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port.c
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/* Author: Kurnia D Win
* This is port of AVR XMega for freeRTOS V8.1.2
*
* Note:
* Using TCC0 timer
* Assuming RAMPD, RAMPX, RAMPY, RAMPZ, and EIND are not part of execution-context
*/
#include <avr/io.h>
#include <avr/interrupt.h>
#include "FreeRTOS.h"
#include "task.h"
/*-----------------------------------------------------------
* Implementation of functions defined in portable.h for the AVR XMEGA port.
*----------------------------------------------------------*/
/* Start tasks with interrupts enables. */
#define portFLAGS_INT_ENABLED ( ( StackType_t ) 0x80 )
/*-----------------------------------------------------------*/
/* We require the address of the pxCurrentTCB variable, but don't want to know
any details of its type. */
typedef void TCB_t;
extern volatile TCB_t * volatile pxCurrentTCB;
/*-----------------------------------------------------------*/
/*
* Macro to save all the general purpose registers, the save the stack pointer
* into the TCB.
*
* The first thing we do is save the flags then disable interrupts. This is to
* guard our stack against having a context switch interrupt after we have already
* pushed the registers onto the stack - causing the 32 registers to be on the
* stack twice.
*
* r1 is set to zero as the compiler expects it to be thus, however some
* of the math routines make use of R1.
*
* The interrupts will have been disabled during the call to portSAVE_CONTEXT()
* so we need not worry about reading/writing to the stack pointer.
*/
#define portSAVE_CONTEXT() \
asm volatile ( "push r0 \n\t" \
"in r0, __SREG__ \n\t" \
"cli \n\t" \
"push r0 \n\t" \
"push r1 \n\t" \
"clr r1 \n\t" \
"push r2 \n\t" \
"push r3 \n\t" \
"push r4 \n\t" \
"push r5 \n\t" \
"push r6 \n\t" \
"push r7 \n\t" \
"push r8 \n\t" \
"push r9 \n\t" \
"push r10 \n\t" \
"push r11 \n\t" \
"push r12 \n\t" \
"push r13 \n\t" \
"push r14 \n\t" \
"push r15 \n\t" \
"push r16 \n\t" \
"push r17 \n\t" \
"push r18 \n\t" \
"push r19 \n\t" \
"push r20 \n\t" \
"push r21 \n\t" \
"push r22 \n\t" \
"push r23 \n\t" \
"push r24 \n\t" \
"push r25 \n\t" \
"push r26 \n\t" \
"push r27 \n\t" \
"push r28 \n\t" \
"push r29 \n\t" \
"push r30 \n\t" \
"push r31 \n\t" \
"lds r26, pxCurrentTCB \n\t" \
"lds r27, pxCurrentTCB + 1 \n\t" \
"in r0, __SP_L__ \n\t" \
"st x+, r0 \n\t" \
"in r0, __SP_H__ \n\t" \
"st x+, r0 \n\t" \
);
/*
* Opposite to portSAVE_CONTEXT(). Interrupts will have been disabled during
* the context save so we can write to the stack pointer.
*/
#define portRESTORE_CONTEXT() \
asm volatile ( "lds r26, pxCurrentTCB \n\t" \
"lds r27, pxCurrentTCB + 1 \n\t" \
"ld r0, x+ \n\t" \
"out __SP_L__, r0 \n\t" \
"ld r0, x+ \n\t" \
"out __SP_H__, r0 \n\t" \
"pop r31 \n\t" \
"pop r30 \n\t" \
"pop r29 \n\t" \
"pop r28 \n\t" \
"pop r27 \n\t" \
"pop r26 \n\t" \
"pop r25 \n\t" \
"pop r24 \n\t" \
"pop r23 \n\t" \
"pop r22 \n\t" \
"pop r21 \n\t" \
"pop r20 \n\t" \
"pop r19 \n\t" \
"pop r18 \n\t" \
"pop r17 \n\t" \
"pop r16 \n\t" \
"pop r15 \n\t" \
"pop r14 \n\t" \
"pop r13 \n\t" \
"pop r12 \n\t" \
"pop r11 \n\t" \
"pop r10 \n\t" \
"pop r9 \n\t" \
"pop r8 \n\t" \
"pop r7 \n\t" \
"pop r6 \n\t" \
"pop r5 \n\t" \
"pop r4 \n\t" \
"pop r3 \n\t" \
"pop r2 \n\t" \
"pop r1 \n\t" \
"pop r0 \n\t" \
"out __SREG__, r0 \n\t" \
"pop r0 \n\t" \
);
/*-----------------------------------------------------------*/
/*
* Perform hardware setup to enable ticks from TCC0.
*/
static void prvSetupTimerInterrupt( void );
/*-----------------------------------------------------------*/
/*
* See header file for description.
*/
StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
{
uint32_t ulAddress;
uint16_t usAddress;
/* Place a few bytes of known values on the bottom of the stack.
This is just useful for debugging. */
*pxTopOfStack = 0x11;
pxTopOfStack--;
*pxTopOfStack = 0x22;
pxTopOfStack--;
*pxTopOfStack = 0x33;
pxTopOfStack--;
/* Simulate how the stack would look after a call to vPortYield() generated by
the compiler. */
/*lint -e950 -e611 -e923 Lint doesn't like this much - but nothing I can do about it. */
/* The start of the task code will be popped off the stack last, so place
it on first. */
ulAddress = ( uint32_t ) pxCode;
*pxTopOfStack = ( StackType_t ) ( ulAddress & ( uint32_t ) 0x000000ff );
pxTopOfStack--;
ulAddress >>= 8;
*pxTopOfStack = ( StackType_t ) ( ulAddress & ( uint32_t ) 0x000000ff );
pxTopOfStack--;
#ifdef __AVR_3_BYTE_PC__
ulAddress >>= 8;
*pxTopOfStack = ( StackType_t ) ( ulAddress & ( uint32_t ) 0x000000ff );
pxTopOfStack--;
#endif
/* Next simulate the stack as if after a call to portSAVE_CONTEXT().
portSAVE_CONTEXT places the flags on the stack immediately after r0
to ensure the interrupts get disabled as soon as possible, and so ensuring
the stack use is minimal should a context switch interrupt occur. */
*pxTopOfStack = ( StackType_t ) 0x00; /* R0 */
pxTopOfStack--;
*pxTopOfStack = portFLAGS_INT_ENABLED;
pxTopOfStack--;
/* Now the remaining registers. The compiler expects R1 to be 0. */
*pxTopOfStack = ( StackType_t ) 0x00; /* R1 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x02; /* R2 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x03; /* R3 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x04; /* R4 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x05; /* R5 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x06; /* R6 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x07; /* R7 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x08; /* R8 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x09; /* R9 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x10; /* R10 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x11; /* R11 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x12; /* R12 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x13; /* R13 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x14; /* R14 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x15; /* R15 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x16; /* R16 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x17; /* R17 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x18; /* R18 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x19; /* R19 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x20; /* R20 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x21; /* R21 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x22; /* R22 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x23; /* R23 */
pxTopOfStack--;
/* Place the parameter on the stack in the expected location. */
usAddress = ( uint16_t ) pvParameters;
*pxTopOfStack = ( StackType_t ) ( usAddress & ( uint32_t ) 0x000000ff );
pxTopOfStack--;
usAddress >>= 8;
*pxTopOfStack = ( StackType_t ) ( usAddress & ( uint32_t ) 0x000000ff );
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x26; /* R26 X */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x27; /* R27 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x28; /* R28 Y */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x29; /* R29 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x30; /* R30 Z */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x31; /* R31 */
pxTopOfStack--;
/*lint +e950 +e611 +e923 */
return pxTopOfStack;
}
/*-----------------------------------------------------------*/
BaseType_t xPortStartScheduler( void )
{
/* Setup the hardware to generate the tick. */
prvSetupTimerInterrupt();
/* Restore the context of the first task that is going to run. */
portRESTORE_CONTEXT();
/* Simulate a function call end as generated by the compiler. We will now
jump to the start of the task the context of which we have just restored. */
asm volatile ( "ret" );
/* Should not get here. */
return pdTRUE;
}
/*-----------------------------------------------------------*/
/* not used */
// void vPortEndScheduler(void)
// {
// /* It is unlikely that the AVR port will get stopped. If required simply
// disable the tick interrupt here. */
// }
/*-----------------------------------------------------------*/
/*
* Manual context switch. The first thing we do is save the registers so we
* can use a naked attribute.
*/
void vPortYield( void ) __attribute__ ( ( naked ) );
void vPortYield( void )
{
portSAVE_CONTEXT();
vTaskSwitchContext();
portRESTORE_CONTEXT();
asm volatile ( "ret" );
}
/*-----------------------------------------------------------*/
#if configUSE_PREEMPTION == 1
/*
* Tick ISR for preemptive scheduler. We can use a naked attribute as
* the context is saved at the start of vPortYieldFromTick(). The tick
* count is incremented after the context is saved.
*/
ISR(TCC0_OVF_vect, ISR_NAKED)
{
/*
* Context switch function used by the tick. This must be identical to
* vPortYield() from the call to vTaskSwitchContext() onwards. The only
* difference from vPortYield() is the tick count is incremented as the
* call comes from the tick ISR.
*/
portSAVE_CONTEXT();
if( xTaskIncrementTick() != pdFALSE )
{
vTaskSwitchContext();
}
portRESTORE_CONTEXT();
asm volatile ( "reti" );
}
#else
/*
* Tick ISR for the cooperative scheduler. All this does is increment the
* tick count. We don't need to switch context, this can only be done by
* manual calls to taskYIELD();
*/
ISR(TCC0_OVF_vect)
{
xTaskIncrementTick();
}
#endif
/*-----------------------------------------------------------*/
/*
* Setup timer generate a tick interrupt.
*/
static void prvSetupTimerInterrupt(void)
{
// disable global interrupt for a moment
cli();
{
//enable TC0 clock source, high resolution
PR.PRPC &= ~(PR_TC0_bm | PR_HIRES_bm);
//set period of counter
TCC0.PER = (configCPU_CLOCK_HZ / configTICK_RATE_HZ / 1) - 1;
//enable interrupt and set low level
TCC0.INTCTRLA = TC_OVFINTLVL_LO_gc;
//enable low-level interrupt
PMIC.CTRL |= PMIC_LOLVLEN_bm;
//select (start) the clock source
TCC0.CTRLA = TC_CLKSEL_DIV1_gc;
}
// enable global interrupt
sei();
}