tn_arch.h File Reference

Detailed Description

Architecture-dependent routines declaration.

Definition in file tn_arch.h.

Go to the source code of this file.

Functions
void	tn_arch_int_dis (void)
	Unconditionally disable system interrupts. More...
void	tn_arch_int_en (void)
	Unconditionally enable interrupts. More...
TN_UWord	tn_arch_sr_save_int_dis (void)
	Disable system interrupts and return previous value of status register, atomically. More...
void	tn_arch_sr_restore (TN_UWord sr)
	Restore previously saved status register. More...
TN_UWord *	_tn_arch_stack_top_get (TN_UWord *stack_low_address, int stack_size)
	Should return top of the stack. More...
TN_UWord *	_tn_arch_stack_bottom_empty_get (TN_UWord *stack_top, int stack_size)
	This function should return address of bottom empty element of stack, it is needed for software stack overflow control (see TN_STACK_OVERFLOW_CHECK). More...
TN_UWord *	_tn_arch_stack_init (TN_TaskBody *task_func, TN_UWord *stack_top, int stack_size, void *param)
	Should put initial CPU context to the provided stack pointer for new task and return current stack pointer. More...
int	_tn_arch_inside_isr (void)
	Should return 1 if system ISR is currently running, 0 otherwise. More...
int	_tn_arch_is_int_disabled (void)
	Should return 1 if system interrupts are currently disabled, 0 otherwise. More...
void	_tn_arch_context_switch_pend (void)
	Called whenever we need to switch context from one task to another. More...
void	_tn_arch_context_switch_now_nosave (void)
	Called whenever we need to switch context to new task, but don't save current context. More...
void	_tn_arch_sys_start (TN_UWord *int_stack, unsigned int int_stack_size)
	Performs first context switch to the first task (_tn_next_task_to_run is already set to needed task). More...

Function Documentation

void tn_arch_int_dis

(

void

)

Unconditionally disable system interrupts.

Refer to the section Interrupt types for details on what is system interrupt.

void tn_arch_int_en

(

void

)

Unconditionally enable interrupts.

Refer to the section Interrupt types for details on what is system interrupt.

TN_UWord tn_arch_sr_save_int_dis

(

void

)

Disable system interrupts and return previous value of status register, atomically.

Refer to the section Interrupt types for details on what is system interrupt.

See also

tn_arch_sr_restore()

void tn_arch_sr_restore

(

TN_UWord

sr

)

Restore previously saved status register.

Parameters

sr	status register value previously from tn_arch_sr_save_int_dis()

See also

tn_arch_sr_save_int_dis()

TN_UWord* _tn_arch_stack_top_get	(	TN_UWord *	stack_low_address,
		int	stack_size
	)

Should return top of the stack.

A stack implementation is characterized by two attributes:

• Where the stack pointer points:
  • Full stack: The stack pointer points to the last full location;
  • Empty stack: The stack pointer points to the first empty location.
• How the stack grows:
  • Descending stack: The stack grows downward (i.e., toward lower memory addresses);
  • Ascending stack: The stack grows upward (i.e., toward higher memory addresses).

So, depending on the stack implementation used in the particular architecture, the value returned from this function can be one of the following:

• (stack_low_address - 1) (Full ascending stack)
• (stack_low_address + stack_size) (Full descending stack)
• (stack_low_address) (Empty ascending stack)
• (stack_low_address + stack_size - 1) (Empty descending stack)

Parameters

stack_low_address	Start address of the stack array.
stack_size	Size of the stack in TN_UWord-s, not in bytes.

TN_UWord* _tn_arch_stack_bottom_empty_get	(	TN_UWord *	stack_top,
		int	stack_size
	)

This function should return address of bottom empty element of stack, it is needed for software stack overflow control (see TN_STACK_OVERFLOW_CHECK).

For details on various hardware stack implementations, refer to _tn_arch_stack_top_get().

Depending on the stack implementation used in the particular architecture, the value returned from this function can be one of the following:

• (stack_top - stack_size) (Full descending stack)
• (stack_top + stack_size) (Full ascending stack)
• (stack_top - stack_size + 1) (Empty descending stack)
• (stack_top + stack_size - 1) (Empty ascending stack)

Parameters

stack_top	Top of the stack, returned by _tn_arch_stack_top_get().
stack_size	Size of the stack in TN_UWord-s, not in bytes.

TN_UWord* _tn_arch_stack_init	(	TN_TaskBody *	task_func,
		TN_UWord *	stack_top,
		int	stack_size,
		void *	param
	)

Should put initial CPU context to the provided stack pointer for new task and return current stack pointer.

When resulting context gets restored by _tn_arch_context_switch_now_nosave() or _tn_arch_context_switch_pend(), the following conditions should be met:

• Interrupts are enabled;
• Return address is set to tn_task_exit(), so that when task body function returns, tn_task_exit() gets automatially called;
• Argument 0 contains param pointer

Parameters

task_func	Pointer to task body function.
stack_top	Top of the stack, returned by _tn_arch_stack_top_get().
stack_size	Size of the stack in TN_UWord-s, not in bytes.
param	User-provided parameter for task body function.

Returns

current stack pointer (top of the stack)

int _tn_arch_inside_isr

(

void

)

Should return 1 if system ISR is currently running, 0 otherwise.

Refer to the section Interrupt types for details on what is system ISR.

int _tn_arch_is_int_disabled

(

void

)

Should return 1 if system interrupts are currently disabled, 0 otherwise.

Refer to the section Interrupt types for details on what is system interrupt.

void _tn_arch_context_switch_pend

(

void

)

Called whenever we need to switch context from one task to another.

This function typically does NOT switch context; it merely pends it, that is, it sets appropriate interrupt flag. If current level is an application level, interrupt is fired immediately, and context gets switched. Otherwise (if some ISR is currently running), context switch keeps pending until all ISR return.

Preconditions:

• interrupts are enabled;
• _tn_curr_run_task points to currently running (preempted) task;
• _tn_next_task_to_run points to new task to run.

Actions to perform in actual context switching routine:

• save context of the preempted task to its stack;
• if preprocessor macro _TN_ON_CONTEXT_SWITCH_HANDLER is non-zero, call _tn_sys_on_context_switch(_tn_curr_run_task, _tn_next_task_to_run);.
• set _tn_curr_run_task to _tn_next_task_to_run;
• restore context of the newly activated task from its stack.

See also

_tn_curr_run_task

_tn_next_task_to_run

void _tn_arch_context_switch_now_nosave

(

void

)

Called whenever we need to switch context to new task, but don't save current context.

This happens:

• At system start, inside tn_sys_start() (well, it is actually called indirectly but from _tn_arch_sys_start());
• At task exit, inside tn_task_exit().

This function doesn't need to pend context switch, it switches context immediately.

Preconditions:

• interrupts are disabled;
• _tn_next_task_to_run is already set to needed task.

Actions to perform:

• if preprocessor macro _TN_ON_CONTEXT_SWITCH_HANDLER is non-zero, call _tn_sys_on_context_switch(_tn_curr_run_task, _tn_next_task_to_run);.
• set _tn_curr_run_task to _tn_next_task_to_run;
• restore context of the newly activated task from its stack.

See also

_tn_curr_run_task

_tn_next_task_to_run

void _tn_arch_sys_start	(	TN_UWord *	int_stack,
		unsigned int	int_stack_size
	)

Performs first context switch to the first task (_tn_next_task_to_run is already set to needed task).

Typically, this function just calls _tn_arch_context_switch_now_nosave(), but it also can perform any architecture-dependent actions first, if needed.