224
 225     return pxTopOfStack;
 226 }
 227 /*-----------------------------------------------------------*/
 228
 229 BaseType_t xPortStartScheduler( void )
 230 {
 231     /* Setup the hardware to generate the tick. */
 232     prvSetupTimerInterrupt();
 233
 234     /* Restore the context of the first task that is going to run. */
 235     portRESTORE_CONTEXT();
 236
 237     /* Simulate a function call end as generated by the compiler.  We will now
 238      * jump to the start of the task the context of which we have just restored. */
 239     asm volatile ( "ret" );
 240
 241     /* Should not get here. */
 242     return pdTRUE;
 243 }
 244 /*-----------------------------------------------------------*/
 245
 246 void vPortEndScheduler( void )
 247 {
 248     /* vPortEndScheduler is not implemented in this port. */
 249 }
 250 /*-----------------------------------------------------------*/
 251
 252 /*
 253  * Manual context switch.  The first thing we do is save the registers so we
 254  * can use a naked attribute.
 255  */
 256 void vPortYield( void ) __attribute__( ( naked ) );
 257 void vPortYield( void )
 258 {
 259     portSAVE_CONTEXT();
 260     vTaskSwitchContext();
 261     portRESTORE_CONTEXT();
 262     asm volatile ( "ret" );
 263 }
 264 /*-----------------------------------------------------------*/
 265
 266 /*
 267  * Manual context switch callable from ISRs. The first thing
 268  * we do is save the registers so we can use a naked attribute.
 269  */
 270 void vPortYieldFromISR( void ) __attribute__( ( naked ) );
 271 void vPortYieldFromISR( void )
 272 {
 273     portSAVE_CONTEXT();
 274     vTaskSwitchContext();
 275     portRESTORE_CONTEXT();
 276     asm volatile ( "reti" );
 277 }
 278 /*-----------------------------------------------------------*/
 279
 280 /*
 281  * Context switch function used by the tick.  This must be identical to
 282  * vPortYield() from the call to vTaskSwitchContext() onwards.  The only
 283  * difference from vPortYield() is the tick count is incremented as the
 284  * call comes from the tick ISR.
 285  */
 286 void vPortYieldFromTick( void ) __attribute__( ( naked ) );
 287 void vPortYieldFromTick( void )
 288 {
 289     portSAVE_CONTEXT();
 290
 291     if( xTaskIncrementTick() != pdFALSE )
 292     {
 293         vTaskSwitchContext();
 294     }
 295
 296     portRESTORE_CONTEXT();
 297
 298     asm volatile ( "reti" );
 299 }
 300 /*-----------------------------------------------------------*/
 301
 302 /*
 303  * Setup timer to generate a tick interrupt.
 304  */
 305 static void prvSetupTimerInterrupt( void )
 306 {
 307     TICK_init();
 308 }
 309 /*-----------------------------------------------------------*/
 310
 311 #if configUSE_PREEMPTION == 1
 312
 313 /*
 314  * Tick ISR for preemptive scheduler.  We can use a naked attribute as
 315  * the context is saved at the start of vPortYieldFromTick().  The tick
 316  * count is incremented after the context is saved.
 317  */
 318     ISR( TICK_INT_vect, ISR_NAKED )
 319     {
 320         /* Clear tick interrupt flag. */
 321         CLR_INT( INT_FLAGS, INT_MASK );
 322
 323         vPortYieldFromTick();
 324
 325         asm volatile ( "reti" );
 326     }
 327 #else  /* if configUSE_PREEMPTION == 1 */
 328
 329 /*
 330  * Tick ISR for the cooperative scheduler.  All this does is increment the
 331  * tick count.  We don't need to switch context, this can only be done by
 332  * manual calls to taskYIELD();
 333  */
 334     ISR( TICK_INT_vect )
 335     {
 336         /* Clear tick interrupt flag. */
 337         INT_FLAGS = INT_MASK;
 338         xTaskIncrementTick();
 339     }
 340 #endif /* if configUSE_PREEMPTION == 1 */