/*!
\brief C part of the SVC exception handler
SVC 0 is initializing the OS and starting the scheduler.
Each thread stack frame is initialized.
\param svc_args Used to extract the SVC number
*/
void SVC_Handler_C(unsigned int * svc_args)
{
uint8_t svc_number;
svc_number = ((char *) svc_args[6])[-2]; // Memory[(Stacked PC)-2]
// marking kernel as busy
kernel_busy = 1;
switch(svc_number) {
//************* SVC( 0 ) OS Start
case (0): // OS start
// Starting the task scheduler
//TWP playing a trick here!? by making curr = next, will make next's stack and current's stack the same stack!
// will save (garbage) current register values, and then immediately restore them as next's initial values :-)
curr_task = rtr_q_h; // Switch to head ready-to-run task (Current task)
// when current task was put in RTRQ its state was set to RUNNING
svc_exc_return = HW32_REG(( curr_task->stack_p )); // Return to thread with PSP
__set_PSP(( (uint32_t) curr_task->stack_p + 10*4)); // Set PSP to @R0 of task 0 exception stack frame
NVIC_SetPriority(PendSV_IRQn, 0xFF); // Set PendSV to lowest possible priority
if (SysTick_Config(os_sysTickTicks) != 0) // 1000 Hz SysTick interrupt on 16MHz core clock
{
stop_cpu2;
// Impossible SysTick_Config number of ticks
}
__set_CONTROL(0x3); // Switch to use Process Stack, unprivileged state
__ISB(); // Execute ISB after changing CONTROL (architectural recommendation)
break;
//************* SVC( 1 ) Thread Yield
case (1): // Thread Yield
if (curr_task != rtr_q_h)
{
// Context switching needed
ScheduleContextSwitch();
}
__ISB();
break;
//************* SVC( 2 ) Stack Frame Allocation for First Launch
//TWPV6: no longer used! Functionality moved to osThreadCreate ... case left here (for now)
case (2): // Stack Allocation
__ISB();
break;
default:
#if ((ENABLE_KERNEL_PRINTF) && (ENABLE_KERNEL_PRINTF == 1))
printf("ERROR: Unknown SVC service number\n\r");
printf("- SVC number 0x%x\n\r", svc_number);
#endif
stop_cpu2;
break;
} // end switch
// marking kernel as normal
kernel_busy = 0;
}
/*!
\brief Invokes the scheduler
Increment systick counter, invoke scheduler and flag any context switching needed for PendSV to take care of.
*/
void SysTick_Handler(void) // 1KHz
{
os_KernelEnterCriticalSection();
// Increment systick counter
systick_count++;
// Run scheduler to determine if a context switch is needed
scheduler();
if (curr_task != next_task)
{
// Context switching needed
ScheduleContextSwitch();
}
os_KernelExitCriticalSection();
return;
}
/*!
\brief C part of the SVC exception handler
SVC 0 is initializing the OS and starting the scheduler.
Each thread stack frame is initialized.
\param svc_args Used to extract the SVC number
*/
void SVC_Handler_C(unsigned int * svc_args)
{
uint8_t svc_number, i;
svc_number = ((char *) svc_args[6])[-2]; // Memory[(Stacked PC)-2]
// marking kernel as busy
kernel_busy = 1;
switch(svc_number) {
case (0): // OS start
// Starting the task scheduler
// Update thread to be run based on priority
scheduler();
curr_task = next_task; // Switch to head ready-to-run task (Current task)
th_q_h = curr_task;
th_q[curr_task]->status = TH_RUNNING;
if (PSP_array[curr_task] == NULL)
{
// Stack not allocated for current task, allocating
i = curr_task;
th_q[i]->stack_p = (uint32_t) task_stack[i];
PSP_array[i] = ((unsigned int) th_q[i]->stack_p) + (th_q[i]->stack_size) - 18*4;
HW32_REG((PSP_array[i] + (16<<2))) = (unsigned long) th_q[i]->start_p; // initial Program Counter
HW32_REG((PSP_array[i] + (17<<2))) = 0x01000000; // initial xPSR
HW32_REG((PSP_array[i] )) = 0xFFFFFFFDUL; // initial EXC_RETURN
HW32_REG((PSP_array[i] + ( 1<<2))) = 0x3;// initial CONTROL : unprivileged, PSP
th_q[i]->stack_p = PSP_array[i];
}
svc_exc_return = HW32_REG((PSP_array[curr_task])); // Return to thread with PSP
__set_PSP((PSP_array[curr_task] + 10*4)); // Set PSP to @R0 of task 0 exception stack frame
NVIC_SetPriority(PendSV_IRQn, 0xFF); // Set PendSV to lowest possible priority
if (SysTick_Config(os_sysTickTicks) != 0) // 1000 Hz SysTick interrupt on 16MHz core clock
{
stop_cpu2;
// Impossible SysTick_Config number of ticks
}
__set_CONTROL(0x3); // Switch to use Process Stack, unprivileged state
__ISB(); // Execute ISB after changing CONTROL (architectural recommendation)
break;
case (1): // Thread Yield
// Run scheduler to determine if a context switch is needed
scheduler();
if (curr_task != next_task)
{
// Context switching needed
ScheduleContextSwitch();
}
__ISB();
break;
case (2): // Stack Allocation
// Create stack frame for thread
i = svc_args[0];
th_q[i]->stack_p = (uint32_t) task_stack[i];
PSP_array[i] = ((unsigned int) th_q[i]->stack_p) + (th_q[i]->stack_size) - 18*4;
HW32_REG((PSP_array[i] + (16<<2))) = (unsigned long) th_q[i]->start_p; // initial Program Counter
HW32_REG((PSP_array[i] + (17<<2))) = 0x01000000; // initial xPSR
HW32_REG((PSP_array[i] )) = 0xFFFFFFFDUL; // initial EXC_RETURN
HW32_REG((PSP_array[i] + ( 1<<2))) = 0x3;// initial CONTROL : unprivileged, PSP
th_q[i]->stack_p = PSP_array[i];
__ISB();
break;
default:
#if ((ENABLE_KERNEL_PRINTF) && (ENABLE_KERNEL_PRINTF == 1))
printf("ERROR: Unknown SVC service number\n\r");
printf("- SVC number 0x%x\n\r", svc_number);
#endif
stop_cpu2;
break;
} // end switch
// marking kernel as normal
kernel_busy = 0;
}
