risc-v-tlm/tests/FreeRTOS/port.c

/*
    FreeRTOS V8.2.3 - Copyright (C) 2015 Real Time Engineers Ltd.
    All rights reserved

    VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.

    This file is part of the FreeRTOS distribution and was contributed
    to the project by Technolution B.V. (www.technolution.nl,
    freertos-riscv@technolution.eu) under the terms of the FreeRTOS
    contributors license.

    FreeRTOS is free software; you can redistribute it and/or modify it under
    the terms of the GNU General Public License (version 2) as published by the
    Free Software Foundation >>>> AND MODIFIED BY <<<< the FreeRTOS exception.

    ***************************************************************************
    >>!   NOTE: The modification to the GPL is included to allow you to     !<<
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    >>!   outside of the FreeRTOS kernel.                                   !<<
    ***************************************************************************

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    ***************************************************************************
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*/

/*-----------------------------------------------------------
 * Implementation of functions defined in portable.h for the RISC-V port.
 *----------------------------------------------------------*/

/* Scheduler includes. */
#include "FreeRTOS.h"
#include "task.h"
#include "portmacro.h"
#include <stdio.h>

#define TIMER (*(uint64_t *)0x40004000)
#define TIMER_CMP (*(uint64_t *)0x40004008)
#define TRACE (*(unsigned char *)0x40000000)


/* A variable is used to keep track of the critical section nesting.  This
variable has to be stored as part of the task context and must be initialised to
a non zero value to ensure interrupts don't inadvertently become unmasked before
the scheduler starts.  As it is stored as part of the task context it will
automatically be set to 0 when the first task is started. */
static UBaseType_t uxCriticalNesting = 0xaaaaaaaa;

/* Contains context when starting scheduler, save all 31 registers */
#ifdef __gracefulExit
BaseType_t xStartContext[31] = {0};
#endif

/*
 * Handler for timer interrupt
 */
void vPortSysTickHandler( void );

/*
 * Setup the timer to generate the tick interrupts.
 */
void vPortSetupTimer( void );

/*
 * Set the next interval for the timer
 */
static void prvSetNextTimerInterrupt( void );

/*
 * Used to catch tasks that attempt to return from their implementing function.
 */
static void prvTaskExitError( void );


int _write(int file, const char *ptr, int len) {
  int x;

  for (x = 0; x < len; x++) {
    TRACE =  *ptr++;
  }

  return (len);
}

int _read(int file, char* ptr, int len) {

}

int _close(int fd){

}

int _fstat_r(int fd) {

}

int _lseek_r(struct _reent *ptr, FILE *fp, long offset, int whence){

}

int _isatty_r(struct _reent *ptr, int fd) {

}

void register_timer_isr() {
  printf("Registering ISR\n");
  asm volatile("la t0, TIMER_CMP_INT \n csrw mtvec, t0");
  asm volatile("li t1, 0x888 \n csrw mie, t1");
}


/*-----------------------------------------------------------*/

/* Sets the next timer interrupt
 * Reads previous timer compare register, and adds tickrate */
static void prvSetNextTimerInterrupt(void)
{
#if 0
	__asm volatile("csrr t0,mtimecmp");
	__asm volatile("add t0,t0,%0" :: "r"(configTICK_CLOCK_HZ / configTICK_RATE_HZ));
	__asm volatile("csrw mtimecmp,t0");
#endif
	volatile uint32_t timer_value;
	timer_value = TIMER;
// 	timer_value += configTICK_CLOCK_HZ / configTICK_RATE_HZ;
	timer_value += 10000 - 620;    // timer set to 100 Hz and corrected
	TIMER_CMP = timer_value;
  // printf("ISR\n");
}
/*-----------------------------------------------------------*/

/* Sets and enable the timer interrupt */
void vPortSetupTimer(void)
{

#if 0
	__asm volatile("csrr t0,mtime");
	__asm volatile("add t0,t0,%0"::"r"(configTICK_CLOCK_HZ / configTICK_RATE_HZ));
	__asm volatile("csrw mtimecmp,t0");

	/* Enable timer interupt */
	__asm volatile("csrs mie,%0"::"r"(0x80));
#endif

        volatile uint32_t timer_value;
        
        register_timer_isr();
        
        timer_value = TIMER;
        // timer_value += configTICK_CLOCK_HZ / configTICK_RATE_HZ;
	timer_value += 10000 - 620;        // timer set to 100 Hz and corrected
        TIMER_CMP = timer_value;
}
/*-----------------------------------------------------------*/

void prvTaskExitError( void )
{
	/* A function that implements a task must not exit or attempt to return to
	its caller as there is nothing to return to.  If a task wants to exit it
	should instead call vTaskDelete( NULL ).

	Artificially force an assert() to be triggered if configASSERT() is
	defined, then stop here so application writers can catch the error. */
	configASSERT( uxCriticalNesting == ~0UL );
	portDISABLE_INTERRUPTS();
	for( ;; );
}
/*-----------------------------------------------------------*/

/* Clear current interrupt mask and set given mask */
void vPortClearInterruptMask(int mask)
{
	__asm volatile("csrw mie, %0"::"r"(mask));
}
/*-----------------------------------------------------------*/

/* Set interrupt mask and return current interrupt enable register */
int vPortSetInterruptMask(void)
{
	int ret;
	__asm volatile("csrr %0,mie":"=r"(ret));
	__asm volatile("csrc mie,%0"::"i"(7));
	return ret;
}
/*-----------------------------------------------------------*/


/*
 * See header file for description.
 */
StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
{
	/* Simulate the stack frame as it would be created by a context switch
	interrupt. */
	register int *tp asm("x3");
	pxTopOfStack--;
	*pxTopOfStack = (portSTACK_TYPE)pxCode;			/* Start address */
	pxTopOfStack -= 22;
	*pxTopOfStack = (portSTACK_TYPE)pvParameters;	/* Register a0 */
	pxTopOfStack -= 6;
	*pxTopOfStack = (portSTACK_TYPE)tp; /* Register thread pointer */
	pxTopOfStack -= 3;
	*pxTopOfStack = (portSTACK_TYPE)prvTaskExitError; /* Register ra */

	return pxTopOfStack;
}
/*-----------------------------------------------------------*/

void vPortSysTickHandler( void )
{
	prvSetNextTimerInterrupt();

	/* Increment the RTOS tick. */
	if( xTaskIncrementTick() != pdFALSE )
	{
		vTaskSwitchContext();
	}
}
/*-----------------------------------------------------------*/